How Much Should I Prune My Grapes?

Canes to Keep

• Prune 80 to 90 percent of growth each winter after the danger of severe freezing has passed. Leave two to four fruiting canes for each plant. Only shoots that grow from 1-year-old canes will yield grapes. Fruiting canes that were exposed to light during the previous growing season will yield the most grapes. Keep fruiting canes that are 1/4 to 1/2 inch round, about the size of a pencil, and are brown almost to the tip.

Bud Pruning Formula

• You control the amount of grapes by pruning buds. Horticulturalists at Oregon State University recommend that you prune each fruiting cane back far enough to leave about 15 buds. If you’re growing wine grapes, leave 20 to 30 buds on each plant. If you’re growing table grapes, leave 50 to 80 buds for each plant.

Weight Pruning Formula

• Prune 90 percent of the growth from the previous year and weigh it or estimate its weight. Texas A&M University recommends a 20 plus 10 formula based on the estimated weight of the canes that you pruned. That means you should leave 20 buds for the first pound of canes that you prune and 10 more buds for each additional pound that you remove. Vintner Michael J. McGroarty recommends that you leave 30 buds for the first pound of wood that you prune and 10 buds for each additional pound that you remove. Mark's Fruit Crops recommends that you leave 20 buds for the first pound of pruned wood and 10 to 20 buds for each additional pound of pruned wood.

Spurs Versus Canes

• Once you decide how many buds you should leave, you have to decide whether to prune spurs or canes. Spurs are short stubs with a few buds. Canes are longer and have more buds. Prune spurs when the buds at the base of 1-year-old wood produce grapes, usually the case with wine grapes and on cultivars that grow vigorously. Prune canes on grape cultivars that do not yield well or on varieties such as Thompson seedless grapes that will not grow grapes on buds at the base of the previous year’s wood.