Wine myths
Old vines make better wine
“Old-vine wine is better because the roots go deeper.”
Old vines yield less and more consistently, which helps. The deep-roots explanation is largely unevidenced, "old vine" has no agreed legal definition in most places, and survival bias does much of the work.
The full answer
Vine age has real consequences. Yields fall, and older vines are often reported as more consistent from vintage to vintage, buffering against extremes. Both are plausible contributors to quality.
The deep-roots story is much weaker than its popularity suggests. Root depth is governed principally by soil structure, water table and rootstock; a young vine in deep permeable soil can root further than an old vine sitting on rock.
Survival bias explains a great deal. Vineyards that were unproductive, badly sited or planted to unfashionable varieties were pulled out decades ago. The old vines that remain are disproportionately the ones somebody thought worth keeping.
"Old vine", "vieilles vignes" and "viñas viejas" are not legally defined in most jurisdictions, so the term on a label can mean thirty years or a hundred and twenty, and sometimes means neither.
Genuinely old vineyards are a finite, irreplaceable resource and often make distinctive wine. The point is that the age is one factor among several, and the mechanism usually given for it is not the real one.
A relationship that has been measured across real samples — a correlation between growing-season temperature and harvest sugar, say — without a single demonstrated mechanism covering the whole path from cause to effect.
What would settle it: A larger or better-controlled study finding no association.
Sources
Sources consulted
- UC Davis Department of Viticulture and Enology — University of California, Davis
- Barossa Australia — Barossa Australia
- The Oxford Companion to Wine — Oxford University Press