Grape Pruning: Three Systems
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
Spur Pruning: Two-Arm
In this system you develop two permanent arms with spurs that produce fruiting wood each year.
Spur Pruning: Head-Trained
For this system, the vine will need only a strong, vertical, 4-foot post for support.
1. Allow the vine to grow to the top of the post and cut just above that point. Tie to the post. Remove any branches below. Next year, let four or five branches grow.
2. In the winter, cut each of the branches back to two or three buds. Remove any weak branches and any on tower parts of the trunk. Buds left on spurs will produce fruiting shoots next year. You can allow more branches to develop as the vine matures so there will be more fruiting shoots each year. A mature head-trained vine can have more than seven main branches.