Flowering of Young Apple Trees following Summer Pruning1

Abstract

Abstract Axillary spurs and shoots produced in 1976 by heading back or pinching shoots did not flower in 1977 on ‘Starkrimson Delicious’ and ‘Red Prince Delicious’ apple (Malus domestica Borkh.) Similar treatments induced flower bud initiation on shoots of ‘Cortland’ when applied in 1976 and 1977 and on ‘Red Prince Delicious’ in 1977. Late June and early July treatments were more effective for inducing flower bud initiation than were treatments applied later. The year following summer pruning total bloom and fruit set were not increased and in some instances were reduced. Pruning current season shoots of ‘Red Prince Delicious’ and ‘Cortland’ to 0.5 to 1.0 cm stubs failed to induce flower bud initiation. ‘Cortland’ produced terminal flower buds on some long axillary shoots, while weak regrowth following pruning appeared necessary for formation of terminal flower buds on axillary growth of ‘Red Prince Delicious’. Heading back most shoots on vigorous ‘Cortland’ and ‘Red Prince Delicious’ trees on June 21 or later devitalized the trees in spite of regrowth, although growth was not restricted the following year. Cultivar, tree vigor, and time and type of pruning all affected amount of regrowth.