Viticulture

Grapes are a unique agricultural product. While more than half go toward the production of wine, they are also grown to be dried into raisins or eaten fresh. Grapes command more return per acre than almost any other plant, and in 2018, a single hectare of grand cru vineyard in Burgundy cost over seven million dollars on average. Further, unlike many crops that are planted each growing season, vineyards are a long-term investment—they require several years to become established and are designed to survive for decades.

Unlike many commodity plants, the profitability of wine grapes is driven by quality, which includes the grape’s ability to convey a unique sense of place. While other agricultural crops look to new varieties for flavor improvement, disease resistance, and adaptations to climate, most wine producers rely on a small number of established cultivars. Site selection and vineyard practices, however, are critical, since improvement is achieved through management of the vine’s environment.

Domestication of the Grapevine

Grapes were one of the first fruits to be domesticated by humans. In ancient times, they were prized for their high levels of sugar, a source of both nutrition and novelty. Most of the grape varieties used in wine production belong to a single species, Vitis vinifera, which was first domesticated from wild grapevines, called Vitis vinifera subsp. sylvestris (or Vitis sylvestris), at least 7,000 years ago in the land between the Black, Caspian, and Mediterranean Seas. As nomadic people settled into an agrarian lifestyle, they carried grapevines south to Mesopotamia. Domestic vinifera grapes were spread from the Fertile Crescent throughout the Mediterranean and Europe, driven by the westward migration of farming communities and, eventually, the expansion of the Roman Empire. Vitis sylvestris is native to Europe and Western Asia, and wild grapevines still inhabit these areas. Some evidence indicates that there may have been other centers of domestication of Vitis sylvestris, including sites in the Iberian Peninsula and Southern Italy. 

Over time, a collection of grape varieties was generated through the process of evolution, breeding, and human selection. Today, roughly 10,000 grape cultivars exist, with over 1,400 in commercial production, and grapegrowing has spread to hospitable zones throughout the world.

Grapevines are lianas: unlike trees, they do not produce extensive wooden support systems but are instead “structural parasites,” climbing on trees for support. They are also phototrophs, or sunseekers, and invest most of their energy into producing leaves and tall shoots, since rapid vertical growth is essential for competition with other plants for vital sunlight. In nature, grapevines invest little energy in fruit production, yielding just enough scraggly clusters to ensure proliferation. Wild vines are also dioecious, which means that both male and females plants exist, and successful fertilization relies on wind and insects for pollination. Male plants bare no fruit, and female plants are only fruitful when a male plant is nearby.

By contrast, since domesticated grapevines are cultivated for their fruit, they have been selected and managed to be prolific. Hermaphroditic, self-pollinating varieties were likely chosen initially, since these vines would have reliably produced more fruit. In addition to high yields, the selection of vines suitable for agriculture favored those with other beneficial characteristics, including large clusters, adaptations to the growing environment, and resistance to disease. The ability to attain the high sugar concentrations necessary for wine production, as well as taste, aroma, and appearance, also factored into selection. Analogous to a house cat and a lion, domestic vines have diverged significantly from those found in nature.

While the romantic notion of a vineyard paints it as a natural space with little intervention, it is more akin to a highly cultivated garden, organized for both ease of use and optimization of yields and fruit quality. Rows facilitate management and allow tractors and other equipment to access the vines easily. Grapes are propagated vegetatively, generally grafted to a different species’ roots, and trained into small shrubs to facilitate management. Annual pruning dictates the number of shoots that will form in the following year and where they will be located. Growers often impose moderately stressful conditions, such as limited water availability, to encourage the vine to limit its vegetative growth and concentrate its energy on fruit production. By taming and training them, humans have coaxed vines to defy their nature in order to be cultivated effectively for food and wine production.

Vine Anatomy

Grapevines are perennial, deciduous plants that have a permanent woody frame consisting of a trunk, cordons, canes, and spur positions. Below the ground, an extensive root system anchors the vine and provides an interface with the soil, which supplies water and nutrients to the plant. A vine’s root system is mostly located within the top three feet of soil and consists of mature roots, which survive year to year, and smaller feeder roots, which grow anew each year. Often, Vitis vinifera is grafted onto a phylloxera-resistant rootstock. Grafted vines consist of an above-the-ground portion called the scion, which is joined to the rootstock at the graft union, visible a few inches above the vineyard floor. Some rootstock species develop deep root systems, while others grow more laterally.

A grapevine’s trunk is analogous to that of a tree; it’s the permanent, vertical structure. Cordons, canes, or spur positions may be attached to the trunk, though the vine’s form will ultimately depend on pruning decisions made during the first few years of the vine’s life. 

Canes are shoots grown in the previous growing season that have lignified, or turned brown. After pruning, they are generally one to four feet long. Spurs, however, are canes that have been trimmed to a length of several inches. Cordons are horizontal extensions of the trunk and have a number of spur positions located along them. Along a cane, there are dormant buds, and spurs generally contain between one and three buds. During the growing season, these buds develop into fruiting shoots. Every few inches along each shoot, there are nodes, which resemble knuckles, and the portion of stem between nodes is called the internode. Leaves, buds, clusters, and tendrils are joined to each shoot at the node. Collectively, all of the vegetative green growth that develops during the growing season is called the canopy.

Two types of buds are located at each node, between the leaf and the stem: lateral buds and dormant buds. Each bud contains a highly compressed potential shoot. Lateral buds develop into shoots called laterals during the current growing season. These are side shoots that branch off of the main fruiting shoots. They are typically non-fruiting but may produce small clusters known as second crop. Laterals are often trimmed or removed through canopy management to prevent overcrowding and shading. Dormant buds, also called latent buds, spend the year maturing and develop into shoots in future years. As a rule, the dormant buds that formed last year, on canes and spurs from one-year-old wood, are the most fruitful. Dormant buds on older wood may also develop into unwanted shoots called suckers. Generally, suckers will not produce any fruit, and they are removed while they are small.

At each node, a single leaf develops, adjacent to the buds. Leaves are the powerhouse of grapevines, where photosynthesis takes place, and petioles are their stems, connecting leaf and shoot. 

Clusters are located at nodes near the base of the vine. Most shoots contain between one and three clusters, with two being most common, though the typical number varies by grape variety. Carignan, for example, is known for producing three clusters per shoot. The area of the vine where the fruit is growing is described as the fruit zone. Long, thin coils called tendrils support the vine by wrapping around and attaching to trellises, trees, or other supports. Technically, they are modified flower clusters, though the two bear no resemblance to each other. Clusters and tendrils develop along each shoot in a “hit, hit, miss” pattern. The first few nodes closest to the base of the vine typically have neither. Then, every two nodes have either a cluster or a tendril, while every third node has neither, with the pattern continuing up the shoot.

In the beginning of the season, inflorescences, or flower clusters that resemble immature grape clusters, are found on each fruitful shoot. These clusters were actually initiated within the buds during the previous growing season, with the number of clusters determined at that time. Every flower has the potential to be fertilized and become a berry during bloom, and flower clusters are transformed into grape clusters at fruit set. The stem of the cluster is called the rachis. Berries have a thick waxy coating known as bloom that protects the fruit from disease, prevents berry dehydration, and collects yeasts and other microbes useful during fermentation; within most berries are two or three seeds.

Ampelography is the science of identifying grape varieties based on morphology. Clusters and berries vary in shape and size, and, along with leaf characteristics and the vine’s overall growth patterns, these attributes are used to identify grape species and varieties based on their unique patterns.

Vine Balance

A vine with ample water and nutrients will develop a large canopy with fast-growing shoots. Vine vigor refers to the amount of vegetative growth produced by a vine, and it is assessed through several markers, including shoot length and diameter, the number of shoots per vine, and the vine’s tendency to produce laterals and suckers. Vigor may be quantified through pruning weight, which is literally the weight of the material that is removed from the vine at pruning, sampled across a selection of vines.

Excessive vegetative growth can be detrimental to fruit quality and quantity. Overly vigorous vines put too much energy into growing shoots and leaves, resulting in a large, shady canopy. Shaded buds will develop into less productive shoots, reducing the overall quantity of fruit over time and exacerbating the imbalance. Fruit quality is often compromised through increased disease pressure and lack of light in the fruit zone.

A vine’s capacity is the optimum amount of fruit, or yield, it is able to produce, given its specific conditions. Vines that carry too much fruit for their frame may not be able to successfully ripen it, especially in marginal climates, and will weaken over time, further reducing capacity. On the other hand, if too little fruit is left, the vine will become more vigorous, and the amount of fruit produced will gradually decrease. There is a general belief that balanced vines make balanced wines. Vine balance considers vegetative versus fruit growth. The Ravaz Index, the ratio of fruit weight to pruning weight, is one metric used for assessment. Ratios of 4 to 10 are generally considered balanced. Growers also look at the length of shoots and internodes, targeting three- to four-inch internodes and roughly four-foot shoots.

Growers coax vines toward balance through planting decisions, including choice of rootstock and trellis systems, as well as vineyard operations, such as pruning and irrigation. Balanced vines pay off, maximizing yields and fruit quality. Yet it’s important to recognize that balance can take many forms. Larger vines have more capacity for fruit production, and vines grown on fertile soils will have more vigor and thus more capacity than those grown on weaker soils. In this scenario, the vine may be more balanced carrying five tons per acre rather than half of that. Appropriate yields should not be prescribed without understanding the conditions of the site.

Grapevine Taxonomy

Vitis vinifera, also called the European grapevine, includes many of the wine and table grapes. It belongs to the family Vitaceae, along with other common vine plants like Boston ivy and Virginia creeper. Most cultivated grape species belong to the genus Vitis and have 38 chromosomes, while others belong to the genus Muscadinia, formerly considered a subspecies of Vitis, with 40 chromosomes. Beyond vinifera, several other Vitis species are significant in viticulture. Vitis rupestris, Vitis riparia, and Vitis berlandieri are common rootstock species, and Vitis labrusca, Muscadinia rotundifolia, and Vitis amurensis are occasionally used in winemaking. Within each species, there are many cultivars, often called varieties in a wine context.

Both species and varieties have been interbred. The offspring of two varieties belonging to the same species are known as crossings, and examples include Chardonnay, Riesling, Merlot, and almost all other cultivars used in winemaking. The products of interspecies breeding are called hybrids; rootstocks and niche wine grapes like Rondo, Chambourcin, and Vidal Blanc are examples. Crossings and hybrids have been bred to incorporate the desirable characteristics of both parents. For instance, Frontenac is a hybrid that combines the cold hardiness and resistance to fungal diseases of Vitis labrusca, with a flavor profile more similar to vinifera. (Labrusca varieties are often marked by a grapey flavor described as “foxy” that is generally not preferred in wine.) Throughout history, grape breeding has occasionally been intentional but more often occurs in nature. 

Cultivars 

Crossings of Vitis vinifera are responsible for the tens of thousands of cultivars that exist. Pinot Noir, Savagnin, and Gouais Blanc are old varieties, believed to be closely related to Vitis sylvestris, and found in the lineage of many common European grape varieties. Most crossings arose naturally, but a few well-known examples are products of breeding. The teinturier grape Alicante Bouschet, whose durability and deep color made it popular with home winemakers during Prohibition, was produced by crossing Petit Bouschet, also an intensely colored teinturier with thick skins, with fruit-forward Grenache. Müller-Thurgau, once a very important variety in Germany, was produced from Riesling and Madeleine Royale in an attempt to develop an earlier-ripening grape with Riesling-like aromatics. South Africa’s signature grape, Pinotage, was bred to combine the elegance of Pinot Noir with the hardiness and productivity of Cinsault.

From an evolutionary perspective, vinifera grape varieties are organized into three proles, indicating the primary center of their cultivation, evidenced by their physical characteristics. Proles pontica, which includes Zinfandel, Furmint, and Vermentino, is native to the Aegean and Black Seas and has more jagged leaf blades; white hair on the underside of the leaves; mid-sized clusters; and small-to-medium, round berries. Proles occidentalis is native to Western Europe and includes most international grape varieties, such as Cabernet Sauvignon, Chardonnay, Pinot Noir, and Riesling. Occidentalis has convex leaves; small, compact bunches; and small, round berries. Proles orientalis is native to the Middle East, Iran, and Afghanistan and has large leaves, bunches, and berries with an oval shape. Muscat, Cinsault, and most table grape varieties are examples.

Grape varieties differ significantly from one another, both in terms of wine flavor and environmental adaptations, as a result of their unique genetics. Every variety is hardwired to produce different amounts of flavor, color, and tannin. The chemical pathways that create each of these may be upregulated, where the production of a compound is increased, or downregulated, where that production is decreased, in response to the environment. For example, grapes under water stress will produce more tannin than those with an ample water supply, even after accounting for the difference in berry size. Varieties also exhibit different behavior. Some go through budbreak a couple of weeks earlier than others, some require more heat accumulation in order to achieve ripeness, and varieties differ when it comes to yield potential, vine vigor, and tolerance to environmental stressors.

The grape varieties are usually divided into red (or black) and white grapes, though pink (or gray) versions exist as well, such as Gewürztraminer and Pinot Gris. White grapes can be further characterized as aromatic, partially aromatic, and non-aromatic, primarily resulting from the grape’s propensity to form monoterpenes, compounds responsible for flavors of rose, lychee, and orange blossom. Red grapes differ in their amount of color and its hue. In both cases, levels of acidity and tannin vary, and each grape has a unique flavor profile. 

Clones

Clones are variants within a grape variety that differ slightly in terms of morphology or behavior. Grapevines are prone to mutations that arise from errors during cell division, and the genetic variation that results is the major source of clonal differences. Mutations can affect a single bud, leaf, or flower. When a bud is affected, the single resulting shoot may bear some distinction from the parent vine. Cuttings taken from this shoot would constitute a unique clone that may differ from the parent plant in terms of grape color, ripening dates, yields, berry and cluster morphology, and flavor characteristics. Viral infection also influences gene expression and is another source of clonal variation. The Gingin clone of Chardonnay that is popular in Western Australia, for example, was confirmed to have grapevine leafroll virus, believed to be responsible for some of its positive attributes, including low yields. When clonal selection is performed in a nursery, virus-infected vines are heat-treated to remove the virus before they are propagated and distributed. 

Old varieties typically exhibit more clonal diversity. Pinot Noir is thought to be at least 2,000 years old, and as a result, many diverse clones exist. As mutations accumulate over time, significant changes may result in the mutant being renamed as an entirely different variety. Pinot Gris, Pinot Blanc, Pinot Meunier, and Pinot Teinturier are considered by many to be separate varieties, but each is technically a clone of Pinot Noir. Similarly, the highly aromatic, pink Gewürztraminer is a mutation of Savagnin Blanc. 

Hybrids

Hybrid grape varieties allow for viticulture in environments where grapes would not otherwise grow successfully. In America in the early and mid-1800s, vinifera was interbred with native American grape species like Vitis labrusca and Vitis aestivalis that are better adapted to the cold winters and humid, disease-prone summers of much of the Eastern United States. The resulting hybrid varieties include Clinton, Concord, Catawba, Delaware, Herbemont, Isabella, Niagara, Noah, and Norton. While some of these are used for wine, many are considered better suited to fruit juice and jam on account of their foxy flavors. Hybrids tend to be high yielding, and the resulting wine is generally regarded as inferior to that of pure Vitis vinifera. 

After the introduction of phylloxera and powdery and downy mildews to Europe, French researchers looked to hybrids to instill pest and disease resistance until better treatments were found. Beginning in the late 1800s, a large number of French hybrids were generated, including Baco Noir and Blanc, Chambourcin, Chancellor, Couderc Noir, Plantet, Villard Noir and Blanc, Seibel, and Seyval Blanc. These played an important role in European wine production from the late 1800s until the mid-1900s. By the end of the 1950s, hybrid grapes covered one-third of France’s vineyard area. Subsidies encouraged producers to replant vineyards to vinifera grapes, and by the late 1980s, hybrid varieties accounted for only 3% of European production. Today, most hybrids are not permitted by the EU for PDO wine production, though exceptions exist. The German Rondo and Regent, used for their disease resistance and cold tolerance, are most common.

