Composed by trellis wires, woody canes called cordons grow laterally from the trunk of the grape plant of the genus Vitus. Depending on the species, grape-bearing canes either trail downward or develop from horizontal cordons. Species with canes that naturally trail down are best supported on the top wire of what are called high-cordon trellises. People who have canes that naturally develop upwards are best developed on low-cordon trellises. Grapes can be grown in U.S. Department of Agriculture plant hardiness zones 2 through 10.
High-Cordon Trellis Species
Grape-bearing canes of native American grapes containing Concord and other bunch grape varieties of Vitis labrusca and muscat grapes (V. rotundifolia) trail downward. This trailing habit makes them acceptable for a cordon growing on a trellis wire strung from 4 to 6 ft above the ground. This really is really a high-cordon trellis. Grape-bearing canes from European wine grapes (V. vinefera) are inclined to develop upward. Their cordons are best grown on wires strung 2 to 3 feet above the ground and their grape-bearings canes trained to develop up to a top cable. All these are low-cordon trellises.
Fundamental High-Cordon Designs
Although construction details fluctuate, a basic single high-cordon trellis consists of poles at least 3 inches wide and 5 1/2 feet long sunk into the ground 1 1/2 feet deep and 20 feet apart . All these are anchored by end poles which are at least 4 inches broad and sloping 2 1/2 feet deep. The grapes are planted 10 feet apart and cordons are trained to develop laterally on No. 9 cable on top. This design leaves the very best cordon 4 feet above the ground. Other high-cordon designs call for the top trellis wire to be up to 6 ft above the ground. In case the top wire is 4 ft above the ground, then a double high-cordon trellis has an extra No. 9 cable stretched between the poles 3 feet from the ground. The lower cable is moved upwards in the event the top wire is higher. A double-curtain high-cordon trellis includes a 4-feet-long 2-by-4s secured on top of each article forming a “T.” No. 9 cable is stretched out of both ends of the “T.”
Training Vines on High-Cordon Trellises
In the conclusion of the first growing season after planting, vigorous canes are selected and the rest are eliminated. The vigorous canes are secured into the upper wire of the trellis in their next year. If it is a double high-cordon trellis, less vigorous canes are attached to the lower cord . These canes will thicken, becoming trunks. When the plants are inactive prior to the next growing season, a vigorous trunk should reach both or one trellis wires. Both best canes growing outward on every trellis cable are shortened, each with two to four buds. These buds will develop grape-bearing shoots called spurs.
High-cordon native grapes are pruned annually to make harvesting easier and to make sure annual harvests. All one-year-old spurs on dormant canes are cut back to 4 to 5 inches long. These can yield grapes in the coming season. Developing clusters of spurs must be thinned after the next growing season, leaving at least 6 inches between spurs. As spurs grow older, they become woody canes that cease bearing grapes but develop grape-bearing spurs.