Thank you Dustin Chabert and Darla Hoffmann for your input last week on Co-fermentation, take a look if you missed it!
This week: Slopes
How does the angle and exposure of a slope (or lack thereof) influence a vineyard’s growth cycle and fruit quality? Use specific vineyard examples from the winegrowing world to illustrate this impact.
The geographical location of a vineyard is key on which slopes to plant grapes, at what elevation, and at which direction they should face. In the Northern Hempishere south and west facing vineyards are much warmer, where in the Southern hempishere it is the opposite. However, in the Northern Hempishere East facing vineyards receive the first of the morning sun warming soils fast when needed most. Northern slopes should be avoided in cool climates where summers are cool in the Northern Hempisphere. For example, Eastern Washington and Germany are at higher northern latitudes therefore thrive in South and Southwest facing vineyards to maximize sun exposure. Many will use windmachines for frost control. The Mosel has some of the most dramatic South facing slopes with slate soils that absorb the heat. Very careful hand harvesting is usually necessary the more dramatic the slope as machines are not as accessible; there is also the risk of soil erosion and faster rain runoff. Gentle slopes will allow cold air to drain reducing frost injuries and cold winter temperatures. A deeper layer of soil accumulation is more prevalent on gentle slopes and rain tends to stay in the soils longer. Weeds and other crops should be managed as to not act as a barrier to the cold air and suck up water necessary for grape growing. Another example are the vineyards on Mount Veeder in Napa. These vineyards produce grapes with higher tannins and acid than those of the valley floors due to sun exposure, cooler temperatures and diurnal swings. The tannic structure will give the wines more ageability where the valley floor will produce wines with lush ripe, drink now fruit. Buds open later in cooler high elevations and ripening comes later due to being above the fog. Fog can be great for Valley floor vineyards where heat is intense. The Valle de Uco southwest of Mendoza's Eastern slopes of the Andes in the Southern Hempisphere are hot and dry and just about pest free. Water originates from snow melt here, and there can be drastic day to night temperatures. All in all the steepness of the slope, effect of rainfall and sunlight as well as the history of the site including weeds, other agriculture and pest diseases are all of great influence to a vineyard's growth cycle and fruit quality.
I'd add that specific slopes grape varieties like different slopes. Cabernet Sauvignon tends to like soft shoulders of hills, whereas varieties like Reisling can thrive on almost vertical slopes.
It's important to note that a perfect aspect isn't always perfect for every vine. Especially in hot northerly new world areas where sunshine is abundant, some Vines are planted with more north facing aspects to keep them cooler (especially white grapes).
Take into account slope and aspect when planting a vineyard; a variety on a sunny site/warm climate may need to be planted east/west to allow the canopy to shade the grapes, or vineyards in cooler climates may be oriented north/south to maximize exposure as the sun traverses the sky. The sun in the morning is more gentle than afternoon sun and this can also dictate which varieties are planted on eastern vs western slopes. Lastly, prevailing winds may guide vineyard orientation: do you need the vines to run perpendicular to the wine to block it, or parallel to it and direct it through the vineyard (like in cooler, damper regions) to help mitigate mold and fungal pressures? A simple break in a vine row, like a tractor path, may funnel air through the vineyard to ward off issues.