French hybrids like Vidal Blanc, Vignoles, Chambourcin, Seyval Blanc, and Maréchal Foch are more typical in vineyards in Eastern and Midwestern North America, along with newer varieties like Cayuga White, Chardonel, Frontenac, and Traminette, which were bred to withstand winter freeze. Japan’s signature grape, Koshu, is a vinifera-dominant hybrid crossed with the East Asian species Vitis davidii. Hybrid grapes are considered by some to be more sustainable, since many are disease resistant and require significantly less use of fungicides.

Rootstocks

When a vine is grafted, some characteristics of the rootstock are conferred to the scion. While rootstocks were first developed for phylloxera resistance, today, they have other adaptations that may be beneficial to a vine, as they differ in terms of vigor, drought tolerance, resistance to pests and diseases, and adaptations to various soil conditions.

Most rootstocks are hybrids of non-vinifera grape species, especially North American varieties. Three species are frequently encountered: Vitis riparia, Vitis rupestris, and Vitis berlandieri. Other examples include Vitis champinii, Muscadinia rotundifolia, and Vitis solonis. Offspring of these species usually demonstrate characteristics inherited from both of their parents. By knowing the general attributes of each, the behaviors of their offspring can be better understood.

• Vitis riparia is native to riparian areas, or those alongside rivers, throughout much of eastern and central North America, where it grows up trees. Because its native habitat is near water, riparia forms shallow, fibrous roots and is not drought tolerant. Riparia induces low vigor and early ripening in the scion and confers phylloxera resistance. It is easy to propagate but does not do well in lime soils. Riparia Gloire is a pure riparia rootstock.
• Vitis rupestris is native to the American South. A shrubby vine that thrives in rocky creek beds and nutrient-poor areas, it grows extensive roots, resulting in drought tolerance in deep soils. Rupestris is vigorous and will induce large canopies in the scion when planted on fertile soils. It is resistant to phylloxera and somewhat tolerant of nematodes and viruses, so it may result in less virus expression. Rupestris is easy to propagate. St. George is a pure rupestris rootstock.
• Vitis berlandieri is native to deep limestone soils in Texas and a good choice for use on alkaline soils. Berlandieri develops deep roots and confers some drought tolerance. It induces later ripening and has variable phylloxera tolerance. Berlandieri vines will not root from dormant cuttings so must be bred with another vine in order to be commercially viable.

Climate

The environmental conditions within the vineyard play an important role in shaping wine expression. This phenomenon has been described as terroir. While terroir has been interpreted literally to refer to vineyard soils, most definitions have expanded to encompass the influences of climate, topography, human practices, and sometimes other external biological factors such as microorganisms and virus. Whatever the precise definition, terroir is broadly understood as the elusive quality that gives a wine a sense of place and makes it a more intriguing, unique product.

The vine’s environment fosters its growth and development. Because a vine is not able to move, it must instead adapt. These adaptations often manifest themselves as differences in fruit characteristics. As an example, water-stressed vines will develop a smaller canopy that provides less shade to the fruit. Along with a host of other differences in fruit composition, berries that develop in the sun will produce more “sunscreen” phenolic compounds. Fruit ripening dynamics, and the amount of sugar, acid, tannin, and flavor, are all impacted by environmental conditions. It is for this reason that wine is often said to reflect the place in which it’s grown.

Climate refers to the patterns and overall amount of heat, sunlight, precipitation, and wind that characterize a region. A related and often confused concept is weather, which describes these properties over a short period. Climate is the long-term average of weather over time. It is often separated into three spheres of influence: macro-, meso-, and microclimate. Macroclimate describes the climate of a larger region, spanning tens to hundreds of miles. While not well defined, mesoclimate identifies a smaller area, a single vineyard or a region that perhaps spans tens of miles and might be impacted by local geographical features like smaller bodies of water, topography, and soil conditions. Microclimate describes the environment directly around the vine and fruit. While this is influenced by the vineyard site, human practices such as trellis systems and canopy management play an important and often underappreciated role in shaping the environment. 

While some climates are inhospitable to grapegrowing, many grape varieties can be grown in a range of climates and soil types. Chardonnay, for example, grows successfully across disparate regions, as it can be appreciated in a range of styles. Each climate, of course, offers its own unique challenges. Grapes grown in climates that are too warm may ripen early, at the detriment of flavor and acidity, while grapes grown in cool climates may not ripen sufficiently, also impacting flavor. Wet climates may have elevated disease pressure, while overly dry climates may not provide enough water to sustain growth.

Climate Classifications

Climate classifications consider patterns of temperature and precipitation to give a high-level synopsis of weather patterns and potential hazards. They are a convenient means of comparing regions to one another. While grapes are often associated with Mediterranean climates, some wine regions are better described as maritime, continental, or even subtropical. Mediterranean and maritime climates are moderate, with a small range between summer and winter temperatures. Continental climates have a more dramatic temperature swing throughout the year and experience the classic four seasons. Mediterranean climates have wet winters but receive little rain during the growing season, while maritime and continental climates receive rain year-round. Burgundy, Austria’s Wachau, and Mendoza are typically considered continental; Bordeaux, New Zealand’s Hawkes Bay, and Oregon’s Willamette Valley are maritime; and Tuscany, the Barossa Valley, and Stellenbosch, South Africa, are best described as Mediterranean. While labels are convenient, it’s useful to think of these classifications as a spectrum, with most regions falling in between specific definitions.

Vines are temperate plants and require a dormant season prior to budbreak. As a result, climates without sufficiently cold winter temperatures are not suitable for wine grape production. Tropical climates, for instance, have little temperature variation throughout the year and are not suited to wine grapes, but there are subtropical regions where grapegrowing occurs, including parts of eastern Australia, Madeira, and the Canary Islands. Often, grapes grown in these climates are made into fortified wines, where the effect of the vineyard site is arguably less important than the impact of winemaking. 

In the EU, wine regions are classified into zones depending by climate, and certain practices including chaptalization, acid adjustments, and minimum potential alcohol requirements are governed by zone. Germany, the Loire, Champagne, Alsace, and Austria belong to Zones A and B, which are permitted to enrich wine by 3% ABV and deacidify, but not acidify. Portugal, Southern Spain, Southern Italy, and parts of Greece belong to Zone CIIIb. They may acidify, but not deacidify, and enrich to a lesser extent. 

The Köppen-Geiger climate classifications divide regions into five main groups—tropical, dry, temperate, continental, and polar—and then further into subgroups based on temperature and precipitation patterns. Under this scheme, most winegrowing regions are categorized as temperate. While this is a very precise and well-defined index, it is seldomly referenced in regard to wine.

Environmental Factors

Differences in climate can be distilled into a few key properties that are fundamental to a vine’s development: heat, light, water, and nutrients. Without sufficient amounts of each of these, a vine will not be fruitful and, in extreme cases, cannot survive.

Temperature 

It has been said that temperature is the metronome of plants. Heat drives vine growth and development, and many of a plant’s metabolic processes are temperature dependent. In warm climates, vines grow and develop more quickly, and fruit ripens earlier. Vine growth occurs between 50 and 95 degrees Fahrenheit, where mid-70s Fahrenheit is optimal. At lower temperatures, vines are dormant, and at temperatures over 95 degrees, vine growth and fruit ripening may shut down to conserve water. In hot weather, the microclimate around the canopy may actually be significantly cooler than the ambient temperature, as the vine cools itself through transpiration provided that it has a sufficient supply of water. Frigid temperatures can lead to injury and even vine death if precautions are not taken. 

Temperature affects both the quality and quantity of grapes. At bloom, it impacts the number of berries that will develop in the current growing season as well as the number of clusters that form the following year. Warmer temperatures result in higher yields, and vines will develop more capacity to support the additional crop. 

Understanding a growing region’s temperature profile, which includes both the overall amount of heat and patterns of accumulation, helps growers predict which grape varieties will be most successful. Varieties differ in the amount of heat needed to ripen. It is often claimed that the best quality wine comes from marginal climates where heat accumulation is just sufficient to ripen the grapes, with classic illustrations being Pinot Noir in Burgundy and Riesling in the Mosel. Flavor profiles are impacted, too. Warmer climates tend to yield fruitier wines, with higher alcohol, lower acidity, and softer tannins, but overripeness is a risk if harvest occurs later in the season. In cooler climates, wine may have lower alcohol, higher acidity, more astringent tannins, and fresh fruit and savory flavors; in some years, however, wines may be underripe and lacking flavor. 

Heat indices are used to guide varietal selection and to compare climates, estimating the amount of heat that accumulates throughout the growing season as the product of temperature and time. In the United States, the Winkler Index is frequently used to categorize viticultural areas with similar accumulation of “growing degree days” from April 1 to October 31. A region’s degree days are calculated by taking the average daily temperature minus 50 degrees Fahrenheit from every day within this range and summing them. The correction of 50 degrees is used to acknowledge that below this temperature, little shoot growth takes place. The Winkler Index is easily employed, but because it does not account for day length, it is not applicable to all regions. Elsewhere, the Huglin Index, which accounts for latitude, is more common.

While heat summation is a useful metric, the pattern of heat accumulation is also important. A moderate climate with a long growing season may experience the same overall heat accumulation as a warmer climate that has a short season, but each will impact the fruit differently. Two important concepts related to heat accumulation patterns are continentality and diurnal shift. Diurnal shift describes the difference between day and nighttime temperatures. In warm climates, a large diurnal shift is often thought to be important for wine quality as it seems to preserve acidity and flavors. In marginal climates, warm nights may assist in developing acid and flavors.

Continentality is the difference between summer and winter temperatures. Continental climates have wide temperature swings throughout the year and are more prone to spring and fall frost. Continentality can be assessed by comparing the average temperature during the warmest and coolest months of the year.

Light 

Sunlight is essential for plant growth. Light in the canopy fuels photosynthesis, which drives plant growth and development and creates sugar that facilitates fruit ripening. The number of sun-exposed leaves on a vine will determine its photosynthetic capacity, where more leaves results in a higher capacity for development, as well as greater water use. About 12 to 16 leaves are required to ripen a cluster. 

Metered, or dappled, sunlight improves fruit quality and quantity. Shaded buds are lessl fruitful, but ample light exposure on the shoots increases yields in the following year. Shaded berries ripen more slowly, while berries with direct light exposure can reach high temperatures, which may interfere with ripening. During a heat spike in 2017, one Napa Valley vineyard observed temperatures in excess of 140 degrees Fahrenheit in sunlit berries. Though light determines the rate of photosynthesis and therefore sugar accumulation in the fruit, other features of ripening, like acid degradation and tannin ripening, may be more tied to temperature.

Sunlight is typically considered important for flavor development. Light stimulates the production of phenolic compounds, like anthocyanin and tannin, that are considered key for red wine quality, as well as 1,1,6,-trimethyl-1,2-dihydronapthalene (TDN), the petrol flavor observed in aged Riesling. It also encourages the breakdown of pyrazine, the green bell pepper flavor associated with grapes such as Cabernet Sauvignon and Sauvignon Blanc. While sun exposure upregulates the production of certain flavor compounds, the increase in temperature can result in flavor loss, acid degradation, and sunburn. 

The duration of sunlight during the day (sunshine hours) and its intensity influence vine and fruit development. Vitis vinifera is said to require at least 1,250 sunshine hours to ripen fruit. Higher-latitude regions have longer days and receive more sunshine hours, while the sunlight intensity is greater nearer to the equator. Sunlight intensity also increases with elevation, but cloud cover, pollution, and smoke can reduce the amount of sunlight that reaches the vine. 

Water 

Vines are incredibly resilient plants and have adapted many mechanisms to survive and potentially thrive in periods of drought. While moderate water stress is considered beneficial for wine quality, all plants need water to grow and develop optimally. Vines generally require 10 to 30 inches of rain during the growing season, though more may be necessary depending on the timing of precipitation, temperature patterns, and soil conditions. Sandy soils with low water-holding capacity, warm climates, and high-density plantings require more water. Young vines also need more frequent water additions than mature vines, as their roots are not fully developed and they cannot access water stored at deeper soil depths. Many regions receive insufficient precipitation during the growing season and rely on irrigation.

Too little water can stunt growth and development, limit yields, and delay ripening. Under severe water stress, vines close their stomates to conserve water, halting photosynthesis and plant function. Extreme drought conditions result in defoliation and, eventually, vine death. Yet wet conditions can result in excessive yields and slow ripening and encourage the vine to produce a big, vigorous canopy. 

Timing is also important. An adequate amount of available water is desired early in the season so that shoots reach their full height prior to veraison, when berries change color. Once berries have formed, mild water stress helps to maintain a moderate berry size and promotes the production of phenolic compounds, which are considered integral to red wine quality. Near the end of the season, water deficit can cause dehydration, but rain near harvest can cause berries to swell and split, resulting in dilution and increased disease pressure. Late-season rain frequently reduces wine quality.

The amount of water available to the vine depends on soil conditions. Soil has a limited capacity to hold water. Heavy rainstorms can deposit a lot of water, but it may not be accessible to the vine, as some is lost through drainage or run-off. On deep soils, well-developed and deeper root systems allow a vine to source water from a larger volume of soil; shallow soils are more limited in their capacity. 

The impact of water availability on vine and fruit development, and especially on wine quality, is one of the most important topics being studied in viticulture today. By providing just enough water when the vine needs it, viticulturists hope to improve wine quality and conserve precious resources.

Wind 

Wind has a cooling and drying effect that can impact vine development. While this may help minimize disease pressure, vines may require more water, as leaves close their stomates under windy conditions to conserve water lost from the plant through transpiration. This leads to less vigorous vines and, in extreme situations, can result in delayed development. It is particularly difficult to establish a new vineyard in very windy conditions. In some instances, vine shelters and windbreaks can help protect the nascent shoots and leaves.

Along with windbreaks, other protective measures can be taken in windy climates. In Provence and the Southern Rhône, the vineyard rows may be planted parallel to the prevailing wind, with vines trained low to the ground, in order to minimize damage. In parts of coastal California, some producers have observed that rows planted perpendicular to the wind will “self-shelter,” resulting in higher sugar accumulation. Regions like Greece’s Santorini and Lanzarote in the Canary Islands have developed novel vine training systems for wind protection.

Geographical Factors

Latitude 

Wine grapes generally grow between 30 and 50 degree in latitude. In lower latitudes, the vines don’t experience a dormant season, while higher latitudes are often too cold for grapes to attain ripeness, or vines may be threatened by winter freeze. Both temperature and sunlight intensity are generally higher for regions closer to the equator. Those regions further from the equator often have shorter growing seasons but longer days, which accelerates growth and development. Marginal climates may also rely on other influences that increase their viability. For instance, higher latitudes often rely on warming from bodies of water, favorable orientations, and warm air currents, while lower latitudes may benefit from cooling influences like high elevation. 

Hills & Mountains 

Hills and mountains can result in significant climatic diversity. The first relevant factor is altitude, which tends to reduce temperature but also increases sunlight intensity. Roughly, for every 300-foot gain in elevation, the temperature will decrease by about 1 degree Fahrenheit, and for every 1,000-foot increase, there is a 2% increase in sunlight exposure. Because cold air sinks, lower-elevation bowls trap cold air and may be more frost prone. Gravity causes soil and water to run downhill, so the bottom of the hill typically has deeper soil and more available water. Mid-slope sites are often considered best for wine quality, as they seem to have an ideal balance of soil and water conditions, along with favorable airflow to prevent frost and disease. 

