Marin IJ Articles
January 2, 2015
A famous horticulturist once said, "Of all the operations connected with horticulture, pruning, shaping and training bring the person into closest contact and sympathy with his plant."
Pruning, when properly done, strengthens rather than weakens a tree. The bottom line is that all cutting should be done for the right reasons, in the correct way and at the proper time.
Getting your newly planted fruit tree off to a good start is one of the most important reasons for pruning. Pruning in young trees trains them to become structurally sound, makes them easier to care for and ensures production of high-quality fruit. Pruning early in the life of the tree ensures that pruning wounds are small and closure is more complete minimizing the change for injury or disease.
In addition to the removal of dead, broken, diseased, dysfunctional or crossing branches, proper annual pruning promotes more even light distribution throughout the tree and the development of robust buds/flowers and a strong limb structure. Controlling the size of the tree permits easier care in maintaining and picking fruit.
In general, the optimum time of year to prune most fruits is now, during the dormant season when the leaves are off — from December until the middle of February. Because there is a risk for serious disease when apricots and cherries are pruned in the winter, pruning is done in the summer. A good rule to follow is to prune the latest-blooming trees first and the earliest-blooming last.
Within a particular fruit type, the oldest trees should be pruned first. To minimize the chance of infection, desirable cuts on twigs and small branches are made at a gentle angle about a one-fourth inch above a bud. The cut is angled so that water does not sit on the cut surface, allowing the growth of disease organisms. Prune so that the resulting wound can close easily.
Most cuts are either heading or thinning cuts. Heading cuts shorten the branch; they stimulate lush regrowth and branching below the cut. Thinning cuts remove an entire branch to a side shoot; they are used to shorten limbs, improve light penetration and direct the growth of a shoot. Horizontal branches are more fruitful. Downward bending branches lose vigor and produce only a few small fruit. Remove the part hanging down, suckers and water sprouts. Improperly trained fruit trees generally have upright branch angles, which result in serious limb breakage under a heavy fruit load.
When a tree is small, much of the pruning is corrective, such as pinching buds and redirecting branches to persuade the tree to grow into a strong, attractive shape. During the prime of its life, a tree may benefit from more corrective pruning to rejuvenate it or enhance its beauty or usefulness. In a tree's old age, prune mainly to keep it healthy and prolong its useful life.
The objective in pruning is to help shape a tree so it is aesthetically pleasing, produces quality fruit and serves well in the space it occupies. Sun-exposed branches remain fruitful and produce the largest fruit. Shaded branches eventually stop fruiting. With these considerations in mind, two training/pruning systems are used for fruit trees:
• A tree pruned to the central leader system is characterized by one main, upright trunk, referred to as the leader.
• The vase-shaped system produces large trees and is characterized by three to five major limbs, called scaffolds, coming out from the trunk.
Vase shapes provide good access to fruit from the ground, but the branches are typically more weakly attached to the tree. Central leaders have the advantage of being strong, while still allowing good access to light. However, the disadvantage of a central leader system is that the tree can grow quite tall, and therefore fruit may be out of easy reach. Thus, the central leader system is best for trees on dwarf or semi-dwarf rootstock.