You should prune grapevines (Vitis spp.) when they are dormant, from the time they drop their leaves in fall until their buds open in spring. Grapes generally grow in U.S. Department of Agriculture plant hardiness zones 3 and above, depending on the species. If you prune your vines properly, you should have no reason to prune shoots during the growing season. Why that is so requires a basic understanding of how grapevines grow and yield fruit and how pruning them correctly will enable you to grow a full, healthy crop of grapes each year.
Grape Pruning Basics
The only shoots or spurs that yield grapes are those that grow each spring from one-year-old canes, those that began growing the previous year. The shoots that bear grapes are called fruiting shoots. The canes they grow on are called fruiting canes. You prune grapevines to produce the optimal number of fruiting shoots and fruiting canes for the coming growing season.
Imagine that your arms are outstretched to form a T. Your body is the woody vine, called the trunk. Your outstretched arms are fruiting canes. Permanent, woody fruiting canes trained to grow horizontally on trellis wires are called cordons. Cordon-trained grapes are typically spur pruned. Grape plants with trunks that do not have cordons are cane pruned.
You select a dormant shoot every 6 to 8 inches along the cordons and prune them back to several buds. These pruned shoots are called spurs. The end of the spurs should be roughly the width of a pencil. Shoots that grew upward to the sun will bear more grapes than shoots that grew downward in the shade. The buds on these pruned spurs should grow into fruiting shoots, yielding the maximum number of healthy grapes. No shoots should have to be removed in spring. University of California Cooperative Extension Kern County recommends spur pruning for most grapevines grown in the backyard.
Cane pruning is typically reserved for "Thompson" seedless grapes and other varieties with basal buds that do not produce fruit. A basal bud grows at the base of a shoot. You remove all but two to four fruiting canes on each woody trunk to a point where they each have about 15 buds. The selected canes should be roughly from 3/8 to 5/8 inch wide. Fruiting canes on table grape varieties should have a total of 50 to 80 buds. Fruiting canes on wine grape varieties should have a total of 20 to 30 buds.
- Texas A&M University: Pruning Grapevines
- Oregon State University Extension Service: Prune Your Grapes Heavily in Winter
- Ohio State University Extension: Basic Principles of Pruning Backyard Grapevines
- University of California Agriculture and Natural Resources: Pruning Grapevines
- University of California Cooperative Extension Kern County: Homeowner’s Guide to Pruning Backyard Grapevines
- Purdue University: Principles and Practice of Pruning Grapevines
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