Grape Pruning: Three Systems
By: National Gardening Association Editors
Grapes must be pruned every year to keep producing because once a cane has fruited, it doesn't fruit again. Fruits form only on buds that arise from the previous season's growth. Which pruning method you choose depends on the type of grape and variety you have and which seems convenient and efficient to you. For American grapes, the most widespread system is the Four-Arm Kniffen System. For the vigorous muscadine grapes grown in the South, a two-arm version of-the Kniffen System prevents excessive leaf shade.
European wine grapes are generally trained to have two permanent arms and are spur pruned. If you have only a few vines and don't want to put up a wire trellis, you can head-train European grapes instead.
Pruning is done once a year-after the coldest part of the winter. Be sure to cut back to firm, live wood; the tips are often killed back. Muscadines are usually pruned after the first severe frost in the fall.
Training the Vine
The first few years are the same for the basic systems, the goal being to produce a strong root system and trunk. Here are the steps:
1.When planting, cut the vine back to two or three buds. It's a good idea to place trellis stakes or posts by the vine at this time; the wire can be put up later.
2.Early in the first summer, pick out the strongest growing cane and let that one grow. As it gets taller, let several side shoots develop off the main one where you intend to place horizontal supports.
3. The following winter or early spring, prune back all canes as shown. Leave three buds on each of two or four lateral spurs (depending on how many arms you want). Put up wire supports.
4. The second summer, tie the side shoots to the wires as they grow. Remove flower clusters - you don't want the vine to fruit yet. Also remove shoots from all buds except those on the spurs.
Four-Arm Kniffen System
Choose four healthy, well-spaced arms to train on the wire for fruit production. If they are very long, trim back to ten buds. Choose four more canes for renewal spurs; cut these back to two buds. Remove all other canes. The following summer, the buds on the fruiting canes will grow into long shoots, each bearing two to three bunches of grapes. The buds on the renewal spurs will also produce shoots; if they are vigorous, let them fruit. If not, remove their fruiting clusters.
Remove the canes that fruited and choose one replacement from each renewal spur to tie to the wires. Trim to ten buds. Cut back another four canes to form renewal spurs. Your vine should now look approximately as it did a year ago. Repeat each year.