Palmette-leader and Central-leader Tree Forms Compared for Light Distribution, Productivity, and Fruit Quality of `McIntosh' Apple Trees

Abstract

Mature `Macspur McIntosh'/MM.106 apple trees (Malus domestica Borkh.) trained to the central-leader (CL) tree form were converted to the palmette-leader (PL) tree form in 1987 by removal of east- and west-oriented scaffolds in the upper canopy. Control trees were pruned to maintain the CL form. Dormant pruning in subsequent seasons maintained either tree form. No summer pruning was done. Canopy light levels along horizontal transects 1 m above the soil and vertical transects, both through the center of the canopy, were unaffected by tree form or transect direction. Yields were significantly lower for PL trees in 1987 and 1989, while yield efficiency was reduced in PL trees in all 3 years. Fruit size, trunk cross-sectional area growth, and foliar macronutrient content were unaffected by tree form. Fruit color development in both the upper and lower halves of the canopy was not influenced by tree form during the study.