Elevation plays a key role in diurnal shift, especially in areas prone to marine influence. Vineyards above what’s commonly called the inversion layer tend to see smaller diurnal shifts, while vineyards below this layer warm during the day and cool, sometimes drastically, at night.

Some parts of a hill are warmer and sunnier than others. Slope, or the degree of incline, is an important factor. In Côte Rôtie, inclines can exceed 55 degrees. Vineyards in the Mosel reach 70 degrees—these are considered the steepest in the world. While the sun’s position changes throughout the day and year, steeper slopes will intercept the most sunlight on average and tend to be earlier ripening. (Solar panels are positioned at an angle for the same reason.) In Burgundy, grand cru vineyards are often located mid-slope, on the steepest and earliest-ripening part of the hill.

Aspect, or orientation, is the cardinal direction that the vineyard faces. In the Northern Hemisphere, south-facing vineyards intercept the most sunlight during the day, are warmer, and usually ripen earlier than north-facing vineyards, which tend to be the coolest sites. East-facing vineyards get more morning sun, reducing early morning humidity and thus minimizing disease pressure, while west-facing vineyards are exposed during the most intense part of the day, making them more prone to sunburn. Historically, south- and southeast-facing vineyards were preferred, as these conditions facilitate ripening. Mountain ranges tend to have a windward side that experiences more weather and precipitation, with a leeward side that is drier and more protected. Alsace and Mendoza, for instance, are both located in the rain shadows of nearby mountain ranges and receive relatively little precipitation.

Bodies of Water

Many historic winegrowing regions are situated along bodies of water, as this positioning provided a means of transport as well as groundwater or a source of irrigation. As with hills, where a vineyard lies in relationship to an ocean, lake, or river will affect its climate. Water has a large heat-holding capacity and changes temperature slowly. As a result, proximity to bodies of water results in a more moderate temperature range on both a daily and annual basis. Water can also reflect sunlight onto the vines, helping vineyards to ripen earlier. 

Air currents that move along water can bring cold or warm air into a region and create fog and mist that reduce the amount of sunlight reaching the vines. Viticulturally important examples include the cooling Humboldt Current off of Chile and Benguela Current in South Africa. The Gulf Stream warms much of Northern Europe, allowing grapes to ripen in locations where they otherwise might not. 

Humidity is often higher near water, and this can increase disease pressure. In some cases, this is beneficial, as in morning fog that helps develop noble rot in regions known for their botrytized wines.

Climate Change 

The wine business tends to be fixated on the weather due to its profound impact on vintage variation. Because of this, grapes are considered a more sensitive barometer of climate change than other crops. The industry has collected detailed records that illustrate changes over the past 50 years, including in heat accumulation, temperature extremes, and rainfall patterns. In some areas, drought and fire are more rampant than in the past. Changes in climate could redefine quality potential and wine style in classic regions throughout the world. Thus far, they have benefited some areas. Southern England was once considered unsuitable for grapegrowing but is now showing promise for sparkling production. Classic regions in Italy, France, and Germany are producing great vintages more consistently.

Alongside any effects of climate change, significant adjustments in viticultural practices over the past 50 years have also played a role in shifting wine styles. Not long ago, many regions struggled to adequately ripen grapes. As a result, viticulture developed practices specifically intended to accelerate the ripening process, and these were widely adopted. Producers developed more efficient canopy architecture, reduced yields, irrigated less, adopted earlier-ripening clones and rootstocks, and removed diseased vines that delayed ripening. The effect of these changes on grape ripening and wine style should not be underestimated.

Today, producers are looking to viticultural practices to slow ripening. Cooler sites that were historically less desirable, like those with a north-facing aspect, may be preferred in the future. In some cases, producers are even looking to new varieties; in Bordeaux, a proposal to allow seven new grape varieties in AOC wines was put forward in 2019.

Weather Hazards

Frost

Spring frost can kill young shoots, and while new shoots will often replace the lost ones, their development is delayed and they are typically less fruitful. Frost that occurs in the fall prior to harvest will kill the leaves, which prevents the vine from being able to ripen fruit further. In this case, the fruit will not improve and should be picked right away. These frost events are often the result of an inversion layer, where cold air near the ground is trapped under warmer air.

There are several means of frost mitigation:

• Site selection: Because cold air settles into areas of low elevation, especially bowls that have no way of draining, early-budding (and therefore frost-prone) varieties should be avoided on these sites.
• Air circulation: Cover crops and plants growing on the vineyard floor should be mowed short prior to frost season to allow for better air circulation.
• Sprinklers: Overhead sprinklers can be used to warm the surface of the vine by a few degrees. As water freezes, it releases heat, so as long as water is constantly applied during a frost event, the temperature will remain just above freezing.
• Fans or helicopters: These disrupt the inversion layer to warm the environment.
• Heat: Heaters and small fires are used to warm the microclimate. Many areas have banned the use of orchard heaters or “smudge pots” due to air quality concerns.
• Pruning methods: Vines may be pre-pruned, where spurs are left long, or late-pruned. This encourages sacrificial buds to push early in the season, knowing that a later pruning will remove damaged tissue.

Winter freeze can cause damage to dormant vines if temperatures fall below 5 degrees Fahrenheit. The methods described above only increase the temperatures slightly so are insufficient for protecting against winter freeze. Most vinifera vines can survive until 0 degrees Fahrenheit, but much below this, they risk death. In regions where winter freeze occurs, cold-tolerant varieties like Riesling and select hybrids may be planted. Otherwise, vines are buried each year for insulation and uncovered the subsequent spring. Recently, some producers have begun covering the vines in geothermal, geotextile blankets as an alternative means of freeze protection.

Hail

Hail regularly causes major localized damage in susceptible regions, including parts of the Loire Valley, Burgundy, Bordeaux, Piedmont, and Mendoza. Its impact on a particular growing season is dictated by the intensity of the event and the phenological stage of the vine. Hail can remove entire shoots and severely damage fruit as well as leaves, reducing the canopy’s capacity to support fruit ripening. Some regions have started using netting to protect the vines from hail. Another method is to fire hail cannons or rockets into the air, disrupting hail formation.

Drought

Many vineyards that thrived in the past now struggle due to lack of water. As with many weather hazards, site selection is key to limiting drought risk. Where it is possible, irrigation can help mitigate damage. Many wine regions in the EU that did not previously permit irrigation, including Bordeaux, Burgundy, Barolo, Barbaresco, and Montalcino, now allow it when faced with drought conditions, though additional restrictions may apply. Drought-tolerant rootstocks such as St. George, 110R, and 140R can also be used to better adapt the vine to its environment.

Risks of warm, dry environments include sunburn, which results in caramelized flavors, and dehydration, which concentrates sugars and acid in the fruit and can lead to raisinated flavors. Except in extreme cases, the risk of dehydration is typically not until later in the season, when the fruit has begun softening. Maintaining a protective canopy can help reduce the risk of sunburn, and where this is not possible, growers are increasingly using shade cloth, or fabric that is hung in the fruiting zone after veraison, to protect the fruit from dehydration and sunburn later in the season. In extreme heat events, sprinklers or misters might be used for evaporative cooling. In Australia, some producers apply a clay-based “sunscreen” to the fruit and canopy for protection.

Fire 

Forest fires that occur near wine regions are a growing problem. While vineyards often act as firebreaks and aren’t likely to burn themselves, smoke can be taken in through pores in the grapes or leaves and then translocated to the fruit any time after fruit set. This will taint the wine with an unpleasant, smoky flavor. The West Coast of North America, much of Australia, and parts of Portugal and Spain have all suffered damage from smoke in recent years. Although researchers are currently devoting attention to this topic, currently, there is no successful form of mitigation in the vineyard.

Soil

While a region’s weather varies from year to year, soil is reasonably stable. In this sense, it is the most enduring aspect of a wine’s sense of place. The basic function of soil, with respect to the vine, is to anchor it and provide it with water and nutrients. Soil conditions determine how much precipitation actually reaches the vine, since different soils absorb and hold water differently. Most critical to wine quality, soil characteristics impact vine vigor, which is driven by the availability of water and nutrients. 

Vines grown in favorable soil conditions will have deep roots and balanced vigor and are able to adapt to wet and dry conditions more easily. Free-draining soils with limited but adequate water and nutrients are best for wine quality. Highly fertile soils induce too much vigor and are typically avoided, as are soils with toxicities, including high salt or aluminum concentration. 

Popular Geology

As the notion of terroir has been popularized, vineyard soils have become a topic of interest for many wine enthusiasts. Wine descriptions often include information on rocks and soils found in the vineyard, such as their composition, geological age, and origins. 

Vineyard soils are often described by the qualities of their underlying bedrock. All rocks are classified into three types as determined by the geologic forces that formed the parent material:

• Igneous rocks like granite are formed from cooled magma and tend to be strong, resistant to erosion, and non-porous. Volcanic rocks are a type of igneous rock formed from lava. Basalt is a volcanic rock that breaks down to form highly fertile clay soils.
• Sedimentary soils are formed from weathered rocks carried by wind or water and deposited in layers. Limestone, chalk, shale, and sandstone are examples. The characteristics of these soils depend on what they’re made of and how strongly they’ve been cemented together.
• Metamorphic rocks are igneous or sedimentary rocks that have been subjected to heat and pressure. The category includes slate, schist, and gneiss. These rocks may be crumbly and friable or very hard, depending on the forces that shaped them and the underlying rocks’ composition.

While these types of rocks are often encountered in wine studies, the information they provide is limited, since these convenient classifications often combine dissimilar soils within a single category. Two vineyards with similar bedrock may have entirely different soils overlaying them. For example, a vineyard with granite bedrock could be overlaid with deep sandy soils or very thin soils. From a viticultural perspective, soils are characterized instead by their physical and chemical characteristics, since these properties determine the amount of water and nutrients available to the vine. 

A soil’s geological age, which generally refers to the time period when the underlying bedrock formed, is another property that is frequently cited in wine literature. The Kimmeridgian soils developed during the Jurassic Period from marine sediments, for example, are often noted, as they famously appear in Chablis, the Aube region of Champagne, and Sancerre. Just as there is huge diversity in soil today, the sediments laid down during the Jurassic Period were not homogenous; to describe a soil by the time its parent material was formed, while interesting, is not terribly meaningful.

Physical Properties

Great wines are made from grapes grown on a range of soil types. Within individual regions, producers frequently attribute wine qualities to the rocks found in their vineyard, but more generally, rock type does not appear to be well correlated with wine’s composition or attributes. While different soils clearly contribute to creating distinct wines, many of the differences ascribed to rock type are actually the result of physical attributes of the soil. 

A heterogenous mixture, soil is comprised primarily of minerals, water, air, and a small portion of organic matter. It’s made from weathered rock, plant material, and soil microbes. Soil’s formation is said to depend on five factors: the parent material, climate, topography, organisms, and time. The hardness of the parent rock will determine how easily it is broken down into soil. Warm, wet conditions will accelerate the weathering process, and the erosion that occurs by water and wind will be shaped by an area’s topography. Rocks and organic matter are broken down by the action of soil microbes and plants’ roots. This occurs slowly: it takes at least 100 years to form an inch of topsoil. Because soils are also transported by erosion, wind, leaching, and the action of rivers and glaciers, vineyards that share a common bedrock composition can have very different soils overlaying them.

Soils are organized into layers of sediments called horizons. Topsoil, or horizon A, is the outermost layer and ranges in depth from a few inches to a few feet. The composition of soil in this layer least resembles the composition of the underlying rock, since it has often been deposited from elsewhere. The topsoil contains most of the soil’s organic matter, worms, and microbes. Humus, an important topsoil constituent, is nutrient-dense organic material that holds water and nutrients in the soil, reduces erosion, and helps avoid soil compaction. As rainwater moves through the soil, it leaches smaller particles and nutrients downward. As a result, horizon B, called the subsoil, is less porous, contains a higher proportion of clay, and has better water-holding capacity than the topsoil. Horizon C, or the substratum, may consist of friable rock, and few if any roots are found here. Bedrock, which lies underneath the soil, is not soil at all but the outer layer of the earth’s surface. The manner in which roots navigate this complex layering of soil strata dictates the amount of water and nutrients the plant can access all year long. 

Soil is a reservoir of water for plants. After a rain event, water is lost through run-off, drainage, evaporation, and plant use. Several attributes influence how water drains and is stored in the soil to be used in the future. Soil depth, or the distance from the soil surface to the bedrock or another impenetrable layer, limits a vine’s rooting depth, which determines the deepest soil that the vine can access. (Roots may, however, be able to penetrate small cracks in friable bedrock.) Deep soils allow roots to access water from greater depths and provide the vine with more water throughout the growing season since the roots are in contact with a larger volume of soil. Because grapevines can develop deeper root systems than most other plants, on these soils, they can access water few competing plants are able to reach. Shallow soils can flood easily and have less available water than deeper soils; they require regular additions of water, sometimes through irrigation, to meet the vine’s needs. Shallow soils are generally not suitable for dry-farming except in climates that receive regular precipitation. Where an impenetrable layer, such as a hardpan, limits the rooting depth, the soil may be ripped prior to planting. Ripping involves dragging a large steel implement through the soil to break up an impenetrable layer. If shallow soils overlay bedrock, ripping is not possible, although modern heavy machinery, including excavators and pneumatic rock breakers, has allowed viticulture to extend into otherwise unusable land.

Two related concepts are key to healthy plant growth: porosity, or the amount of open space in the soil, and permeability, which describes the ability for water, oxygen, and roots to pass freely. These factors allow for drainage, water storage, root growth, and aeration, which are essential for healthy roots and soil microbial populations. Growth will be limited in waterlogged and non-porous soils. Porosity is governed by soil structure, an attribute that describes how soil particles aggregate, or form small clumps, and how easily these clumps crumble. Large pores between soil aggregates increase the porosity of well-structured soils and ensure that water on the soil surface is absorbed. These soils are better able to resist erosion and compaction. A moderate humus content helps the soil stick together, which improves the soil’s integrity. By increasing soil organic matter through the addition of compost and usage of cover crops, it is possible to build better structure in the soil.

Soil texture also influences porosity and permeability. Texture, referring to the size of soil particles, includes sand, silt, and clay, where sand particles are largest and clay smallest. Loam is a mixture of the three types and falls on a spectrum depending on the proportion of each component. Soils also contain rocks of different sizes, including gravels, pebbles, cobbles, and boulders. Rocks do not contribute water or minerals to the vine, but they increase drainage and limit erosion. They are generally considered beneficial for vine roots, when not overwhelming in proportion.

Sandy soils are sometimes called light soils, while clay soils are described as heavy, a reference to their superior water-holding capacity. Water is held in the soil by sticking to the surface of soil particles and through capillary action (the attraction of water molecules to each other and other substances), which is more effective with smaller pores like those found in clay. Because clay particles are small, they pack more tightly together and have more surface area per volume. Soils heavy in clay content have better structure than sandy soils but can be prone to water logging and tend to harbor higher populations of phylloxera.

As a result of their lesser water content, sandy soils warm up faster than clay soils, which initiates budbreak sooner and accelerates ripening. In a cool or wet vintage, sandier soils may perform better, while in a warm and dry year, soils with a higher clay content may be preferred. Parasitic nematodes are particularly fond of sandy soils.

Loam soils are considered ideal for vineyards, since the combination of particle sizes achieves the ideal balance of drainage, provided by the sand, and fertility, provided by clay, that is desirable for balanced vine growth.

Chemical Properties

While wine style is clearly influenced by the physical factors that dictate water availability, except in the case of nutrient deficiencies, few differences in wine can be attributed to a soil’s chemical composition. 

