Vineyard Factors Influencing Rootstock Selection

There are several factors that influence rootstock selection in the vineyard. A rootstock is the lower part of a grapevine and its rooting system, onto which a scion, or fruit-bearing cutting, is grafted to form a new plant with the desired qualities of both parts. In most cases, the rootstock is from an American grapevine species, or crossing or hybrid thereof, whereas the scion is from Vitis vinifera descent. Before planting, it is important to understand the soil composition and other factors that may influence how the grapevine will behave once planted. Rootstocks are selected for a number of reasons, including their resistance to pests such as phylloxera and nematodes; their tolerance to lime, soil salinity, drought, wet conditions, and cool temperatures; their ability to root; their compatibility with the scion; and commercial availability.

Resistance to phylloxera is a significant factor influencing the choice of rootstocks. Phylloxera is an aphid indigenous to the eastern United States that spread throughout most of the world’s wine regions in the late 1800s, destroying most grapevines of the Vitis vinifera species. It was the original reason that grafting was first used in viticulture, and due to its ubiquity today, it should remain a primary consideration when selecting a rootstock. The pest can be found above and below ground, but it is the phylloxera found below that causes the most damage to grapevines. When feeding on roots, these pests disrupt the translocation of water and other nutrients in the vine and create entry points for fungi and bacteria, which enter the plant and eventually kill it.

There are certain wine regions, including Chile and South Australia, where phylloxera has not yet traveled, and there are soil types, like those high in sand found in Mendoza, Argentina, and Washington’s Columbia Valley, that are inhospitable to phylloxera. However, outside