Pruning - Training Systems
The shaping and pruning of a fruit tree is not normally a random process. Instead, pruning can be guided by the training system or basic shape and orientation of the branches. Fruit trees are trained in such a way that allows sunlight to reach as many of the branches as possible. There are two commonly used training systems, the central leader and the open center, but fruit trees can also have a natural shape with no particular training.
The open center training system is used for very large apple trees, and for peach, plum, cherry and apricot trees because of their strong vigor and tall height. The limbs are trained outward from the center and at an angle which shortens tree height. Smaller branches are borne on these limbs which will bear most of the fruit. Ideally, there should be no more than five major limbs on an open center tree. Additional limbs above this number can be removed by pruning. The center of the tree canopy is kept free of branches to allow sunlight to reach the lower branches. Branches that grow into the center should be removed. A variation of this system called the multiple leader system is used for pears.
Semidwarf apple trees are typically trained as central leader trees. Dwarf apple trees can be trained using a variation of the central leader system. With this system, there is one center limb that grows vertically and bears branches arising at varying intervals along its length. If the tree has more than one branch growing vertically as a center leader, remove all but one. Large branches with an upright growth habit shade other parts of the tree, so it is best to have only one in each tree. The upper limbs should be shorter than the lower limbs so that sunlight reaches the lower branches. Limbs are typically selected for a horizontal orientation since vertical limbs are less fruitful and create more shade. Another important aspect of this system is the spacing between the upper and lower limbs. There shouldn’t be any limbs that are directly above another. In this case, one of these limbs should be removed. In a semidwarf tree, limbs should be vertically separated by a distance of four to five feet so that the upper branches are not shading the lower branches. Because of their smaller size, dwarf trees do not need as much space between upper and lower limbs. Branches that bend below a horizontal plane should be removed or cut back because they shade other branches and do not typically bear fruit.
In many cases, fruit trees have no training system, but rather a natural appearance with no imposed order. When pruning such a tree, prune out crowding and competing limbs and branches. Strive for good sunlight penetration and air circulation throughout the canopy. Remove all dead, damaged and diseased limbs and any limbs that rub against another. A wound can develop where limbs continuously rub each other. Keep in mind that branches bend downward with the weight of the fruit as the season progresses, so that small branches that rub against another in springtime may not be rubbing by late summer.