Rocks are made of minerals like quartz, mica, feldspar, gypsum, calcite, and flint. These minerals do not make their way into the glass directly; rather, the vine roots take up only small ions, including the 17 mineral nutrients that are described below. (Note that minerals and mineral nutrients are distinct from one another, though frequently confused.) While the weathering process releases a small amount of mineral nutrients from the soil, most of the nutrients supplied to the vine come from organic matter and fertilizers. Current understanding of rock chemistry suggests it does not play an important role in soil chemistry as related to the vine, with one important exception: calcareous soils are strongly alkaline. 

Soil pH

The pH of soil is its most important chemical property. pH is a scale of acidity that ranges from 0 (very acidic) to 14 (very basic), with water considered neutral at a pH of 7. Technically, pH is a measure of the hydrogen ions, or protons, dissolved in a solution, where more acidic substances have more protons. pH is a logarithmic scale, which means that a pH of 6 has 10 times the amount of protons as a pH of 7.

Soil pH ranges from 3 to 10. Soils described as acidic have a pH below 6.5, neutral soils are 6.5 to 8, and alkaline (basic) soils are over 8. From a viticultural perspective, neutral soils are considered ideal, while those lower than 5 are generally considered to be unsuitable for farming, though they may be amended to lift the pH to a more desirable range. Overly acidic soils might also induce aluminum toxicity, which is detrimental to root growth. 

High pH, above 8.5, is the result of significant lime content, which is found in calcareous soils including limestone, chalk, tufa, marlstone, and marble. These soils are frequently associated with wine quality, though the precise reasons for this connection are not well understood. Basalt, sandstone, shale, slate, and schist tend to be more acidic. The slate soils in the Mosel, for example, can have a pH below 6. Soil acidity, however, depends not only on the nature of the parent rock but also on climatic and human factors.

A soil’s pH influences the mineral nutrients that are available to the vine. Nutrients are stored by adsorbing, or sticking, to soil particles. Positively charged nutrients are attracted to soil particles, which are largely negatively charged. Soil particles have a limited surface area to hold nutrients, described as the cation exchange capacity (CEC). Larger particles like sand have less total surface area per volume and are less nutrient dense. Clay soils are rich in nutrients, but because the nutrients are bound more tightly, they are less available to the vine. Soil organic matter also increases CEC.

Nutrients compete for space on the CEC, so too much of one nutrient can induce a deficiency in another. In acidic soils, protons take up too much space on the CEC, and as a result, some nutrients are less available in low-pH soils. Acidic soil induces phosphate deficiency, while alkaline soils can induce iron deficiency. Along with soil texture, pH has a significant influence on the availability of nutrients. 

pH also influences which plants will grow. Most rootstocks are not well adapted to high pH, so lime-tolerant rootstocks, often Vitis berlandieri based, must be used. This is important to recognize, since it is difficult to separate the influence of rootstock from that of soil pH.

Agricultural soils become increasingly acidic over time, which can degrade soil structure and disrupt microbial communities. As nutrients are leached from the soil, protons take their place on the CEC. The decomposition of organic matter and respiration of roots release carbon dioxide, which forms carbonic acid in the soil. Additionally, the use of ammonia-based fertilizers increases acidity over time. A farmer may amend soil acidity through liming, which is the application of limestone, dolomite, or lime (calcium hydroxide), to neutralize the topsoil. Typically, this occurs when a vineyard site is being developed, but these materials can also be applied along with compost in an established vineyard to maintain a desired soil pH. Soil organic matter helps buffer against change in pH.

Soil Toxicities

Dissolved salts like sodium chloride (table salt) are toxic to plants in high concentration, as they hinder the vine’s ability to absorb water. Water follows a concentration gradient and flows from areas with less salt content to areas with more. Irrigating with water with a high salt content is one of the biggest causes of saline soils. Parts of California’s Central Coast, Mexico’s Baja region, and South and Western Australia struggle with salinity. In response, salt-tolerant rootstocks such as Ramey have been developed to adapt vines to saline conditions. Sodicity is a related concept but considers only the amount of sodium in the soil. Too much sodium reduces soil permeability and destroys soil structure because high concentrations of sodium have a repelling effect and disperse clay particles.

Vine Nutrition

Grapes have relatively low requirements for water and nutrients, as far as agricultural plants are concerned, so they may be cultivated on soils considered unsuitable for other crops. Yet deficiencies can limit growth and development. Soil fertility refers to the ability of the soil to provide nutrients. Starving vines for nutrients can reduce yields, impede the vine’s ability to ripen fruit, and render the vine more susceptible to pests and diseases. On the other hand, excess of certain nutrients can be detrimental to quality.

Vines require 17 essential nutrients for healthy function. Carbon, hydrogen, and oxygen are supplied by water and carbon dioxide from the atmosphere, but the rest are taken up through the soil. Of those absorbed through the soil, nitrogen, phosphorus, and potassium are by far the most important, as they are essential for plant growth and development. They are considered macronutrients, along with sulfur, calcium, and magnesium, as the vine uses them in macro quantities. Boron, manganese, copper, iron, zinc, molybdenum, nickel, and chlorine are micronutrients, as the vine has less demand for them.

Nitrogen has the most significant impact on grape quality and yields, and its availability is key to soil fertility. Insufficient nitrogen results in weak vines with short shoots and chlorotic leaves, while excess nitrogen can lead to vigorous vines with dark green canopies and reduced yields. Particularly for red grapes, the shade provided by this type of a canopy is considered negative for quality. Nitrogen-rich vines also attract pests such as leafhoppers. Plants are able to use nitrogen in the form of ammonia or nitrates. 

Potassium helps to maintains cell structure through osmotic pressure and facilitates ripening through sugar transport and deacidification. After veraison, potassium is exchanged for protons in the berries, lowering the fruit’s acidity. Potassium deficiencies can result in elevated levels of acidity in the fruit, low yields, and uneven ripening. Leaf discoloration and leaves that roll under are symptoms. Excesses can reduce fruit acidity and may induce deficiencies in other nutrients. Phosphorous is important for photosynthesis as well as energy storage and transport throughout the vine. It’s a key component of both nucleic acids and ATP. Deficiencies are relatively rare but reduce yields and cause discoloration of the leaf margin.

Nutrients are depleted from the vineyard over time as fruit and canes are removed at pruning. Certain nutrients, like nitrogen, are leachable, meaning they can be washed from the soil in groundwater runoff, while others, like phosphorus, are more immobile. Most vineyards require nutrient additions from time to time, particularly of the macronutrients nitrogen, phosphorus, and potassium (known collectively as NPK).

Producers can assess nutritional deficits through petiole sampling at flowering or veraison, taking soil samples, or observing visual symptoms. Nutrient imbalances like nitrogen and iron deficiency cause characteristic chlorosis, or yellowing of the leaves either along the leaf veins or within the leaf margin. With red grape varieties, imbalances like phosphorous and potassium deficiency may also cause reddening in the leaves due to an accumulation of anthocyanin, the same pigment that gives red grapes their color. These symptoms are easily mistaken for common diseases such as leafroll and fanleaf viruses.

Certain nutrients are mobile in the plant, and in the case of deficiency, they will be translocated from older leaves into newer ones, since the plant prioritizes the development of young leaves. Other nutrients are tied up in compounds that cannot move freely within the vine and are considered immobile. This can help with diagnosis of problems: if a nutrient is mobile, older basal leaves will show symptoms first. With immobile deficiencies, symptoms appear in younger leaves first.

Vineyard Establishment

Site Selection

Farmers have always sought the sites that produce the best wines. The phrase Bacchus amat colles, meaning “Bacchus loves the hills,” is an enduring observation from early explorations of site selection. While this process is more of an art than a science, some forethought can improve quality and save money. 

Within a region, certain sites are preferred based on their mesoclimates, the availability of water, and the rarity of adverse conditions like frost. Some sites ripen earlier than others, which may be advantageous in a cool region and less desirable in a warm one. Terrain is also a consideration. While hillside sites may be enticing, they are often more difficult and expensive to farm. Economic factors like the reputation and cost of the land and the proximity to markets, labor, and resources are considered as well. Because of the proliferation of vineyards in the past few decades, wine regions may have laws dictating if and where new vineyard land may be planted. While much of the vineyard land in Europe is already delineated, as viticulture spreads, the suitability of new sites may be evaluated by comparing their soils and climates to those of established regions.

Planting Material

In some regions, grape variety is dictated by local laws. Otherwise, the climate and intended wine style should guide the choice of varieties. Selection may also be influenced by factors such as personal preference, marketability, or tradition. Rootstock, where used, should be matched to the site conditions and any hazards to be mitigated, such as nematodes and high concentrations of salt or lime.

The influence of clone is generally small compared with site, variety, and rootstock. If multiple clones are available, flavor and yield considerations, ripening characteristics, disease resistance, and notoriety may guide the selection. In particular, several clones of Pinot Noir have been popularized for various flavor and ripening characteristics, including Pommard, Wädenswil, 667, 777, and 115. 

The vast majority of grapevines are grown from grafted vines with plant material obtained from a nursery. Grapevine propagation is labor intensive, and many growers are not equipped for this undertaking. Nurseries strive to provide vines that are virus free, an important assurance for a long-term investment. The downside is that nurseries are often limited in the varieties and clones that they carry.

Grapevine Propagation

Except under experimental conditions, wine grapes are almost never propagated from seed. During fertilization, DNA is recombined, so each seed produces an entirely new variety that may not possess the attributes of its parent plant. The seeds of self-pollinating vines are highly inbred and prone to recessive-type diseases; many are nonviable or non-fruiting. While they may share some similarities with their parent, vines grown from seed bear unique genetics, and it can take years to characterize a new vine’s behavior.

Instead, vines are propagated vegetatively from dormant cuttings, which are 12- to 18-inch pieces of cane taken from a parent plant. Cuttings are taken from dormant vines during the winter months and stored at low temperature until they are ready for use. Dormant cuttings of rootstock or vinifera varieties can be planted directly in the ground, or they may be grafted prior to planting. Ungrafted vines, typically rootstock selections, are sold as dormant rooted cuttings that have been grown in a nursery for a season, unearthed during dormancy, and kept in cold storage prior to planting.

Cuttings may originate from a single parent vine, called a clone, or from massal selection, where cuttings are taken from numerous vines throughout a vineyard that may have undergone small mutations. Producers who prefer clones hope to replicate the characteristics of the parent in their own vineyards. Since clones are genetically identical, they may result in a more even, easy-to-manage vineyard. A producer may instead choose massal selection for the increased genetic diversity, which could confer more disease resistance and, potentially, complexity in the wines.

Grafting is essentially the fusing of plant tissues of two different species. In the case of grapevines, grafting is typically used to join a vinifera scion to a non-vinifera rootstock. Occasionally, the variety may be changed in an existing vineyard by grafting onto established vines in the field, known as top grafting. In certain situations, this may be preferable to replanting the vineyard.

During grafting, cuts are made in both pieces of wood, allowing the vines to fit together and join like puzzle pieces. Two compatible plants with similar circumferences are connected such that their cambium, the layer of cells between the xylem and phloem responsible for wood’s increase in diameter, is matched up. Once the graft heals, the grafted vine functions as a single plant with characteristics from both the rootstock and scion. Traditionally, a number of different shapes of cuts have been used, such as a v-shaped cleft graft or an omega punch.

There are two major types of grafting in viticulture, bench and field grafting. In bench grafting, two dormant cuttings, the rootstock and scion, are joined together at the nursery, usually by machine. The scion cutting is trimmed to a few inches prior to grafting, leaving a single bud. Afterward, the graft is wrapped to provide support and stored in a warm, damp room for several months to “callus,” or heal. The graft union is then waxed, and vines are stored at cold temperature prior to planting in the spring. Grafted vines may be grown for one season in the nursery and sold as dormant bench grafts. Alternatively, the grafted cutting may be planted in a pot just after callusing, grown in a greenhouse, and sold during the same year as a green-growing bench graft, or potted vine. Potted vines are less expensive, and they mature one year earlier than dormant bench grafts. 

In field grafting, rootstock is planted in the vineyard in the spring and allowed to grow for an entire season. The scion is then grafted on top, either in the fall or following spring. Field grafting uses a technique called chip-budding, where very small pieces of cuttings containing a single bud are inserted into the rootstock. Similar to own-rooted vines, rootstock is sold as a dormant rooted cutting.

Of these options, bench grafting is easier and less expensive, and only vines that have been successfully grafted are planted. Field grafting is more expensive overall, yet the costs are spread out over two intervals. It requires skilled labor and can have a greater failure rate, but these vines have a more stable root system at the time of grafting and may have more longevity.

The choice of planting material is often inhibited by what is available locally. In the past, winemakers traveled to established growing regions and brought cuttings home with them to be used in vineyard establishment. While this practice allowed for diversification in newer growing regions, it is technically illegal in most countries and has been responsible for the proliferation of grapevine viruses all over the world. In order to import vines legally, a state-approved nursery must verify that the plant stock is pest and virus free, a process that takes several years but avoids undesirable stowaways. Foundation Plant Services (FPS) is the major US nursery used for this purpose.

Land Preparation

Prior to planting, land that has been used for vineyards or other agriculture in the past may be allowed to lay fallow (bare) for a couple of years or be planted with cover crops that build soil organic matter and nutrition. Soil assessments reveal a soil’s pH and any nutrient deficiencies, which are easiest to amend before planting. The land is cleared of trees, foliage, and large rocks and roots. Drainage may be improved through ripping or through the installation of subterranean drains to prevent waterlogging in low-lying spots. Earthwork is done in the spring or fall, when soils are damp but not too wet to pass equipment.

Determining a vineyard’s boundaries is one of the first steps of planning. Vineyards are typically divided into several management blocks, and thoughtful placement of the divisions between them simplifies vineyard management. Ideally, blocks are relatively homogenous in terms of variety, rootstock, soil, microclimate, and elevation. Boundaries often respect natural borders formed by topographical features, transitions in soil, and roads. A grower may choose to adapt varieties, rootstock, and vineyard architecture to the block’s natural characteristics.

Vineyard Architecture

A vineyard’s layout and trellis system design are referred to as its vineyard architecture. Row orientation, or the rows’ planting direction, is a fundamental decision. A north-south orientation allows both sides of the vine an equivalent duration of sunlight throughout the day. The downside is that fruit on the west side of the vine may be overexposed to the afternoon heat. East-west rows allow the canopy to intercept the maximum amount of sunlight all day, but this will result in significant differences between the north and south side of the vine, as the south side has more exposure. Recently, northeast-southwest orientations have become popular in warmer regions, as they maximize light interception while also shading themselves during the hottest part of the day, protecting fruit from sunburn and dehydration. 

On slopes, rows may either be oriented up and down or across the slope. Rows that follow the slope have better airflow and are generally safer for equipment, provided that rows are not too steep. However, this orientation can result in erosion, and fruit along the row may be uneven due to differences in elevation. On steep slopes, terracing is necessary for rows planted across the slope to allow equipment to work safely. Classic examples of terracing are found in Portugal’s Douro, the Northern Rhône, and Alto Adige. Terraced vineyards are expensive to build and maintain and can be difficult to manage. They also have a tendency to create heterogeneous soils due to the large amount of earth that must be moved to create the terraces.

Vineyard spacing refers to the distance between rows as well as the distance between vines. The combination of these is called vine density, which typically ranges from 500 to 6,000 vines per acre, while the space between vines and rows typically ranges from about 4 feet to 12 feet. European vineyards tend to use higher density, with 4,000 vines per acre (10,000 vines per hectare) being common. Much of the New World uses planting densities of 1,500 vines per acre or less.

