Flowering and fruit set

Flowering is the single most weather-sensitive event in the vine’s year for crop size. Nothing later can recover a poor set.

It is also the point at which a vintage’s reputation is often effectively decided, months before anyone tastes anything.

Vitis vinifera flowers are hermaphrodite and largely self-pollinating, a consequence of domestication — wild vines have separate male and female plants, which is why reliable fruiting had to be selected for.

Flowering requires warmth. Cold, rain and wind interfere with pollination and with the vine’s ability to support the developing berries.

*Coulure* is the failure of fertilised flowers to develop, so they drop. It is associated with cold, wet weather at flowering and also with excessive vine vigour, where shoot growth competes with the flowers for carbohydrate.

*Millerandage*, sometimes called hen-and-chicken, is uneven fruit set producing bunches with a mix of normal and tiny seedless berries. The small berries ripen differently, and some producers regard the resulting concentration as an advantage.

Susceptibility varies by variety. Grenache, Merlot and Malbec are commonly cited as prone to coulure; Chardonnay and Gewürztraminer to millerandage.

Poor set can be a quality benefit as well as a yield cost: a smaller, looser crop of well-exposed bunches can ripen better and resist rot more effectively.