Blackberries grow as vigorous vines that require heavy pruning at proper times. Prune all canes that bore fruit immediately after harvest. If grown unsupported, the new canes can be trimmed to a height of 2-3 feet. These should be headed back in early Spring to leave about 1 foot of bearing wood. Raspberries grow and bear fruit similar to blackberries.
Red varieties tend to sucker when headed back rather than make lateral growth.
Black-fruited varieties tend to send out more lateral shoots when headed. Heading back should be done early in the growing season to about 2-2.5 feet. The laterals should then be pruned back to 5-6 inches during the dormant pruning. Leaving longer laterals may result in small berries. Fruiting canes of both types should be removed immediately after harvest.