Narrow row spacing is more efficient in terms of land use but may require specialized tractors and farming equipment. High-density planting is used to limit vine vigor through competition and to maximize yields, and it is believed by some to produce higher-quality fruit. Vigorous vines, however, are better suited to wider spacing. Low-density planting may also be more appropriate for vineyards with inadequate water supply or for dry-farming, as observed in many Spanish wine regions. It can significantly reduce farming costs since less infrastructure is required and there are fewer vines to tend to per area. Efficient vineyards do not leave empty space along a vineyard row, so if wider vine spacing is used, the size of the vine is generally adjusted to fill all of the available room.

Trends in vineyard architecture are subject to the prevailing wisdom of the time. Producers often look to classic regions that they admire or to their neighbors to inform their choices. However, what works on one site, or in one region, may not be the most appropriate layout for all sites.

Planting

Planting occurs over one or two years, and once vines are in the ground, the vine requires at least two or three years to become established before any fruit is harvested. During the first year after planting, the focus is on growing healthy roots. In the next couple of years, it shifts to development of the vines’ permanent structure through vine training.

Vines are planted by hand or machine. While hand-planting is traditional, it is labor intensive. Machine planting is significantly less expensive and can have very good results; it shows a lot of promise as an opportunity for mechanization. Planting typically occurs in the spring, though vines may be planted anytime during the growing season, taking care to avoid frost before the vine has become established.

Young vines require more attention than those that are established. J-rooting, a common cause of young vine decline, occurs when vines are placed in holes with their roots bent upward. Young vines are also prone to certain fungal diseases that can result in vineyard failure if infected plant material is used. While the notion of starving vines of water to encourage deep root growth has been popularized, young vines’ root systems are not well developed, and they may require frequent irrigation. Water stress will stunt growth and ultimately shorten the life of the vine. Even in regions where irrigation is not permitted, exceptions are typically made for vineyards less than three years old. 

Growers remove weeds that can outcompete or girdle young vines and often place growing tubes around the vines to protect them from weeds and animals. During the first two to three years, any fruit that forms is typically removed to allow the vine to put maximum energy into vegetative growth. Failing to do this can weaken vines and shorten the vineyard’s lifespan. 

Vine Training

A vine’s training system is the shape and position of its permanent structures, including the trunk, cordons, canes, and spurs, and is best observed after winter pruning. The training system is ultimately determined by the cuts made during pruning in the first few years, which have a long-term impact on the vine’s shape.

The three most common vine-training systems are cordon-trained and spur-pruned; head-trained and cane-pruned; and head-trained and spur-pruned. Considerations for choosing the most appropriate system include grape variety, environmental conditions, and yield goals. Very often, tradition, which may be codified in law or local trends, will also play a role.

Cordon-Trained & Spur-Pruned

Cordon-trained, spur-pruned vines, commonly referred to simply as cordon-trained vines, can have up to four cordons attached to the trunk, described as unilateral, bilateral, or quadrilateral. Along each cordon are permanent spur positions located every few inches. As the grapevine ages, permanent wood accumulates at the base of each spur and develops into arms. Shoots grow from the spurs during the season, and during pruning they are trimmed back into spurs, so that each year, the vine looks nearly identical.

There are a number of advantages to this system, which has been widely adopted, especially in warmer regions. After establishment, cordon-trained vines are the easiest, fastest, and cheapest to prune. Shoot development along the cordon is generally very even, with a clear fruit zone. This system is also suitable for mechanization. Because these vines have more permanent wood than other systems, they store more water and nutrients and may better tolerate adverse environmental conditions. 

However, cordon-training is not always the best option. An extra year may be required before fruit is harvested to establish the cordon and spur positions. Cordon-trained vines store more reserves through the winter since they have more permanent wood, resulting in more vigor and a need for wider spacing. Spur-pruning is not appropriate for varieties that have low fertility in buds close to the cordon, such as Nebbiolo and Carmenère, since spur-pruning can reduce their yields. It is also risky on frost-prone sites. In these conditions, all buds tend to push at the same time, opening up the vine to greater loss. To minimize this risk, some growers pre-prune the vines or leave kicker canes, strategies that help minimize frost risk.

Head-Trained & Cane-Pruned

Head-trained, cane-pruned vines typically have one or two canes (though as many as four are possible) attached to the head (top) of the trunk. Guyot is a well-known variation of cane-pruning that includes one spur for each fruiting cane attached directly to the head, called replacement or renewal spurs. During the growing season, shoots form on each bud along the cane and renewal spurs. The grower selects and lays down a new fruiting cane, called the baguette in French, during pruning each year, removing the cane from the previous season. Renewal spurs ensure that there is always a good supply of canes near the head of the vine that may be retained for the coming year.

The main advantage of cane-pruned vines is that they have less permanent wood and fewer reserves, so they are less vigorous and better suited to high-density plantings. Despite their lower vigor, they are often more productive than spur-pruned vines (when grown under equivalent conditions) and may require more fruit thinning to ensure adequate ripening. Cane-pruned vines have fewer pruning cuts than spur-pruned vines; as a result, they may be less prone to fungal diseases that enter the vine through pruning wounds. Many believe that cane-pruning is inherently better for wine quality. It is used in many of Europe’s most esteemed wine regions, so it has been adopted by many producers. 

Yet there are some important disadvantages of this system. Cane-pruned vines require skilled labor for pruning, which increases farming costs, and they are not suitable for mechanization. They are more susceptible to winter freeze, because buds are located further from permanent wood, leaving them more vulnerable to damage. Due to apical dominance, budbreak and development are uneven along the cane, with uppermost buds and those located at the vine’s extremities favored. 

Head-Trained & Spur-Pruned

Head-trained, spur-pruned vines—also called bush, gobelet, or head-trained vines—have many spur positions attached to arms that form from the head of the vine. During the growing season, shoots will form at each spur position, and at pruning, the spur positions will be restored. Head-trained vines are typically found in warm, sunny growing regions with limited water availability. Much of Spain and Southern France, and vineyards with older plantings in California, utilize this training system. Head-training systems are also common with large-bunched varieties that are prone to rot, like Zinfandel and Petite Sirah, since the lack of wires and stakes prevents the clusters from becoming tangled in the trellis and damaged as the fruit develops.

Head-trained vines are the least expensive to establish and manage, since no trellis system is required, and as a result, canopy work is minimal. The initial training and pruning of head-trained vines requires skilled labor, though pruning becomes easier over time. However, head-trained vines are the least productive and not suitable for mechanization. Because all of the fruiting shoots are attached to the vine near the head, this system is prone to crowding. Head-trained vines share the same concerns of frost risk, trunk disease, and low-bud fertility as cordon-trained and spur-pruned vines.

While a number of other training systems exist, most are a variation of these basic structures, which can be adapted by leaving additional cordons, canes, or spur positions. The novel Sylvoz training system, used on high-yielding varieties and sites, is cordon-trained and cane-pruned. This results in a large number of fruiting shoots during the growing season and is an example of adapting the training system to the site and yield requirements. Champagne employs a number of unique training systems, including Taille Chablis and Vallée de la Marne, that are high-yielding and reduce the risk of frost damage.

Trellis Systems

The organization of the vine’s canopy begins with the choice of the trellis system, or the structure of posts and wires that support the canopy. A vine’s trellis accommodates its natural impulse to grow vertically and provides support for the shoots and fruit, since the vine is not able to support itself. It helps spread the shoots out more evenly, which improves airflow and light penetration in the canopy, reducing disease pressure and increasing the photosynthetic capacity of the vine. From a practical standpoint, the trellis system facilitates vineyard operations. It keeps shoots out of the vineyard row, allowing tractors and other equipment to pass. Because the shoots are organized in a predictable pattern, canopy management work is easier.

The shape of the vine training system often guides the options for trellising. The trellis typically considers the natural growth patterns of the vine. Shoots can be trained upward or downward, or they may be partially supported by a wire and then allowed to drape down. Vitis vinifera likes to grow vertically and will be devigorated if it is trained downward, whereas hybrid grapes often prefer downward growth. Large vines require more space and a more extensive trellis system, such as a divided canopy system, which has multiple fruit zones and allows the vine to spread out.

Climate, soil, variety, and rootstock must all be considered when choosing a trellis system, which will influence the vine’s microclimate. Cooler climates require more efficient sunlight interception, while sunny climates demand protection. Humidity and airflow are also important considerations. Finally, there are practical factors like cost, ease of use, and compatibility for mechanization. Simpler systems with fewer wires are usually less expensive and less labor intensive. Mechanization works best on cordon-trained, spur-pruned vines with a single “wall” of shoots. 

While a number of trellis system designs exist, it is more important to understand the concepts behind them than each individual design. While some of these trellis systems are traditional, others were designed more recently to optimize microclimatic conditions. Variations of each of these are common around the world, and many similar systems go by different names.

Untrellised Vines

Head-trained vines are typically not trellised. In sunny climates, shoots may be left to drape onto the floor, while in cooler climates, shoots may be tied to a central post for support and to allow more sunlight in the canopy and fruit zone. Untrellised vines require very little canopy management, since minimal work is required to arrange shoots. Because shoots sit on the vineyard floor, some vineyard operations, like running equipment through the rows, are more challenging. This arrangement can result in dense canopies with excessive shading and increased disease pressure, which is exacerbated by the difficulty of getting adequate spray coverage. Untrellised vines are not suitable for mechanized harvesting.

Non-Divided Canopy Systems

Cordon and cane-pruned vines have many options for trellis systems. These are broadly categorized as divided or non-divided systems, and in each case, shoots may be trained upright, or they may be allowed to hang down toward the ground.

On low-vigor sites, cordon and cane vines are often trained to one or two horizontal canes or cordons, referred to as a non-divided system, since there is a single fruit zone. Several trellis systems are commonly used for non-divided canopies. In vertical shoot positioning (VSP), the shoots are trained vertically and compressed into a single wall between several wires of support. VSP is ideal for high-density plantings. It respects the tendency of vinifera grapes to grow vertically and results in good light interception. VSP works well for lower-vigor vines, as shoots may be positioned for good airflow and coverage with anti-fungal sprays. For vines with higher vigor, the canopy may become too dense and humid, restricting airflow and harboring disease. Warmer climates that risk overexposure may require more protection in the fruiting zone. VSP is suitable for mechanization; however, this system requires additional labor to tuck shoots into the trellis. It is moderately expensive to install and operate.

Where more protection from sunlight is desired—for example, on warmer sites that are prone to sunburn—a slightly wider variation of VSP may be used, with spreader bars that open the canopy slightly. This is also good for more vigorous vines, since it allows for better airflow and sunlight penetration into the canopy and reduces crowding in the fruit zone.

California Sprawl is an example of a two-wire system. In this layout, the shoots are flopped over a single higher wire that provides support and shade to the fruit zone. Two-wire systems are less expensive to install and require less canopy work than VSP. This system is compatible with vigorous canopies but may restrict airflow such that the underside of the canopy becomes humid and prone to disease. 

In high-wire systems, such as high bilateral cordon, the cordon or cane is trained along a support wire, while the fruiting shoots sprawl unsupported in all directions. It is a good low-cost option since it is well suited to mechanization and requires little canopy management, and with basic infrastructure, it is inexpensive to install. Because the fruit is located near the top of the vine, it gets good light exposure, but this system might not offer suitable protection in very warm climates. High wire systems require a tall head height, so these vines can be difficult to prune and harvest by hand. 

Divided Canopy Systems

On high-vigor sites, a divided canopy may be utilized to provide more space for the vine and avoid overcrowding. Divided canopy systems are typically quadrilateral cane or cordon-trained. The canopy may be divided horizontally, with two parallel fruit zones located three to four feet apart at identical heights, or vertically, with an upper and lower fruit zone. Many of these have an analogous non-divided canopy system. Uneven ripening is a risk of divided canopies since there are multiple fruit zones. Some producers will even harvest the different zones on different dates.

There are horizontally divided equivalents of each of the systems mentioned above. Lyre is similar to VSP, Wye is similar to California Sprawl, and Geneva Double Curtain is similar to the high-wire system. In each case, the canopy is mirror-imaged across the vine row.

Scott Henry and Smart-Dyson are unique vertically divided systems used primarily in New World wine regions including parts of New Zealand, Australia, Argentina, Chile, and the United States, as well as Spain and Portugal. Scott Henry is a quadrilateral cane-pruned system, with two canes trellised vertically and two trellised downward. This system is used for high-vigor situations where tighter row spacing is desired. While efficient, the fruit from the upper and lower fruiting zones will ripen at different times (fruit on the upper cane ripens first, another example of apical dominance). Smart-Dyson is a similar system used for high-vigor bilateral cordon vines, where shoots are trained both up and down. It is very suitable for mechanization, and the fruit on these vines ripens more evenly than with Scott Henry. Overly vigorous VSP vines can easily be retrofitted to this system. 

Other novel trellis systems are possible. Pergola, also called tendone in Italy and latada in Spain, is a classic system used on high-vigor, high-production vines in Southern Europe. Pergola systems allow workers to pass below the vines. These systems make efficient use of vineyard space, allowing maximum light interception by the canopy while also providing adequate protection in the fruiting zone. In humid areas like Rías Baixas, pergola trellising promotes airflow and reduces fungal disease pressure. Whereas the canopy of other trellis systems can be thought of as perpendicular to the ground, in pergola systems, the canopy is parallel. The high height of the fruit zone makes pruning and harvesting challenging, and this layout doesn’t easily accommodate driving equipment through the vineyard.

A Year in the Vineyard

Phenology is a term that describes a vine’s reoccurring patterns of growth and development throughout the year. Major milestones include budbreak, flowering and fruit set, veraison, harvest, and leaf fall. Except in tropical environments, grapevines fruit once per year. They spend the entire growing season establishing a canopy and ripening their fruit, and during dormancy, they survive off of carbohydrate reserves stored in the trunk and roots during the growing season.

In the Northern Hemisphere, the growing season begins with budbreak (or budburst) in March or April and ends with harvest sometime between August and November. (In the Southern Hemisphere, budbreak occurs in September or October, with harvest between February and May.) While the dates of budburst, flowering, and veraison are reasonably consistent for most varieties, with differences of about two weeks at most, a much larger span of harvest dates is observed between varieties.

Start of the Growing Season 

When the temperature begins to warm to about 50 degrees Fahrenheit, the vine begins transporting sap containing nutrients and energy stores from the roots to the buds to initiate shoot growth. This may be observed as weeping, where sap is pushed through open pruning wounds. Excessively wet conditions at this time might prevent soils from warming, stifle root growth, and delay the start of the season.

At budbreak, the dormant buds begin to “push,” and the compressed shoots stored inside begin growing. The first leaves appear, and as the shoot elongates, new leaves emerge from the shoot tip. The growth is slow at first, fueled by energy stored in the roots and trunk. Budbreak occurs according to apical dominance, where buds that are located further from the ground push first. 

After a few weeks of slow growth, the vines enter a period known as rapid shoot growth or the “grand period of growth.” During this time, shoots may increase in length by inches per day. By flowering, the shoots are typically about half of their full size. 

Flowering & Fruit Set 

Grape flowers do not resemble the common notion of a flower with petals radiating from the pistil (female flower part). Rather, grape flower petals form a cap around each flower that falls off during flowering to reveal the stamens (male flower parts). Pollen from the stamens falls onto the pistil during fertilization, and each fertilized flower turns into a grape berry. The weather during flowering is critical, as low temperatures interfere with fertilization, ultimately reducing the number of berries as well as the overall yield. Bloom typically begins six to eight weeks after budbreak and continues over a span of one to three weeks.

Shortly after flowering, during fruit set, fertilized flowers turn into berries and the yields for the season become more apparent. Under favorable conditions, roughly a third of flowers develop successfully into berries. Flowers that are not fertilized fall off.

