Many grape varieties, especially spur-pruned varieties, require shoot and berry thinning.
When shoots reach 6 to 12 inches, thin them out so
that there are only two shoots to each spur or to each
bud position on the cordon.
The berry clusters also often need to be thinned to allow fewer but larger berries to form. Just
after bloom and berry set, remove the lower third of the clusters or cut alternate side branches
of the cluster.
Six-inch shoot growth stage
Thin after bloom and berry set