Key Considerations When Choosing Grapevine Rootstocks
Rootstocks are employed in vineyards primarily to address: Pest resistance, Environmental (abiotic) challenges, Propagation compatibility, Scion vigor and growth management. Rootstocks are typically only used when site conditions demand it. Ungrafted vines are generally more cost-effective and easier to manage, so they are preferred unless a specific need arises.
Identifying the pests present on a site is the first step in rootstock selection. This is particularly important on previously planted vineyard land, where pest pressure tends to be higher. In nearly all U.S. wine regions, European grape varieties (Vitis vinifera) must be grafted onto resistant rootstocks due to the widespread presence of phylloxera (Daktulospaira vitifolia), a destructive root louse. Some American hybrids and French-American varieties offer enough natural resistance to grow without grafting. Local extension services often provide recommendations indicating whether grafting is necessary for particular varieties.
Nematodes—microscopic soil-borne worms—are another significant pest. However, there is no universal nematode resistance. Rootstock resistance is specific to particular nematode species, so soil testing by a professional lab specializing in vineyard nematodes is essential. Proper sampling technique and timing are key to an accurate risk assessment.
Each vineyard site presents a unique mix of physical, chemical, and climatic conditions. Rootstocks vary widely in their tolerance of factors such as: Waterlogging (poor drainage), drought, salinity, soil pH (acidity or alkalinity) and nutrient deficiencies
Before planting, growers should take corrective steps where possible, such as installing drainage or irrigation systems, or applying soil amendments like lime. Although data on rootstock tolerance to abiotic stressors is often incomplete—and sometimes based on anecdotal observations rather than scientific studies—it's wise to consult multiple sources, especially local university Extension experts, when making a decision.
Rootstocks also differ in how easily they can be propagated. Some varieties, such as O39-16 and 420A, are known to be difficult to graft and may result in higher nursery costs. In these cases, the availability and quality of planting material can be affected. However, a rootstock that is hard to propagate by one method may perform well with another. For instance, while 420A is challenging to bench graft, it can be effectively propagated by field budding.
Rootstocks significantly influence the vigor of the scion (the fruit-bearing portion of the vine). Even under optimal conditions, scion growth can vary dramatically—sometimes two to three times—depending on the rootstock used. Rootstock selection can help balance vine growth, especially when matched against the vigor of both the site and the scion. For vigorous sites and scions, using a low-vigor rootstock helps moderate growth. Conversely, in low-vigor conditions, a more vigorous rootstock can compensate and support healthy development. Since most vineyard situations fall somewhere between these extremes, choosing the right rootstock often involves a careful balancing act. In replanting scenarios, the performance of previous vines can offer valuable insights for rootstock selection.
If pest pressure dictates the use of a high-vigor rootstock in a site that would otherwise benefit from moderate growth, growers may need to adjust their trellising system or use cover crops to limit vine vigor by increasing competition for resources. Selecting the appropriate grapevine rootstock is a critical decision that can significantly impact vineyard productivity and longevity. Because no single rootstock is ideal for all situations, growers are encouraged to gather detailed site information and seek guidance from reputable sources—especially local Extension specialists—before making a final choice.