The rapid growth phase pauses during flowering and resumes after fruit set. After set, the vine begins devoting more energy to fruit development. The berries are hard and green at first and rapidly increase in size as cells within the berries divide. Starting at set, reactions begin taking place inside the berries that will ultimately determine berry composition, and the environmental conditions around the cluster more significantly influence fruit composition. Acid, tannin, and some flavor precursors begin accumulating, and the timing of canopy management operations becomes more critical.

Veraison

Veraison is one of the most recognizable and photogenic phases of grape development, where grapes change color from green to red—or, in the case of white grapes, from bright lime green to a pale, translucent green. This occurs about four to six weeks after flowering and marks many important changes in the vine. Prior to veraison, the vine invests its energy into growth and development. By veraison, the shoots are typically full height, and the vine’s energy is focused on fruit ripening. Color, flavor, and sugar begin accumulating in the fruit. Acidity and astringency decrease, and the fruit begins to soften. Berries continue increasing in size for several weeks after veraison, but cell enlargement, rather than cell division, is responsible for this increase.

Harvest & Post-Harvest

Depending on the desired level of ripeness, harvest ranges from 4 to 12 weeks after veraison for dry wine styles. Harvest for sweet wine styles may occur much later in the fall. Different varieties ripen at different rates, and ultimately, the winemaker decides when the fruit is ready to be harvested. Ripeness should be thought of as a spectrum, rather than a discrete point, and harvest timing within this ripening window has serious implications on wine style and expression of site.

After the fruit has been harvested, the canopy changes colors from green to yellow as leaves senesce. The vine redistributes energy from the canopy into the trunk and roots. During this time, the vine must store enough energy to provide for early development in the following year, from budbreak until leaves are big enough for photosynthesis. After nutrients have been translocated from leaves and shoots into the permanent features of the vine, the end of the season is marked by leaf fall, when spent leaves fall and the vine enters dormancy.

Vineyard Operations

Pruning

One of the most important annual operations in the vineyard is pruning, where last year’s vegetative growth is removed to make way for new growth during the coming season. During pruning, viticulturists determine the number and position of buds that will turn into shoots. Through the process, they set potential yields, guide the permanent shape and balance of the vine, and foster organization to facilitate other operations. Pruning is not only one of the most technical vineyard operations, since the decisions made affect the vineyard’s long-term trajectory, but also among the most expensive and labor intensive. Its goal is to slowly work toward vine balance.

Pruning diminishes the overall capacity of the vine by leaving fewer shoots and leaves to support fruit ripening. It concentrates the vine’s energy into the buds that remain, so that the shoots they produce are longer, stronger, and more fruitful. If a vine is pruned with balance in mind, yields will stabilize over time, since the vine is neither overtaxed nor overshaded, both of which decrease yields.

There are a few conventional wisdoms used during pruning:

• The most fruitful buds are those on one-year-old wood (from last year’s fruiting shoots).
• Thicker canes should be pruned to longer spurs with more buds since they have more capacity than smaller canes.
• If there was excessive vegetative growth in the previous year (for example, if shoots grew too long), more buds should be left this year to balance the shoot growth.

Pruning occurs during winter dormancy and before budbreak. In the Northern Hemisphere, this is typically between December and March. Vines that are pruned earlier in this window may be more prone to fungal trunk diseases and winter freeze. Pruning should never be done in the rain, and it is ideal to wait several days after the last rain to minimize the risk of fungal disease. Late pruning can be used to delay budbreak slightly in order to avoid the risk of spring frost, but if it occurs after budbreak, it can ultimately weaken vines. Ideally, pruning should occur as late as possible, while still being finished in time for the start of the season, but timing is often dictated by the availability of labor. 

Spur Pruning 

A spur with two buds will grow into two shoots during the season. At pruning, one of these shoots is removed entirely, while the other is trimmed back to a spur. The only decision the pruner must make is which cane to use for the spur. For spurs on cordons, the lower cane is typically favored to keep spur positions from reaching too high. It is also best for the spur to be vertical, which may override this preference for the lower cane.

Spur-pruned vines may be pre-pruned, where the top portion of the cane is cut and removed from the vineyard prior to making the final pruning cuts. This is a method used to divide labor, allowing the second pruning pass to occur as late as possible. The first pass is more labor intensive, since the brush must be removed from the trellis, whereas the second pass is more thoughtful, since these are the pruning cuts that matter.

Head-trained vines require a longer-term vision, considering where the shoots will grow the following year. Typically, spurs that are oriented away from the head of the vine are most desirable. During establishment, spur positions will occasionally be pruned into “rabbit ears,” where both canes at a spur position are pruned into spurs for the following year, to leave more buds and increase the capacity of the vine. 

Cane Pruning 

In cane pruning, buds that grow into fruiting shoots come from a single cane instead of many spurs. Pruning cane-pruned vines is more complex. Guyot is a specific type of cane pruning, where the producer selects one cane that will be retained and used as the fruiting cane the following year, and one cane that will be trimmed into a renewal spur. The renewal spur may be the next year’s fruiting cane, so its placement is critical. Renewal spurs should be located close to the head of the vine, and the spur should be oriented such that it is not growing into the row.

Selecting a suitable cane is also important. An ideal cane is moderate in diameter, with normally spaced internodes, and is well positioned so that it may be bent and tied to the support wire along the vineyard row. Canes are generally pruned to between 8 and 16 nodes. The number of buds retained depends on the growth observed in the previous season along with yield goals for the season ahead. After a suitable cane is selected, the rest of last year’s growth is removed.

In cane pruning, the cane must be tied to a trellis wire for support. This is generally done as a second pass that happens once pruning is finished. For varieties where buds in the middle of the canes may struggle to push, the cane may be tied into an arch to encourage more even growth. This training technique, sometimes called “cane cracking,” is often used for Riesling in Germany and Nebbiolo in Piedmont.

Mechanical Pruning 

Pruning for cordon-trained, spur-pruned vines may be done mechanically, using a method similar to hedging. Common mechanical pruners cut everything off of the vine above a certain height, or make cuts around four sides of the cordon, called box-pruning. Mechanical pruning leaves long spurs and results in haphazard canopies. While effective, mechanical pruning cannot replicate the quality of pruning by hand, which benefits from human intuition and thoughtful decision-making. Mechanical pruning is unlikely to gain widespread acceptance any time soon, but it is more widely used for pre-pruning.

Minimal pruning, where vines are pruned minimally or not at all, is used occasionally in grape production, more often for raisins. While this is not a technique that will be adopted by many wine producers, it does provide an interesting illustration of how the vine regulates itself over time. Minimally pruned vines have many short shoots, and while clusters are irregular in size and position, they tend to orient themselves on the outside of the canopy. These vines develop an extensive system of permanent wood and do not resemble the organized, homogenous, well-position vines of many vineyards.

Canopy Management 

While a region’s macro- and mesoclimates shape vine growth and development, the vine’s microclimate is largely determined by its canopy. The main function of the canopy is to provide energy to the vine through photosynthesis. A vine’s photosynthetic capacity increases with the amount of sun-exposed leaves. Additionally, the canopy hydrates and cools the microclimate through transpiration and evaporative cooling. Dense canopies are more prone to fungal disease, as they are more humid but also have less airflow, and they make it more difficult to get coverage from sprays that protect the vine from mildew and botrytis.

Canopy management includes a series of vineyard tasks designed to fine-tune the microclimate and organize the vine. It is one of the most effective ways for a producer to improve wine quality, especially in vigorous or disease-prone vineyards. The importance of sunlight in the canopy and fruit zone were more fully realized in the last 40 years, and since then, more extensive research has informed the practices used today.

Appropriate canopy management practices depend on the conditions of the growing environment as well as vine vigor. Warm, sunny climates often demand more protection from sunburn and dehydration, while cool, wet climates require maximizing sun exposure and reducing disease pressure. More work is needed to keep vigorous vines healthy and their quality high. Labor availability is also an important consideration, as many of these operations occur during the spring and early summer, often the busiest part of the growing season. Fruit cost will help dictate the extent of canopy management that is reasonable. 

During shoot thinning, unwanted shoots are removed to reduce crowding and competition. Good candidates for removal include multiple shoots growing from a single bud, suckers, laterals, and shoots that are growing in inconvenient spaces, such as into the vineyard row. Vigorous vines will push more suckers and laterals and require more shoot thinning. Timing is important. It’s easiest to remove shoots before they are six to eight inches long, but removing unwanted shoots too early encourages more to grow in their place. A viticulturist may prefer to let the shoots grow longer to diffuse energy. If vigor is limited, thinning should be done sooner to allow the vine to focus its energy on remaining shoots. The process often begins prior to bloom and may be repeated as necessary.

Through shoot positioning, a viticulturist orients the shoots in the canopy in an organized and even way. Where a trellis system is used, positioning also involves tucking shoots into support wires that help hold the shoots in place. Shoot positioning creates an even environment, with a balance of light exposure and protection, and makes all subsequent vineyard work easier. It’s done after bloom, once the shoots are long enough but while they are still sufficiently flexible to bend without breaking and are not too tangled.

Leafing, or removing leaves from dense canopies, improves airflow and sunlight penetration throughout the canopy and fruiting zone, which reduces disease pressure. Often, leaves are removed from the morning side of the canopy in the fruiting zone but retained on the afternoon sun side. Internal leaves may be removed from higher up in the canopy to increase airflow and light while leaving fruit protected. Leafing can be done any time after fruit set, but earlier is better. Exposing shaded berries to sun later in the season makes them more vulnerable to sunburn, since they aren’t well adapted. The maximum benefits of sunlight in terms of flavor development occur prior to veraison.

Suckering and leafing can be mechanized. While this might slightly damage the remaining shoots, it allows for timely action, which may ultimately be more important in terms of fruit quality.

Hedging is trimming shoots and leaves that fall outside of the plane of the canopy. It creates a tailored, shrub-like appearance. Hedging keeps the rows clear and prevents damage from vineyard equipment. Topping is a specific form of hedging where shoots are cut at the top to keep them from growing taller, as they will continue to grow as long as they have enough water, since they lack a terminal bud. Topping is done after shoots have reached their maximum height, if the growing tip is still green and active.

Along with pruning, cluster thinning is an opportunity for the viticulturist to manage yields directly. Clusters may be removed to achieve targeted yields and prevent overcropping. Young vines are often prone to setting too much fruit for their small stature, and there are varieties, including Chenin Blanc, Carignan, Grenache, and Valdigué, that are more ambitious in terms of yields. As vines move toward balance, they require less crop adjustment.

Cluster thinning may be done at any time throughout the growing season but generally occurs between fruit set and veraison, once yields can be estimated. A common technique is to leave two clusters on healthy shoots, one cluster on shoots that are half-height, and no fruit on short shoots. On low-vigor and cooler sites, it might be more prudent to leave only one cluster per shoot. A second round of cluster thinning known as green drop, or green harvest, may be done at the end of veraison, where clusters with delayed maturity are removed to promote homogenous ripening. To hasten development and not overtax the vine, however, earlier crop removal is better.

In many vineyards, the economics of dropping fruit do not make sense, as the grower is literally leaving money on the ground. While lower yields do not necessarily result in higher quality, the grower may be incentivized to retain more fruit than is ideal. For this reason, some producers have moved toward acreage contracts, where a buyer pays for fruit by the acre instead of by the ton. Ultimately, many wineries seek to own vineyards in order to tailor viticultural practices to the needs of their wine program.

Vineyard Floor Management

For part of the year, native grass and broadleaf species, weeds, and cover crops grow on the vineyard floor. These plants will impact the amount of water and nutrients available to the vine and, as a result, managing the vineyard floor is an important aspect of managing the vine. The conditions on the vineyard floor also influence the microclimate. Bare soil is warmer than soil covered in plants. Covered soils are cooler during the day but may take longer to cool off during the night, since airflow is impeded. These soils are also more prone to frost damage on emerging shoots, as pockets of cold air can become trapped in tall cover crops.

Cover crops are intentionally seeded during the fall. Legumes like peas and clovers and a range of grasses are common in viticulture. Legumes add nitrogen to the soil but have low water requirements. Some grasses have high water requirements and can be used to devigorate vines through competition. Brassicas may help control nematode populations. Cover crops and other plants limit erosion during the winter months, reduce compaction, and soak up excess soil moisture in the spring. During the growing season, plants compete with vines for water and nutrients. Later in the season, they may wither and die, or they may continue to grow if there is sufficient water.

The primary goals of vineyard floor management include optimizing the amount of water and nutrients that are available to the vine, limiting erosion, building soil organic matter, and influencing microclimate. Good cover crop selection coupled with appropriate vineyard floor management strategy will also keep invasive weed species from inundating the vineyard. On the practical side, clearing the vineyard floor allows workers and equipment to pass easily and safely through the vineyard rows, and keeps weeds from becoming entangled in the vines.

During the growing season, a number of practices are used to manage plants on the vineyard floor. From a practical standpoint, the work is divided into two zones that are managed using different machinery. While the alleyway between rows is easy to access with tractors and plows, the area under the vine row requires more specialized equipment.

Mowing is generally the first step of control against weeds and cover crops. Just after budbreak, rows may be mowed to increase airflow and reduce frost risk. Mowing early in the season encourages regrowth and can be used to soak up excess moisture. In dry climates, mowing later in the season will typically kill the groundcover. Tillage, or cultivation, is the turning over of the top 6 to 10 inches of soil. Tillage can be used to add fertility to the soil through green manure and reduces competition between the vine and groundcover for water and nutrients. It also reduces rodent populations, which can cause significant damage on no-till soils. Tillage is not typically practiced on hills, as it encourages erosion. Some producers vehemently oppose tillage since it destroys soil structure, can hinder water’s absorption into the soil, encourages erosion, and disrupts soil microbial communities. As soil is turned, carbon is brought to the surface and off-gases as carbon dioxide, which some believe contributes to global warming.

Mulching, also called green mulching, refers to mowing or crimping cover crops and grasses so that they make a carpet over the vineyard that discourages weeds from growing. Crimping uses a heavy implement to flatten plants to the ground, making “crimps” every few feet that damage the plants. Mulching helps conserve soil moisture and also reduces the soil temperature, which some believe is beneficial for soil bacteria. When compared with bare soil, it cools the microclimate, since the ground stays at a lower temperature and does not reflect much sunlight back into the vine. 

Under the vine row, herbicides are the cheapest and easiest method for weed removal, but many are critical of their use in farming. While organic herbicides exist, they are not particularly effective. Producers are increasingly moving away from the use of herbicides in favor of mechanical cultivation, which involves using a French plow or other implement that scrapes the top of the soil to remove weeds and other plants. Others plant a low-growing perennial cover crop like clover that will outcompete the weeds.

Most of these practices occur in the spring and early summer, once the soil is dry enough for equipment to enter the vineyard without becoming stuck. Timing depends on water and nutrient availability and how much competition is desired, as well as labor, since this is a busy season in the vineyard. In dry climates, competition for water should be limited, so cover crops may be mowed, crimped, or tilled early in the season. In wet climates, cover crops can be used to remove excess moisture from the soil and may be allowed to grow year round. 

Beyond these factors, there are different schools of thought in terms of management techniques. On one end of the spectrum, some farmers will cultivate the soil each year in the spring, once soils are suitably dry, to integrate cover crops and weeds and remove sources of competition and habitat that might harbor pests and rodents. Weeds underneath the row may be cultivated using an implement like a French plow or desiccated using an herbicide like glyphosate. These techniques can reduce irrigation requirements and are popular with those who dry-farm. Others see the plants that grow on the vineyard floor as a vital part of the vine’s ecosystem and put a great deal of thought into what is growing there, when it is growing, and how to manage it. They view cover crops less as competition and more as an opportunity for building soil fertility and organic matter. Nitrogen-fixing cover crops may be selected to add nitrogen to the soil. Where competition needs to be limited, cover crops with low water requirements or those that go to seed early in the season may be planted. These producers typically prefer practices that maintain soil structure, using, for example, mowing and crimping rather than tillage.

