October 19, 2011

Green Cropping

    Removal of unripe grape clusters from vines to encourage better development of the remaining clusters. Some of the best growers remove up to half the crop.

An important determinant of wine quality is vineyard yield: the total amount of grapes or juice produced by the vines. Yield is normally measured in tons per acre or hectolitres per hectare. Let’s stick with tons/acre for now.

A grapevine can deliver only so much nutrients through its trunk and branches (canes). This nutrient mix is then distributed to all the grapes in all the clusters of the vine. Each  cluster will be treated equally and receive a portion of the nutrients. And the more clusters and grapes there are, the less there is to go around. We can improve this distribution by cutting down on the number of clusters, giving the remaining grape more of the available nourishment.

The optimal yield for a vineyard depends on the type of grape and the eventual wine quality. Factory wines or jug wines may come from vineyards that produce 10 tons/acre and even more. But with a quality wine, we want to cut down the yield, and the simplest way to do that is to remove grapes. This is done about the time the grapes begin to change colour and texture, from rock hard green marbles to something more resembling a grape.

Ask a vineyard manager or winemaker about yield and they’ll often proudly state a low yield figure such as 2 ½ tons/acre and even less  – again, depending on the  type of grape. It’s not uncommon for highly desirable wines to come from vineyards that were green-cropped down to 1 ½ or even 1 ton/acre.