Tips for Pruning Grapes in the Backyard Garden

Grapes are a wonderful addition to the home garden. With proper care and pruning, they are long-lived and productive plants. Pruning can be intimidating when standing in front of a mass of tangled grape vines and wondering what to do with them. It can be a scary experience for the novice home gardener or even for the more experienced pruner. It should not be.

The goals of pruning are to obtain maximum yields of high-quality grapes and provide adequate vegetative growth for the following season. Perhaps just as important, dormant pruning is an opportunity to remove dead, diseased and broken canes. Knowing a few rules of thumb will give the home gardener a fun learning experience:

• The buds formed on wood of the previous season’s growth are fruitful buds.
• Renewal spurs give rise to  vigorous shoots that will be retained for fruiting canes the following year.
• Pruning regulates both vegetative growth and yield of the harvestable fruit in a grapevine.

When to Prune

It is necessary to prune every year. Pruning is done during winter, while the plant is dormant. The later in the dormant season that you prune, the later new growth will begin in the spring. In cold weather the frozen wood is brittle and easily broken. Pruning in temperatures as low  as -10°F to -15°F may result in injury to the wood and buds of most grape varieties, therefore it is advisable to not prune until late winter or early spring. The best time to prune is when the buds start looking plump, but before they swell rapidly toward bud break.

Proper Method to Prune Grapevines

Pruning is done to replace the fruiting wood and requires removal of between 80 and 90% of the previous year’s growth. Limiting the number of shoots is important for good cluster size, root balance, and preparation for winter. The most common mistake is not pruning hard enough. Light pruning doesn’t promote adequate fruiting whereas heavy pruning provides the greatest quality of grapes. When pruning grapes, you’ll want to cut off as much of the old fruiting wood as possible. This will encourage the growth of new wood, which is where the fruit is produced.

Some things you must keep in mind are:

• The fruit is borne on shoots rising from one-year-old wood, (i.e. previous season’s growth).
• The most productive canes are about pencil thickness (1/4 inch to 1/3 inch) and have an internodal length of five to eight inches between the nodes or buds.
• Typically, leave canes that are 8 to 16 buds in length. Thin canes should carry fewer buds than thicker canes.
• To keep the fruiting wood close to the main trunk, leave one or two renewal spurs on or near each arm. (Cut back to short spurs leaving one to four buds).
• Prune the vine so you will maintain a balance between vegetative growth and fruit production. When a vine is under-pruned, (too many buds left) the vine will produce many clusters of small grapes that may fail to ripen properly. If the vine is over-pruned, (too few buds left) the yield will be low and the vegetative growth excessive.
• If you are not sure how many buds to retain it is much better to prune more severely than to prune too little. Leave fewer buds, especially if the vine is a weak grower. If the vine has been very vigorous, retain more buds.

Methods of Pruning and Training

There are two basic systems of pruning: cane pruning and spur pruning.  For an illustration, see cane and spur pruning.

Cane Pruning: Commonly used for the Concord and other American varieties that are planted in home gardens. In a cane pruned system, almost all of last years fruiting canes are completely removed from the trunks leaving only two of the last years fruiting canes to provide buds to produce new fruiting canes and a renewal spur, originating close to the trunk, is kept to grow next year’s fruiting cane.

Spur Pruning: In a spur pruned system, the permanent trunk and semi-permanent cordons (arms of the grapevine) are left from year to year. Along each cordon , multiple fruiting canes grow from spurs (two to three buds) spaced every 4 to 6 inches along the cordon. Next season these fruiting canes will be pruned down to the cordon leaving spurs with two to three buds for new canes and fruit production.

For more training system options see Pruning Grapes in Home Fruit Plantings.

Resources

Video: Grapevine Cane and Spur Pruning Fundamentals

Cox, J. 1999. From Vines to Wines: The Complete Guide to Growing Grapes and Making Your Own Wine. Storey Books.

Winkler, A. J., et.al. 1974. General Viticulture. University of California Press.