Water Management

Water management is another lever for influencing grape quality. Ideally, the vine has enough water to keep it functioning healthily, but not so much as to induce additional vegetative growth. In many climates, the soil has plenty of water early in the spring, though excess moisture in the ground at this time can cause waterlogging, which inhibits root growth. Springtime rains, if paired with ample sunshine, can produce vigorous vegetative growth early in the season, but by mid-summer, water may be in short supply.

Throughout the growing season, precipitation or irrigation is generally necessary for vineyard health. Irrigation is expensive and labor intensive, and most producers prefer to avoid it, if possible. Unfortunately, not all wine regions and sites are suitable for dry-farming. Historically, vineyard sites with adequate water reserves were selected, but as the climate changes, dry-farming is becoming increasingly difficult even in some traditional growing regions. The upside is that where water is limited, it can be controlled, which can be beneficial since excess water is often the culprit for low wine quality.

In areas where irrigation is not used, water management occurs passively through site selection, decisions made during site preparation, and vineyard floor management. The resulting wines may demonstrate more seasonal variation, and for this reason, it could be argued that they present a more honest expression of the vintage. On the other hand, where irrigation is used, the viticulturist can fine-tune the vine’s water status.

While more generous irrigation can be used to help support a larger crop load, quality-minded producers typically follow a deficit irrigation strategy. Where deficit irrigation is used, vines often receive less water during the growing season than they would in a region with regular summer rainfall. Under deficit irrigation, the vineyard is monitored for water stress, and just enough water is added to keep the vine healthy. Some growers irrigate fewer times at larger volumes, while other irrigate more frequently at lower volumes. The former technique is used to encourage deeper root growth and to acclimatize the vine to water stress. The latter may be more appropriate on soils with low water-holding capacity. Partial rootzone drying is a specific deficit irrigation technique where only half of the rootzone receives water at a time, which encourages the vine to be more efficient with its overall water use throughout the season.

Growers who irrigate monitor water stress in a number of ways:

• NDVIs are vineyard maps that demonstrate vine vigor, based on the color of the canopy, as captured by aerial infrared photography. These maps suggest areas of water stress.
• Soil moisture probes give an indication of the amount of water in the soil.
• Leaf water potential is a measurement taken using a tool called a pressure bomb on individual leaves, identifying their degree of water stress. The amount of pressure that must be applied to a leaf in order for it to release water from the petiole (leaf stem) indicates how many stomates are closed, a response to stress conditions.
• Predictive models estimate how much total water is lost from the vineyard soil through evapotranspiration (the combination of water lost due to evaporation from the soil and transpiration from plants) and then add back a certain percentage of this amount, depending on the weather forecast.

Though irrigation has been used in agriculture for about 8,000 years, a number of different types of irrigation are practiced today. Drip irrigation is by far the most common. It is highly efficient in its water use but expensive to install and maintain. It also provides the ability to fertigate, where fertilizer is added through the irrigation system. Overhead sprinklers are another option, applying water evenly over the surface of the vineyard. Sprinklers double as frost protection and may be used during heat events to lower temperatures through evaporative cooling. Sprinklers increase moisture in the canopy, however, which increases disease pressure. They are inefficient, since water is lost to evaporation, and expensive to install. Under flood irrigation, the vineyard is flooded with water diverted from a nearby water source. While no longer common, this is still used in Chile and Argentina. Flooding the soil can stymy root growth, but it can also be effective at disrupting populations of phylloxera, and vineyards may be flood irrigated several times per season.

Harvest

Harvest is a busy time in the vineyard. Each pick requires the coordination of labor, equipment, and transportation. These logistics must be responsive, since picks are decided only a few days ahead of time and plans may be impacted by inclement weather and other unforeseen events. Collaboration and flexibility on the part of both vineyard manager and winemaker are necessary to achieve the best expression from the land. 

A number of factors influence a winemaker’s decision of when to harvest, including levels of sugar and acid, tannin texture, and flavor profile, along with practical considerations like winery capacity and weather. From a grower’s perspective, an earlier harvest is often desirable, as this ensures the safety of the fruit—waiting can risk damage from weather or disease. Rain or irrigation can cause fruit to swell and may dilute sugar, acid, and flavor concentration. However, water stress during the ripening period can concentrate the fruit through dehydration. Producers who purchase fruit often pay for grapes by the ton, but since dehydrated fruit weighs less, a grower may prefer to irrigate close to harvest, while a winemaker might prefer extra concentration. This is another reason why acreage contracts are becoming increasingly popular.

Fruit is vulnerable to damage and oxidation from the time it comes off the vine until it is safely in tank. Keeping the fruit safe, intact, and cool is of upmost importance and requires that picks occur quickly and smoothly. In warm regions, fruit may be harvested during the night to keep it cool.

Traditionally, fruit has been harvested by hand. Harvest season is a time of celebration, since it represents the culmination of a year’s work. In Europe, students and townspeople were often enlisted to join in the festivities. Today, cost and labor limitations force growers to consider alternative methods. Mechanical harvesters are improving each year; the technology is promising and may eventually surpass hand-harvesting from a quality perspective. As with mechanical pruning, specific vineyard architecture is required for machine harvesting. In some areas, like New Zealand, it is standard. The distinctive style of New Zealand Sauvignon Blanc has even been attributed to the use of machine harvesting. While there are exceptions, for producers that prioritize quality, hand-harvesting is still the standard.

Once harvest is finished, the vineyard work for the year is nearly done. If there is no rain, the vines may be fertilized or irrigated to help them store sufficient reserves for the following season, and cover crop seeds may be sown. Autumn is also the best time to identify and remove diseased vines, since symptoms are generally most severe at the end of the season.

Pests & Diseases

Pests and diseases threaten vineyard health and longevity as well as the quality and quantity of the current season’s fruit. An essential part of a viticulturist’s job is to diagnosis, treat, and prevent these ills.

Pests

Some vineyard dwellers are helpful, preying on undesirable insects and fungi. Others, however, vector disease or damage the fruit or vine directly, preventing proper growth and development by inhibiting photosynthesis or nutrient uptake. Phylloxera vastatrix, literally “the devastator,” is among the most infamous pests. A destructive yellow louse native to the Americas, it now inhabits most vineyard soils worldwide. It was first observed in Europe in 1863 and spread throughout the Continent, destroying vineyards in its wake. Phylloxera feeds on the vine’s roots, and while this is not fatal in itself, the punctures allow infection by pathogens in the soil. Ultimately, this causes necrosis and prevents healthy uptake of water and nutrients. Phylloxera’s damage is slow and can take years to come to fruition, gradually reducing the vine’s ability to successfully ripen fruit and eventually killing it. While Vitis vinifera is highly susceptible, it was discovered in the 1870s that native American grape species are resistant to phylloxera’s damage. As a result, vinifera was grafted to (mostly) American rootstocks.

The use of rootstock has been an effective remedy overall, but there have been missteps. AXR1, a rootstock used commonly in California during the 1900s, was initially believed to be phylloxera resistant and later proven not to be, resulting in a second round of attack by phylloxera and massive replants. Several rootstocks still used today may not be as resistant as was once thought. There are still wine regions, however, that are reasonably phylloxera free, including Washington State, parts of Southern Australia, Argentina, and Chile. In Australia, strict quarantine protocols limit phylloxera’s spread. Sandy soils and those that flood regularly (including by flood irrigation) are fairly inhospitable to the aphid.

Nematodes are native to Europe and Asia. Similar to phylloxera, they are parasites that feed on roots, ultimately limiting the capacity of the vine to uptake water and nutrients. Several species of nematodes are found in viticulture. The best known of these is the dagger nematode, Xiphinema index, which vectors fanleaf virus. In soils that are affected, the practice of leaving soils fallow for several years prior to replanting is helpful. Certain cover crops, like mustard, are believed to produce toxins unfavorable to nematodes, discouraging their proliferation. Nematode resistant rootstocks—for example, O39-16—may also be used.

Mites are very common in vineyards as well. Some are damaging, while others are beneficial. They feed on leaves, making small brown galls or causing discoloration and reducing the vine’s photosynthetic capacity. Usually, this isn’t serious, but if mite populations grow out of control, they can delay ripening and may even result in defoliation. While chemical treatments are available, many use cultural and biological controls instead. Mites thrive in dusty conditions, so dust should be kept at a minimum when driving through a vineyard. Predatory mites feed on undesirable mite species and can be released into the vineyard to slow their damage. Several organic and non-organic treatments are available to effectively control mite populations should counts exceed established economic impact levels.

Many other insects call the vineyard home. Mealybugs vector leafroll virus, and glassy-winged sharpshooters vector Pierce’s disease. Other species, like the suzukii fruit fly and the European grapevine moth, damage the fruit and open it up to infection by botrytis and other pathogens.

Insects are differentiated by the type of feeding that they do, and this is key to diagnosing which insect is culpable for damage. Sucking insects include leafhoppers and sharpshooters, while cutworms and beetles are chewing insects. To limit damage, predatory insects, like ladybugs that will prey on immature leafhoppers and aphids, may be released. Host plants may be removed from the area or planted nearby to divert insects out of the vineyard. Mating disruption is a technique in which pheromones are released, making it difficult for insects to find each other and mate successfully. When necessary, pesticides can also limit insect populations.

Birds and mammals are incredibly destructive in vineyards as well. Their feeding reduces yields and injures fruit, which encourages disease, and larger animals may damage vineyard infrastructure. Wild boar are a key concern throughout Italy, France, and Germany. In South Africa, baboons walk down vineyard rows “harvesting” clusters as they pass, and in Australia, kangaroos can eat up to 150 kilograms of fruit in a day. In the United States, bird damage is estimated to cost vineyards $70 million per year in losses. Prevention, through bird netting, air cannons, noise emitters, scarecrows, and fencing, may be used in areas where animals pose a threat. Nearly all vineyards in New Zealand use bird-netting to protect the vines, while some producers in Northern California employ falconers to discourage smaller birds. Bird damage is often most severe in early-ripening vineyards, and some producers interplant small amounts of sacrificial, earlier-ripening varieties, in hopes that the birds will eat them and move on.

Diseases

Fungal Diseases

Powdery & Downy Mildew

Powdery and downy mildew are native to North America. While indigenous American grape species are largely resistant to these fungal diseases, Vitis vinifera is highly susceptible. Dormant mildew spores overwinter in buds and bark, and under favorable conditions, they multiply and cause infection. Both powdery and downy mildew can result in devastating crop losses. 

Powdery mildew (oïdium in French) was first described in 1834 in the United States, and it ravaged Europe 10 years later. It is caused by the fungus Erysiphe necator (also known as Uncinula necator). Under warm, damp conditions, spores are carried by wind and infect green plant tissue. Mildew’s spread is temperature dependent, with the greatest success between 70 and 85 degrees. Powdery mildew is most detrimental from budbreak until veraison, when it can grow on berries. It causes small, web-like, fuzzy patches on leaves and fruit as well as black scarring on canes. 

Growers treat powdery mildew with vineyard sprays of sulfur or systemic fungicides on the canopy, generally at regular intervals throughout the growing season. (Note that the elemental sulfur used as a fungicide in the vineyard is distinct from the sulfur dioxide used in the winery.) Control is especially important at budbreak and bloom, since infections on immature plant tissue can spread quickly. Sulfur is typically applied every 10 to 14 days from budbreak until veraison, systemic fungicides every 21 days, and organic biological fungicides, such as Serenade and Sonata, every 7 days.

Vineyards are sometimes threatened throughout the growing season, or the danger could be more intermittent. A dry, warm climate may require 8 to 10 sprays, while at-risk climates may demand over 12 sprays per year. Some producers are able to spray less through careful vineyard monitoring when conditions are favorable. To reduce applications, some viticulturists in the Napa Valley use indicators such as mathematical models or spore traps, which assess the risk of infection, and treat only when the threat is sufficient. Canopy management choices can also minimize risk. Canopies with good airflow are less mildew prone, and the efficacy of sprays depends on coverage, which is easier to achieve on open canopies.

Some grape varieties, including Cabernet Sauvignon, Carignan, and Chardonnay, are more susceptible than others. Merlot, Pinot Noir, Riesling, and Zinfandel are less severely affected. Mildew-infected berries are generally excluded from production as they contribute unpleasant, moldy, and earthy flavors to wine.

Downy mildew (mildiou in French) is caused by Plasmopara viticola. It is sometimes called Peronospora in Europe (Plasmopara was previously taxonomically classified as Peronospora). It is most successful in warm conditions from 65 to 77 degrees Fahrenheit, but unlike powdery mildew, downy mildew only spreads through water. Regions that receive summertime rain like Northern Europe and the East Coast of the United States are more threatened by downy mildew, while sunny areas including California, Western Australia, and Northern Chile are largely free of it.

Downy mildew attacks green plant tissue, especially young shoots and leaves, and causes oily yellow spots on leaves. Severe infections cripple growing shoots and can lead to defoliation, which will shut down the vine. Berries infected with downy mildew turn green-gray or pink-gray and shrivel. Downy mildew is treated through regular spray applications of Bordeaux blend, a mixture of copper and sulfur that treats both downy and powdery mildew, or systemic fungicides. Sprays are typically applied every two weeks beginning at budbreak, though reapplication is required after rain. Affected fruit is removed through sorting, either on the vine or sorting table.

Bunch Rot

Several microorganisms, including species of fungi and bacteria, cause bunch rot in grapes, which destroys the flavor and integrity of fruit, typically rendering it useless for winemaking. Botrytis cinerea is the most familiar of these. Botrytis is able to penetrate and infect healthy berries. Other bunch rot culprits are opportunists that attack damaged fruit. Sour rot is a form of bunch rot caused by yeast and bacteria that colonizes damaged fruit and produces off-flavors like acetic acid (vinegar).

Botrytis overwinters in canes and clusters and germinates in rainy spring conditions, where 65 to 75 degrees Fahrenheit is ideal for its spread. Bunch rot often begins during flowering. Spores become trapped in flowers and lie dormant until veraison, when sugar begins accumulating in the berries. Rain near harvest and insect, bird, or mechanical damage also welcome botrytis and other infections that feed on the sugar. Infected berries turn brown (white varieties) or reddish (red varieties) and shrivel, sometimes becoming fuzzy and gray. After botrytis has infected berries, other species such as acetobacter can cause sour rot. The best way to avoid botrytis is prevention. Anti-fungal sprays at bloom and prior to bunch closure are particularly important to limit its effects later. Cultural practices that encourage airflow in the canopy, like shoot thinning and leafing, will reduce disease pressure as well. Infected plant material should be removed from the vineyard at the end of the season.

Tight-bunched cultivars are most vulnerable, since spores become trapped within the cluster at bunch closure, and dense, shady, and humid canopies foster disease. Berries have a waxy cuticle that protects them from infection, and many red cultivars produce compounds in their skins that combat botrytis. Chardonnay, Chenin Blanc, Riesling, Sauvignon Blanc, Zinfandel, and Pinot Noir are prone to botrytis, while Cabernet Sauvignon, Merlot, Sémillon, and Muscat are less so. 

Under certain conditions, botrytis infection late in the season can cause a positive result known as noble rot. Sémillon, Sauvignon Blanc, Chenin Blanc, Riesling, and Furmint are all botrytis-prone and used to create some of the world’s most expensive and sought-after sweet wines. Noble rot requires dry conditions so that the fruit remains intact and secondary infection by acetobacter and other pathogens does not occur. 

