THE STRUCTURE OF CENTRAL LEADER TREES FOR MEDIUM-DENSITY ORCHARDS AS RELATED TO ENVIRONMENTAL CONDITIONS AND TREE VIGOR
The medium-density orchard system with central leader trees is adaptable to a wider range of natural as well as socio-economic environments and can be an important orchard system in many apple growing areas where environmental conditions are less favorable. However, central leader trees grown on relatively vigorous rootstocks tend to produce large-sized trees with proportionately large, unproductive spaces within the trees. Maintaining good light exposure to the bottom limbs should be the emphasis. In view of the depth of leaf layer in which marketable apples can be produced, the spread of the tree canopy should not exceed much more than 2m from the trunk, even at the bottom of the tree. The middle and upper lateral branches should be kept much shorter than the bottom limbs. All lateral branches including the bottom limbs should have no large side branches and they should carry fruiting branches directly. This structure is effective in keeping good light condition within the canopy and in suppressing the thickening and elongation of lateral branches. A relatively large number of such lateral branches should be grown along the central leader. As the vigorous tendency of the tree increases, the bottom limbs should be grown in a more upward direction. This structure enables the bottom limbs to be elongated without heavy heading cuts and to come into full bearing before they outgrow their allotted spaces. It also contributes to keeping them from being overgrown by the upper lateral branches. The length of the top of the central leader should be kept longer without fruiting branches to suppress lateral branches below it.
Kikuchi, T., Shiozaki, Y., Asada, T. and Arakaw, O. (1997). THE STRUCTURE OF CENTRAL LEADER TREES FOR MEDIUM-DENSITY ORCHARDS AS RELATED TO ENVIRONMENTAL CONDITIONS AND TREE VIGOR. Acta Hortic. 451, 537-542
Malus domestica, training system, light penetration, principle of continuous change