Train semitrailing blackberries to trellises (Figure 1A). The erect blackberry varieties do not require support if the tops of new canes are pruned during the summer to keep growth below 3 to 4 ft. Erect blackberries that are not topped may be trained to a one-wire trellis (Figure 1 B).
Figure 1. (A) Train trailing plants to a two-wire trellis. (B) Train erect blackberry plants to a one-wire trellis.
Construct the blackberry trellis by stretching a wire between posts set 20 ft apart in the row. For erect blackberries, use one wire attached to the post about 30 inches from the ground. For semi-trailing blackberries, use two wires at heights of 3 ft and 5 ft from the ground.
Erect blackberries, such as Cherokee and Cheyenne, require pruning out of the root suckers that arise from the crown. During the growing season, it is desirable to allow root suckers to develop to about a 12-inch-wide row. Any growth beyond this should be eliminated.
When the new shoots of erect blackberries reach 30 to 36 inches in height, cut off the tips. This will force branching lower on the canes and will cause the canes to thicken, making them better able to support a heavy fruit crop. During the winter, prune the laterals to 12 to 14 inches for convenient harvesting and larger berries. In late winter, remove any remaining dead or weak wood. Leave healthy, vigorous canes spaced at 6 canes per linear ft. (Figure 2).
Figure 2. An erect blackberry plant (A) before pruning and (B) after pruning.
As soon as the last fruit has been picked in summer, cut all the old canes and burn them. This is also a good time to tip prune and thin new shoots.
Semi-trailing blackberries should be trained to the trellis described above with a soft string.
Generally, only a small crop of fruit is produced in the first season. If growth is poor during this first season, cut the canes back to several inches in late winter to force development of sturdier, more fruitful canes. In the second and succeeding years, shoot growth is more vigorous and upright. Tie these new shoots to the trellis when they reach a length of 4 to 6 ft.
Some growers prefer to wait until harvest is over and old canes have been removed before tying new shoots to the wires. Pruning the old canes is critical to the prevention of disease. After harvest, prune damaged or weak canes, leaving 4 to 8 new shoots. Tie these canes to the trellis in a fan shape (do not bunch them). In the spring before growth starts, prune any laterals back to 12 inches to encourage larger fruit.
Published by the North Carolina Cooperative Extension Service