Trunk Diseases

The trunk diseases are a collection of maladies such as Esca, Botryosphaeria, and Eutypa dieback caused by fungal spores that enter the vine through pruning wounds. Infections in the cordons and trunk decay the plant’s vascular system and prevent the transport of water and nutrients to the vine’s extremities. Brown “cankers” or portions of damaged wood are visible in the permanent wood. Trunk diseases are one of the most serious economic threats to vineyards worldwide and result in premature replanting and vine death. 

Eutypa dieback is caused by Eutypa lata and typically affects only a single spur position before advancing through the rest of the vine. Eutypa causes stunted shoots, shriveled fruit, and small, cup-shaped, chlorotic leaves. Botryosphaeria results in a distinctive pie-shaped wedge inside the permanent wood, and shoots on the vine’s extremities are often undersized. Esca was officially discovered in 1898, but there are ancient references to the disease. It causes black measles to appear on berries and very distinct tiger-striped leaves with scorching along the margins.

The risk of trunk disease is minimized through good pruning practices. Cane-pruning may be preferred over spur-pruning, and antifungal paste may be painted onto wounds to keep spores from entering. Once infection occurs, the portion of cordon with a canker may be removed, and a new shoot retrained in its place, to prevent the infection from spreading further into the vine. 

Black Rot

Black rot is a fungal disease instigated by Guignardia bidwellii that plagues vineyards in humid climates, especially in the Eastern United States and parts of Europe. Spores are released with spring rains and attack young green growth, forming small, reddish-brown circular spots on the leaves and dark lesions on the stems. The best way to avoid black rot is to remove all affected clusters from the vineyard, as the spores will otherwise overwinter in the plants. Copper-based fungicides are also effective.

Bacterial Diseases

Pierce’s disease, often called PD, is caused by the bacteria Xylella fastidiosa, which infects the xylem of vines, preventing the transport of water. Pierce’s disease is vectored by sap-feeding insects like sharpshooters and spittlebugs. It is increasingly common in California but rarely observed in Europe or climates with sufficiently cold winters. Delayed budbreak, stunted growth, and fruit dehydration are common symptoms, and they are further exacerbated by drought. Pierce’s disease is identified by uneven shoot lignification, and “matchsticks,” which are petioles that are left on shoots after leaves defoliate. Infected vines will typically die within two to five years, but cold winter conditions seem to extend the life of some vines. 

There is no treatment for Pierce’s disease, and infected vines should be removed to reduce spread. The insects that vector PD live in riparian areas, so nearby vineyards are generally at greatest risk. Building a barricade of plants, such as PD-resistant vines, has been suggested as an effective means of control.

“Grapevine yellows” describes several phytoplasmic diseases, including Flavescence dorée, that are primarily found in Southern European wine regions. Phytoplasms are a specialized type of bacteria that infect plants’ phloem. Delayed, abnormal shoot growth, discolored leaves that curl downward, and berry dehydration are symptoms. Because the shoots do not lignify, infected vines are easily identified by their green shoots in the fall. Leafhoppers are a primary vector of grapevine yellows, so control of these insects is key to slowing the spread, as is removal of any diseased vines.

Crown gall, caused by the bacteria Allorhizobium vitis (previously known as Agrobacterium vitis), is the most common disease of nurseries worldwide. It infects vine tissue during grafting, and later, galls form at the graft union and girdle the vine.

Bacterial blight, caused by Xanthomonas ampelina, kills young shoots. It is spread by rain and on pruning tools, and it can be controlled by copper sprays such as the Bordeaux mixture. Blight is found in South Africa, Southern Europe, Argentina, and Australia.

Viral Diseases 

Grapevine leafroll virus causes significant reduction in yields and slows fruit maturation. On red varieties, leaf margins turn red while veins remain green, and the leaves of white varieties turn yellow. In both cases, the leaves fold downward. Mealybugs are the primary vector of leafroll and are transported throughout regions by birds, wind, and on equipment and workers’ clothes. Leafroll is treated by removing infected vines and through suppression of the mealybug population. One popular treatment is sexual confusion, where tags with mealybug pheromones are placed throughout the vineyard to disrupt mating. In warm regions, where fruit ripens quickly, some winemakers may view leafroll as beneficial, but there are more effective methods to delay maturity.

Grapevine fanleaf virus reduces yields and fruit quality and shortens the lifespan of a vineyard. Infected vines often exhibit abnormal asymmetric leaves, a yellow mosaic pattern in the leaf margin, and yellow bands along the veins. Millerandage is a symptom. Fanleaf is typically introduced to a vineyard through infected planting stock, and afterward, it is vectored by the nematode Xiphinema index. Once fanleaf has been introduced, it is difficult to remove from a vineyard, particularly as nematodes are able to transmit the virus even after the vineyard has been fallow for years. Nematode resistant rootstock, such as O39-16, may be used during replanting. 

Red blotch disease is attributed to a virus discovered in California in 2011. It lowers wine quality by delaying and even preventing ripening. Infected leaves from red cultivars exhibit a distinctive red mosaic appearance, with red veins, that is sometimes mistaken for leafroll virus.

Best Practices 

The spread of pests and disease can be limited by following a set of best practices. Care should be taken to avoid carrying soil or insects on equipment, shoes, clothing, and shears from vineyard to vineyard, especially if a diseased vineyard has been identified. Pruning shears and other equipment must be cleaned prior to use. Dead plant material, especially from infected vines, should be removed during winter pruning to prevent pathogens from overwintering there. In some cases, the removal of diseased vines will prevent neighboring vines from being infected. During vineyard establishment, only vines that have been tested and certified to be free of virus should be used, and a thorough inspection can minimize the risk of introducing infected planting material. This is also why growers are encouraged to import new plant material through nurseries equipped to do so safely, rather than bringing in so-called suitcase clones themselves.

Farming Philosophies

After the end of World War II, many chemical resources that had gone toward the production of explosives became destined for a new fate: commercial NPK-based fertilizers. This heralded a cultural shift in agriculture and the proliferation of the “better living through chemistry” mentality. By the time the 1970s came around, a lot of farmland had been overworked and overfed. Organic farming and its successors are seen as a backlash to these newer ways of farming, today known as conventional agriculture.

Wine grapes are often farmed with quality in mind. While sustainable farming has not been shown to make better wines, the belief that this is probably the case leads to alternative practices. Indeed, many of the most esteemed wine estates throughout the world employ some form of non-conventional farming. As consumer demand for healthier and more environmentally friendly products increases, producers continue adopting more sustainable practices. 

Organic Farming

Organic farming, popularized in the 1970s as the antidote to industrial agriculture, avoids the use of synthetic chemicals that are commonly used in farming. These include conventional fertilizers, herbicides, pesticides, and systemic fungicides. (Organic farming also prohibits the use of genetically modified organisms, or GMOs, but since these are not accepted in the wine industry, this is not a point of distinction in viticulture.) The transition from conventional to certified organic agriculture takes at least three years and requires ongoing audits. A number of organizations worldwide grant organic certification, including the United States Department of Agriculture (USDA), Bioagricert, Agriculture Biologique, and Australian Certified Organic. 

Varied practices fall under the umbrella of organic farming. On one end of the spectrum, organic agriculture resembles conventional agriculture but with organic products replacing synthetic chemical inputs. Other growers go “beyond organic” and seek to minimize inputs, improve the soil, encourage biodiversity, and even look after the spiritual health of the vineyard. This range of beliefs and emphases has led to further delineation of various farming schools of thought.

Many of these philosophies share a common set of values:

• Intolerance of chemically synthesized fertilizers, herbicides,
  fungicides, and insecticides.
• Preference for complex forms of fertilizer like compost, fish emulsion, and
  cover crops, rather than mineral-based fertilizers.
• Vineyard-floor practices that build soil organic matter, preserve
  soil structure, and increase fertility.
• Encouragement of biodiversity, both in the soil and on the farm.
• Holistic, systems-based thinking and decision-making for long-term results. 

Biodynamic Farming

Biodynamic farming shares many of the principles of organic farming but includes extra inputs. It was originally proposed by Austrian Rudolph Steiner, a controversial figure in his time, in a series of lectures given in 1924. While sometimes described as a more premium form of organic farming, the key distinction between organic and biodynamic farming is the annual application of nine biodynamic preparations, applied to the vineyard in homeopathic quantities. Biodynamic farming is also unique for its spiritual nature. Practitioners may elect to farm by the moon calendar, which has been used traditionally in farming and is still mentioned in the venerable Farmer’s Almanac, or the biodynamic calendar, a sort of astrology for plants developed by Maria Thun beginning in 1962. Demeter is the primary biodynamic certification granted throughout the world, and Biodyvin and respekt-BIODYN are smaller regional organizations. 

For decades, non-conventional farmers had the option to self-identify as organic or biodynamic. But while many farmers wish to go beyond the basic requirements of organic agriculture, the emphasis of biodynamics on the nine preps and its adherence to the cosmos are not priorities for some seeking a more environmentally friendly approach.

Regenerative Agriculture

Regenerative farming is viewed by some as the next frontier of organic farming. Whereas organic farming takes a stance of “do no harm,” regenerative farming seeks to go further, actively improving the land through soil building, nurturing microbial ecosystems, and advancing the health of the vineyard. Its ultimate goal is to reduce climate change through carbon sequestration, or removing carbon dioxide from the atmosphere. Regenerative agriculture is heavily influenced by teachings from the Rodale Institute and the Weston A. Price Foundation, and while there is currently no certification, some programs are being developed. Mimi Casteel of Hope Well Vineyard in the Willamette Valley is one of the leading voices for regenerative agriculture within the wine community.

The focus of regenerative agriculture is, fundamentally, on management of the vineyard floor. Building organic matter in the soil, preserving soil structure by no-till practices, and the use of cover crops encourage soil health and prevent erosion. Regenerative farming is sometimes mistakenly described as “do-nothing farming.” At its best, regenerative farming is very active and requires careful observation and decision-making. 

Sustainable Farming 

Sustainable farming, called lutte raisonée in France, has been used as a catchall to describe a range of growing practices. On the one hand, it could be thought of as a more pragmatic alternative to organic farming, since producers are free to intervene when necessary. Yet sustainable farming also encompasses a wider range of values than organic farming, including the responsible use of resources like water, power, and fuel. While sustainable farming is generally unregulated, several regional certifications have been created to offer better definition of the concept. These programs look at vineyard inputs and practices as well as use of resources (such as water and electricity), business sustainability, and even labor practices. Many of them encourage continual, gradual improvement, such as doing fewer sprays in a year, eliminating the use of herbicides, or reducing water use. Examples include Sonoma County Sustainable, Napa Green, Lodi Rules, SIP Certified, and LIVE. The Porto Protocol, formed in 2019, is a global initiative that encourages growers to adopt practices that combat climate change. 

Integrated Pest Management 

Integrated Pest Management (IPM) is essentially a systems-based approach to treating vineyard pests and diseases. Rather than treating a symptom, IPM encourages producers to identify and treat root causes or adjust the environment to make conditions less favorable for pests and disease—requiring an understanding of their lifecycles. IPM emphasizes the use of biological and cultural controls over chemical controls such as insecticides and fungicides. It treats maladies by exploiting predator-prey and host relationships, habitat manipulation, physical barriers, and biological interventions like mating confusion. 

Other Considerations

There are a number of reasons that a producer may generally adhere to particular farming practices but not choose to seek certification, even if it might offer a point of distinction. Certifications are expensive, labor and paperwork intensive, and disproportionately costly to small operations. Some prefer to instead spend that time improving their farming practices. For producers that do not intend to use certification for marketing purposes, the effort and cost might not make sense. Others prefer the flexibility to use treatments in case of an emergency.

While many have moved in the direction of more sustainable practices, there are practical limitations to farming non-conventionally. Most vineyards are businesses and must be economically viable. Non-conventional agriculture can be more costly; at a minimum, it requires more vineyard oversite than conventional practices. In challenging climates, chemical-based disease control can be more effective than its organic counterparts, which might result in yield and quality losses. 

With any vineyard philosophy, there are trade-offs, and dogmatism can ultimately do more harm than good. For example, organic sprays often must be applied more frequently than conventional ones, which requires tractors to pass at least twice as often, increasing compaction and burning more fuel.

The Future of Farming

Vineyard Labor 

In many regions, agricultural work is done by a migrant labor force that travels to the region only during the growing season. This is driven by economic disparities that make it more profitable for these workers to pursue employment far from home. But political constraints, housing shortages, better economic opportunities at home, and the strain this schedule places on family life are rapidly disincentivizing migrant labor. Many agricultural communities rely on what is ultimately an unsustainable model, and labor shortages pose a real threat. 

A reduction in the workforce increases labor costs, ultimately impacting bottle price. On the top end, this may be surmountable; however, for some producers, hand-labor is rapidly becoming cost-prohibitive. In some regions, labor is not available at any price. As a response, many producers are forced to consider increased mechanization in the vineyard.

Vineyard Mechanization

As more traditional farming practices grow in popularity, an equal and seemingly opposite trend is the rise of mechanization and technology in the vineyard. Certain tasks are widely mechanized, including ploughing, mowing, hedging, and spraying. Others, like leafing and suckering, are reasonably easy to mechanize, while some operations, such as pruning, are more difficult to mechanize without a loss in quality.

Mechanization is more responsive, faster, and cheaper than doing the work by hand, which may allow better timing with grapevine phenology. It requires significantly less labor, and technology is improving each year, sometimes resulting in better wine quality than hand labor. However, currently, mechanization is not as precise as hand work for many tasks and can damage the fruit or vine. It requires specific vineyard architecture, and many established vineyards would need to be retrofitted in order to use it. Mechanization also changes the culture of grapegrowing, eliminating the human element and traditional ways of working.

While the wine industry has been much slower to adopt mechanization than other forms of farming, it is widely acknowledged that in the future, many tasks currently done by hand will likely be done by machine.

Precision Viticulture

Increased mechanization has also paved the way for an emerging field known as precision viticulture, which uses extensive data collection and artificial intelligence (AI) to improve quality and efficiency. A number of interesting vineyard monitoring tools are being developed. Tractors and drones equipped with cameras are used to create vineyard maps with data collected on a vine-by-vine basis. Mapped data might include areas of water and nutrient stress, color accumulation, the degree of fruit ripening, yield estimates, and diseased vines. 

Precision viticulture seeks to minimize overtreatment and can be used to support sustainability through resource conservation. For example, variable irrigation schemes irrigate or fertigate vines based on their specific needs, saving huge amounts of water. Additionally, equipment is being designed to reduce the amount of product needed. While the technology has not yet been perfected, electrostatic fungicide sprayers release a fine mist of particles that are attracted electrostatically to the vine, providing better coverage with less volume.

The mechanical pruners of the future will likely be programmed with artificial intelligence and “taught” to prune vines as a human would. AI could be used to train machines to do a number of farming tasks, likely at a fraction of the cost and time they take today. It is possible to imagine each individual vine being farmed to a particular specification to optimize quality and yields.

Precision viticulture allows for the acquisition of data for better decision-making, cost reduction, and conservation of resources like water and labor. Overall, it presents many potential benefits, especially for the value segment of the market, but many producers are wary of this vision of the future. The quest for optimization requires a target and is often met with standardization; whenever many producers emulate a specific wine style, it is at the detriment of diversity. The challenge of precision viticulture will be the emphasis, and not erasure, of terroir.

Looking Ahead

Viticulture is an ever-changing science. As more is learned about biological systems and plant function, and as climate and palates evolve, viticulturists must continue to adapt and rethink beliefs that have driven decision-making for years. What is fixed, however, is the interdependence of the vineyard system, which combines human inputs, the environment, and the vine’s natural inclinations, as dictated by genetics. The viticulturist spends all season tending grapes with the goal of delivering healthy, ripe fruit and adequate yields at harvest; from here, the process is in the hands of the winemaker.

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Compiled by Jennifer Angelosante (September 2020)

Edited by Stacy Ladenburger