Erect the trellis before planting or as soon as possible after planting. Use 8 foot treated posts 3 to 4 inches in diameter. Set the posts 2 feet in the ground and 20 feet apart. End posts should be 8 feet apart, 3 feet in the ground and braced. This bracing system is commonly used in fencing. A one or two wire vertical trellis can be used. Use 9 or 11 gauge smooth, galvanized wire stretched horizontally on firmly set posts.
During the first season, the primary objective for grape vine growth is the development of a healthy root system and a straight trunk. After setting the vine, prune to one stem and cut this stem back to two or three buds. When new growth begins and the first shoots from the two-bud cane reach 6 to 10 inches in length, select the most vigorous and prune off the others. Tie the shoot gently to a training stake (tomato or bamboo stake) several times during the first season. An alternative is to tie the shoot tip to the upper wire with a string and allow the shoot to weave its way up to the wire. Pinch lateral shoots back to the leaf growing on the main shoot. This allows the main shoot to grow more rapidly, possibly saving as much as a year in establishing a healthy vine.
For best yields, quality and disease control, grapes should be pruned every year. A vine stores a limited amount of food in its roots, trunk, and canes during the winter. In the spring, food reserves are directed to buds for shoot growth. If left unpruned, those reserves must be distributed to numerous buds. As a results, the vine will produce a lot of weak shoots and small, poorly ripened fruit clusters. Pruning reduces the number of buds so the food reserves are concentrated in those that remain. Grapes are borne on current seasons’ wood that grows from buds formed on last seasons’ growth.
This is one of the most popular training systems for bunch grapes. It gives good production, requires little summer pruning, and is adapted to moderately vigorous cultivars. The trellis consists of two wires.
After the shoot reaches the top of the trellis, cut the tip off and tie the cane to the top wire. As soon as the new shoots begin to grow the following spring (year two), remove all but four of the strongest canes near each wire. The following winter (year three after planting) select the four best canes near each wire and remove the rest. Select the two strongest canes (one for each wire) and cut them back leaving five buds. Tie one cane along the wire in each direction. These four canes will become the main arms of the vine. Cut the remaining four canes to stubs containing two buds. These will be the renewal spurs.
In the winter of the following year (fourth year after planting), remove each arm and replace it with the strongest cane that grew from each renewal spur. Cut the selected canes back to ten buds and tie to the wire (one in each direction). These canes will become the new arms. Cut back (to two buds) an additional cane near each new arm to form renewal spurs. Each winter thereafter, replace the arms with canes from the renewal spurs, and leave new renewal spurs. All other canes are removed.
High-wire cordon system
This system is often used with American bunch grapes. The initial training of the trunk is the same as described above. With this system cordons are trained along the one wire at the top of the trellis.
After the shoot reaches the top of the trellis, cut off the tip just above the wire. In the spring (year two), select two of the strongest shoots to train along the wire in each direction. All other shoots are removed. Tie the shoots along the wire as they grow. In the winter (year three), remove competing shoots to the two main canes. Shorten the main canes to 5 feet. In the winter of the following year (fourth year), shorten each cane that has arisen from each cordon to two buds. These are called fruiting spurs. Select eight to fifteen spurs on each cordon and prune off the rest. Spurs should be spaced 3 to 8 inches apart. The more vigorous the vine, the more spurs you can leave.
© Erv Evans, Consumer