By Nikki Phipps
(Author of The Bulb-o-licious Garden)
In addition to support, pruning grapes is a vital part of their overall health. Regular pruning is essential for controlling grape canes and producing quality fruit yields. Let’s look at how to prune grapes.
How and When to Prune a Grapevine
Grapes should be pruned during their dormancy, usually in late winter. When it comes to pruning grapes, the most common mistake people make is not pruning hard enough. Light pruning doesn’t promote adequate fruiting whereas heavy pruning provides the greatest quality of grapes.
Knowing how to prune grapes can make the difference between a good crop and a bad one. When pruning grapes, you’ll want to cut off as much of the old wood as possible. This will encourage the growth of new wood, which is where the fruit is produced.
How to Trim Grape Vines Requiring Winter Protection
While there are several ways you can trim a grapevine, all share the same basic steps for managing varieties that require winter protection. These grape varieties should be pruned into one horizontal trunk that can be easily removed from the trellis or support structure.
Prune old, neglected vines in stages. These should be pruned each year, removing all growth with exception to new fruiting canes and renewal spurs. Renewal spurs will supply the new fruit canes for the next year’s growing season.
Select a sturdy cane and cut this back 3-4 feet, leaving at least a two-bud renewal spur. This cane should be tied to a wire support or trellis. Be sure to remove all other canes. As the vine completes each growing season, you’ll cut off the old trunk just below the renewal cane.
How to Trim Grapevines Using the Kniffen Method
The easiest way to prune grape varieties that don’t require winter protection is by using the four-arm Kniffen method. This method involves using two horizontal wires to support the vine, rather than one. The bottom one is usually about 3 foot from the ground while the other about five feet.
As the grapevine grows, it is trained onto the wire(s), removing all shoots between the wires and cutting back the shoots along the lower one to only two buds. Mature vines will have about 4-6 canes with anywhere from 5-10 buds on each and 4-6 renewal spurs with two buds each.
Basic pruning of grapes is simple. If you require more extensive knowledge of pruning grapes, then further research may be needed. However, for most home gardeners, simply pruning off the old wood and making way for new fruiting wood is all that is needed for how and when to prune a grapevine.