Why Almost Every Wine Grape Grows on American Roots

Roughly four out of five wine grapes you have ever tasted grew on roots belonging to a different species — an American vine, joined to a European one just above the soil.

Grapevines are grafted because of an insect. When phylloxera devastated Europe’s vineyards in the late 19th century, growers discovered that American vines survived what killed their own, and the industry was rebuilt on a compromise: European fruit above ground, American roots below. That emergency fix became permanent — and then became a tool. Here is how grafting works, and why growers now choose rootstock as carefully as they choose the grape.

The two halves of a grafted vine

A grafted vine is two plants fused into one. The scion — the upper part, bearing the buds, shoots, leaves and fruit — is Vitis vinifera, the European wine grape: Chardonnay, Cabernet Sauvignon, Pinot Noir. Everything you taste comes from the scion.¹

The rootstock is a different, usually American, Vitis species or hybrid. It never produces the wine grapes; it produces the root system. The join between them is the graft union, the visible knuckle just above soil level — and it must stay clear of the soil, or the scion roots itself and loses the protection. Roughly 80% of the world’s vinifera grows this way.¹²

Why it works against phylloxera

Phylloxera attacks roots. American Vitis species evolved alongside the insect and defend themselves — sealing feeding wounds with callus tissue so the vine is not girdled and the secondary rot that finishes off a European vine never takes hold. Vitis vinifera, which never encountered the insect, has no such defence.²³

Grafting exploits that split precisely. Put the vulnerable part where the insect cannot reach it — above ground — and put a resistant root system where the insect lives. The vine is still attacked; it simply survives. This is why phylloxera was never eradicated and does not need to be: the defence is built into the plant. Resistant rootstock and naturally sandy soil are the only completely effective protections — no pesticide eradicates it.³

Where rootstocks come from

Most commercial rootstocks descend from three American species, each contributing a different strength:⁴⁵

• V. riparia — the riverbank grape. Devigorating, hastens ripening, dislikes drought.
• V. rupestris — the sand grape. Vigorous, deep-rooting.
• V. berlandieri — tolerant of drought and, crucially, of the chalky limestone soils that defeated the earliest American imports.

That last point mattered enormously. The first American vines brought over failed in France’s limestone soils, turning yellow with chlorosis — one of the strongest arguments used against grafting during the crisis. Breeding berlandieri into the mix solved it, which is why so many modern rootstocks are crosses rather than pure species — there are no pure berlandieri rootstocks, because it roots poorly from cuttings.⁴⁵

The workhorses

From emergency fix to precision tool

Growers quickly realised the rootstock does far more than survive phylloxera. It regulates vigour — field comparisons put the most devigorating stocks at roughly 60–70% of the most vigour-inducing ones, close to a two-fold spread in vine size — and with it canopy size, yield and ripening date. It governs drought tolerance through rooting depth, lime tolerance on chalky soils, and nutrient uptake.¹⁶

So rootstock choice is now a site-matching decision made before a vineyard is planted, and one a grower lives with for decades. A vigorous rootstock on fertile soil produces a jungle of leaves and dilute fruit; a devigorating one on poor dry ground can starve. In a warming climate, drought-tolerant rootstocks have become one of viticulture’s most-discussed adaptations.⁶

Does grafting change the taste?

This was the great fear during the reconstitution, and it has never entirely gone away. The honest answer: the rootstock contributes no aroma compounds of its own — the fruit is the scion’s — though it does alter berry mineral content, but it shapes the conditions that produce flavour, through vigour, water uptake and ripening speed. Advocates of ungrafted, own-rooted vines in Chile, Santorini or the Barossa argue the difference is audible in the glass; sceptics note that vine age, site and yield are confounded with root type in almost every comparison. It remains one of wine’s genuinely open questions.²⁶

Read more

• Phylloxera: how one insect nearly ended wine — the crisis that made grafting universal
• All our phylloxera coverage
• Pinot Meunier: Champagne’s third grape
• The history of wine: a complete timeline

References

1. eXtension Grapes, “Factors to Consider when Selecting Grapevine Rootstocks.” ↩
2. Phylloxera — grafting as the only successful control; American Vitis resistance mechanisms (corroborated). ↩
3. Benheim et al., “Grape phylloxera — a review,” Annals of Applied Biology, 2012. ↩
4. WineWiki, “Phylloxera & Rootstock Selection (SO4, 110R, 3309C, 101-14, Riparia Gloire).” ↩
5. Progressive Viticulture, “Selecting a Rootstock for a Wine Grape Vineyard.” ↩
6. Chen et al., “Rootstocks for Grapevines Now and into the Future,” Australian Journal of Grape and Wine Research, 2024. ↩

Want to read more? Try these books

Wine Grapes Robinson, Harding & Vouillamoz

Phylloxera Christy Campbell

The Oxford Companion to Wine Jancis Robinson (ed.)

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