Growth and cropping of young apple trees as affected by heading and support of the central leader

'Delicious', 'Golden Delicious', and 'York' apple trees (Malus xdomestica Borkh.) on dwarfing rootstocks were planted in 1988. For 7 years starting in 1989, the central leaders of trees of each cultivar were subjected to a 2 x 2 factorial arrangement of heading vs. not heading and supporting vs. not supporting. Support consisted of tying the leader to a conduit to 2.1 m; heading was the annual removal of one-half of the previous season's growth from the central leader. In general, tree height was suppressed by heading and increased by support. The only effect of treatment on trunk cross-sectional area (TCA) was in 'Golden Delicious', in which support reduced TCA. Heading depressed cumulative fruit numbers in both 'Delicious' and 'Golden Delicious', while support had no effect. There was a consistent trend toward decreased cumulative fruit mass in headed trees.