How to Thin Grapes
Grape thinning is only one of the important tasks to do for a good fruit crop. The grapevine should be pruned in late fall or very early spring depending upon your zone. The plant also needs to be fertilized before flowers arrive to encourage a larger fruiting. Thinning helps keep fruit from rubbing and gives it room to develop and ripen properly. Good thinning practices also create tight clusters of grapes which travel and keep better than loose, thin clusters. Grapes typically set more clusters than they will have the energy to develop. Removing some of these groups of fruit will allow the vine to concentrate on maturing viable clusters and individual fruit. It also allows light and air into the plant, which enhances overall health. Grape cluster thinning is not difficult. It simply means removing any clusters that are small, misshapen, or even overly large. Thinning grape clusters is done immediately after the flowers have dropped and berries are set.
Berry Thinning of Grapes
Berry thinning removes half of the cluster to allow the remainder enough space to develop larger. Berry thinning is done shortly after cluster thinning and should leave four to five stems on the lower part of the cluster’s stem. When the berries are as large as BB’s, they need to be hand thinned. This is done commercially by professionals who know the optimum size the fruit should become. They remove any berries that are lagging behind in development and will overcrowd the largest, juiciest fruits. Berry thinning is most important in commercial crops where the clusters need to set thickly in order to travel and store best.
