Rootstock
Viticulture · Intermediate · 3 min read
A rootstock is the root system of a grapevine, onto which a scion (the upper part that produces the wine grapes) is grafted. Almost all wine vines worldwide are grafted onto phylloxera-resistant American rootstocks, the standard response to the 19th-century phylloxera crisis. The choice of rootstock affects the vine's vigour, drought tolerance, soil adaptation and yield, and is one of the most important decisions in establishing a vineyard.
Why rootstocks exist
European Vitis vinifera is highly susceptible to phylloxera, a tiny insect that attacks and kills the roots. American species, evolved alongside the insect, are resistant. The solution, developed in the 1880s, was to graft the desired Vitis vinifera variety onto a resistant American rootstock. The scion produces the wine grapes; the rootstock provides the resistance.
Today, almost every wine vine in the world is grafted. The exceptions are a few phylloxera-free regions, such as parts of Chile, Washington State and South Australia, where own-rooted vines are still planted. The UK, despite its cool climate, is not considered phylloxera-free, and all commercial UK plantings are grafted.
Common rootstocks in the UK
The most common rootstocks in UK vineyards are 3309C, 101-14, 5C, SO4 and Riparia Gloire. Each has a different profile. 3309C is a vigorous, deep-rooting rootstock suited to deep, well-drained soils. 101-14 is lower vigour, suited to shallow or drought-prone soils. 5C is a versatile middle-of-the-road choice. SO4 is vigorous and tolerant of chalky, alkaline soils. Riparia Gloire is low vigour and suited to deep, fertile soils.
For chalky sites, which dominate the South East, 41B and Fercal are popular because of their tolerance of high pH and active lime. For sandy East Anglian sites, 101-14 and Riparia Gloire are common. The choice is made at planting and stays with the vineyard for the life of the vines.
How rootstocks shape the wine
The rootstock does not directly affect the wine's flavour, but it shapes the vine's behaviour in ways that do. A vigorous rootstock on a fertile site can produce too much leaf growth, leading to a shaded canopy and under-ripe fruit. A low-vigour rootstock on a poor site can produce a stressed vine with concentrated but tiny fruit. The match between rootstock and site is critical.
In the UK, the typical approach is to plant on a moderately vigorous rootstock such as 3309C or 5C, then manage vigour through cover cropping, irrigation and pruning. A few of the more experienced growers are now experimenting with matched pairs, planting different scion/rootstock combinations in different blocks to see what works best on their specific site.
Sourcing grafted vines in the UK
UK growers source grafted vines from a small number of specialist nurseries, mostly in France, Germany, Italy and the Netherlands. The order is usually placed 12 to 18 months before planting, and the vines are delivered as dormant, bare-rooted plants in the spring. The cost is around 3 to 5 pounds per vine, depending on variety, clone and rootstock.
Some UK nurseries, particularly in the South East, are now starting to graft vines domestically, which gives growers more control over the supply chain. The trend is towards more local production, partly for biosecurity reasons and partly to support the UK wine industry's infrastructure.