Pruning is generally not needed until the third year after planting if growth is normal. In early spring before growth begins, remove dead or injured branches, short or stubby branches near the ground, and old stems of low vigor. Leave vigorous branches unpruned (Figure M-21.). After the plants are five to seven years old, it is important to remove some of the old canes each year. In general, it is a good idea to maintain five to seven older canes, as well as one or two new canes. Once these numbers are attained, one or two older canes can be removed annually, and one or two new canes can be left to replace it. This practice allows vigorous younger canes to develop and facilitates complete bush renewal over a five-to seven-year period.
Pruning also increases the size of the berries and promotes earlier ripening. If the plants have formed an unusually heavy load of fruit buds, the tips of the fruiting branches can be cut back to leave four to six fruit buds. Although this reduces yields slightly, the berries are appreciably larger. The fruit buds are easily distinguished in the spring because they are large, round, plump buds. Leaf buds are smaller, thinner, and sharply pointed.
Under good growing conditions, vigorous shoots may rapidly develop and grow several feet tall. If the tips are cut back before August 1, the canes usually develop strong lateral branches that bear fruit the following spring. When the shoot is four to five feet high, three or four inches should be removed.