Pruning has two phases: winter vine thinning and summer foliage trimming. With winter pruning, your goals are to eliminate crowding, select growth points for this year's crop and set the stage for next year's crop. Late winter to early spring is the best time for vine pruning -- when the worst winter weather is behind you but before spring blooms appear. At Three Sisters Vineyard, pruning begins in December and wraps up by early March.
"Grapes store energy in their root balls," Paul said. "You don't want to drain off energy too early."
Vines pruned too early are also more susceptible to fungal disease. Fall rains splash fungal spores up from the ground onto the plant, where fresh pruning cuts are susceptible to infection. Summer pruning involves hedge trimming the leaves.
"During the summer growing season, leaves provide shade around the fruit, but within the last month before harvest, you want to remove some foliage," Paul explained. "You also want to keep the vines off the ground."
Most wine grapevines are grafted onto disease-resistant root stock. If vines touch the ground and begin to root, they lose the benefit of the hardier root stock and become vulnerable to disease.
See how much to prune on the next page.