Growing Grapes in Your Backyard
leaves of SO4 rootstock
Wine grape scion varieties are nearly all of Vitis vinifera parentage. This species is prone to attack by two root pests, grape phylloxera and parasitic nematodes. Vitis vinifera vines can be protected from these pests by grafting them to rootstock varieties derived from other vine species and resistant hybrids. Many of the rootstocks used for this purpose are adapted to particular soil types, chemistry and fertility. They may also be used to overcome vineyard problems such as drought, excess water, and salinity.
Own-rooted vines (rooted cuttings) are typically sold in retail nurseries and work fine in most home gardens. However, rootstocks are appropriate in areas where grapes cannot be grown on their own roots because of nematode and grape phylloxera infestation, or in old vineyard areas that are being replanted. Several rootstocks are nematode-resistant and possess moderate phylloxera resistance. The varieties used most frequently as rootstocks are Freedom and Harmony. In coastal areas one of the following phylloxera-resistant rootstocks should be used: SO4, 5BB, 110R, 99R, or St. George.
Rootstocks - UC Integrated Viticulture Online