Research is strengthening the long-held belief that old vines produce wines with greater concentration, complexity, and a clearer sense of place. Yet why vine age and deep roots might enhance terroir expression remains an open question.
In November 2025, the Garnachas Históricas project, working with the universities of Navarre and Zaragoza, presented a study of Grenache musts from young and very old vines in Spain’s Campo de Borja. Musts from older vines contained a wider range of aromatic compounds, often at higher concentrations. Their aromas also varied more markedly from one subregion to another, while those from young vines were more alike.
The benefits of old vines are familiar to wine professionals. Older vines tend to yield less fruit and smaller clusters, which can concentrate flavors. Some growers have even grafted new varieties onto established old vines, preserving their mature root systems. At Austria’s Domäne Wachau, for instance, plantings were redirected toward Grüner Veltliner and Riesling between 2005 and 2010 largely by grafting over existing vines. Klaus Peter Keller has also grafted Pinot Noir selections onto old Silvaner vines in the Morstein vineyard, avoiding the long wait for roots to penetrate its resistant limestone.
Root depth is often credited with helping older vines express terroir. The Deep Roots Coalition, a group of California and Oregon growers that advocates dry farming, links its approach to the idea that wine should reflect the place where it is grown. But the mechanism behind any connection between deep roots and terroir remains unclear.
What are deep roots seeking?
Many explanations of how roots affect wine flavor conflict with prevailing views in plant physiology, soil science, and geology. Professor Alex Maltman, whose work appears in the Guild of Sommeliers’ syllabus and The Oxford Companion to Wine, argues that vines obtain humus-based nutrients from the upper soil and other nutrients from relatively shallow layers. Deeper roots, he says, primarily seek water. He also rejects the idea that complex geology necessarily produces complex wine flavors.
Vineyard consultant Pedro Parra takes a different approach. Known as “Doctor Terroir,” he begins his work by excavating pits roughly 6–10 feet (2–3 metres) deep to examine a vineyard’s geology. He believes a site’s potential is realized through root penetration.
Parra was drawn to Hamel Family Wines in California’s Mayacamas Mountains because fractured basalt allows roots to penetrate the rock. He argued that achieving this required ending the drip irrigation common in many premium California vineyards. Consultant Steve Matthiasson, who advises Hamel, is known for using carefully controlled irrigation to gradually wean vines from it and encourage deeper rooting.
Parra compares young vines to young people accustomed to fast food: they need time to mature. Given favorable conditions and no constant irrigation, he believes their roots can eventually reach deeper, more rewarding layers.
Hamel owner John Hamel broadly agrees with Maltman, but allows that moisture and oxygen in rock fissures could weather the stone into finer particles and permit some nutrient uptake. He also says deep-rooted vines seem to produce wines with a more resonant mineral character, greater energy, and a longer finish. He cannot explain the connection, but says he has observed it.
A similar belief has been expressed at Château Canon in St-Émilion. Former proprietor Eric Fournier maintained that vines could express the essence of the estate only after their roots reached the limestone. Older vines, he observed, were the first to show the floral perfume and mineral nuances associated with the wine. The estate describes its porous limestone as absorbing rainwater, with clay-filled cracks retaining moisture—but that account does not explain the perceived change in the wine.
Parra has also encountered limestone with a different effect. At Château Lafite, he attributed certain flavors that concerned the vineyard manager to a local seam of chalk beneath otherwise deep sand and gravel soils. In his view, chalk affects Cabernet Sauvignon at Lafite negatively, while limestone benefits Merlot at Canon.
The remaining puzzle
Parra believes geology’s clearest influence may be felt in a wine’s texture and mouthfeel rather than in aroma or flavor alone. Yet the Campo de Borja study found clear aromatic differences linked to terroir. At Hamel, the basalt influence is often described as “ferrous”—a sensation somewhere between flavor and texture.
Any explanation of how root depth relates to wine character must fit into a broader account of how geology affects flavor. That account remains incomplete, and terroir as a whole has received limited scientific study.
Meanwhile, some growers and writers continue to say that “minerals” pass from soil into grapes, a claim that is biologically untenable and often unclear in meaning. Skeptics such as Maltman, meanwhile, reject geological influence on flavor altogether, despite the impressions reported by tasters.
Parra argues that viticulture research can overlook terroir because scientists focus on what can be measured. But the Grenache study shows how careful analysis can bring researchers closer to understanding the relationship between vines and flavor. Further work may eventually clarify what deep roots contribute to the taste of wine.