MOUNTAIN GROVE, MO – Grapes are woody vines or lianas that usually grow up trees to find sunlight. Often, they grow in the shade until they reach the top of the tree and then they will get sunlight to set flower bud for fruit production. We train our grapevines up a trellis so we can keep it in bounds and have it bear fruit that can be easily harvested. If we did not prune grapevines every year, they would scamper away from the trellis just like they grow up trees in the woods. We must continue to maintain a balance between vegetative growth and fruit production by annual pruning.
The pruning that we do in the early life of the plant actually involves training the vine to the trellis. Training takes about three years during which time we remove any fruit that is produced until the third year when we allow the vines to ripen a small crop. Once the vines are trained and mature, the vines must be pruned annually to keep fruit production in balance with vegetative vine growth. Annual pruning serves to keep fruit in the “fruiting zone” – in its place, off the ground, well exposed to sunlight, and easy to pick.
The high wire cordon system, common in Missouri, is where the old wood (trunk and cordons) are shaped like a “T” and the horizontal top of the “T” is tied to a trellis wire about 5 or 6 feet horizontally above the ground. The fruiting wood is maintained as “spurs” on the cordons – shortened canes with buds. Home growers may choose a different system or they may want to train their grapevine over an arbor or pergola. However the pruning concept is the same – to evenly space the buds throughout the fruiting zone.
Keep in mind that the cane or spur is a different color, has visible buds, is smooth and does not have shredded bark like the old wood. Be sure you choose canes or spurs that are about pencil size in diameter for fruit production. When you prune or cut the new wood, look at the cut and see if the exposed inside of the cane is green. If it is brown all the way through, it is dead and should be pruned away.
Prune the fruiting wood back to spurs or canes (depending on your training system). Whether you leave the fruiting wood as long canes or short spurs, leave from four to six buds for every foot of space you have on the trellis wire or arbor (the lower number if you have a smaller vine without much new wood and six if you have a larger vine with a lot of new wood). Once you have pruned your fruit-producing wood in the “fruiting zone” and have evenly spaced the remaining buds, remove unnecessary suckers or shoots growing from the trunk. Also remove the tendrils that have attached themselves to the trunks, cordons and wire.
It is best to wait until late winter to prune – February or March – if you have only a few vines. You may also want to mark your calendars for our Pruning Workshop on Saturday morning March 9 at Mountain Grove. The workshop will be held outdoors in the Pavilion on the west side of Highway 95. Dress for the weather and bring your pruning tools and safety glasses.
Direct comments or questions concerning this column to Marilyn Odneal via email at MarilynOdneal@missouristate.edu; write to Missouri State Fruit Experiment Station, 9740 Red Spring Road, Mountain Grove, Mo. 65711; or call (417) 547-7500. Visit our Web site at http://mtngrv.missouristate.edu.