🌿 Canopy (grape)

The canopy of a grapevine is its shoots and leaves above ground. Canopy management changes its density and layout to bring vine growth and fruit into balance.

The leaves make the vine's sugars by photosynthesis. According to the AWRI, each leaf is photosynthetically active for about three months and works at its best about midway through that time. Shading matters for the next year too: heavy shading of developing buds and their leaves lowers bud fruitfulness, and so the number of inflorescences the following season, while buds most exposed to sun have the greatest potential.

Shoot thinning removes selected shoots to reduce shoot density and the number of clusters per vine. Penn State Extension advises doing it after the last expected spring frost, when shoots are about 5 to 6 inches (13 to 15 cm) long and no more than 10 to 12 inches (25 to 30 cm). Its targets per linear foot of canopy are 3 to 5 shoots for Vitis vinifera, 4 to 6 for most hybrids and up to 15 for Concord and other native cultivars.

Fruit-zone leaf removal takes leaves from around the clusters. It exposes them to more sun and warmth, improves airflow so that fruit dries faster after rain or dew, helps fungicide reach the clusters and lowers bunch rot compared with shaded clusters. The recommended window is after fruit set, from the baby berry to the pea-size stage. A fruit zone with zero to two leaf layers generally has less rot and better quality potential than a denser canopy.

Sun-exposed fruit tends to have a higher sugar-to-acid ratio, more norisoprenoids and fewer methoxypyrazines. Results depend on cultivar, vintage and how much fruit is exposed. Completely defoliating the fruit zone in mid to late summer is not advised, because berries that grew in shade can suffer sunscald.