In the March 6 and March 13 columns were guidelines for choosing fruit trees for our USDA Hardiness zones 7 and 8. In today’s column are guidelines for training stone fruit trees.
Pruning of fruit trees is done to train the tree to a specific growth system. The most popular stone fruits are peach, apricot, plum, nectarine and cherry.
The primary reason for pruning stone fruit trees is to open the interior to sunlight. Fruit production depends upon light in the canopy. With too little light, fewer carbohydrates are synthesized in photosynthesis resulting in fewer, smaller fruit. Opening the interior not only allows for increased light penetration but also allows for air movement. Aeration reduces the incidence of fungal pathogens like those that cause the devastating disease, brown rot.
Neglected or improperly pruned fruit trees have an upright central leader, upright branches and smaller lateral branches that easily break under a heavy fruit load.
Train stone fruit trees to the open center system, also called the open vase technique.
Training a stone fruit begins with pruning the sapling. Cut back an unbranched tree to about 30 to 40 inches above ground level. The height at which the heading cut should be made is a function of the ground equipment that will be used under the tree’s lowest scaffold branches; equipment should be able to move under the lowest limbs unobstructed. Scaffold branches become the heaviest limbs and are those that form the tree’s backbone. Buds that produce the scaffold branches appear several inches below the heading cut.
The final structure of the tree should have three or four scaffold branches located at 60- to 90-degree angles from each other like points on a compass - north, south, east, and west. Looking down from above the branches form a spiral.
From its silhouette, the shape should look like an open vase or open bowl. Young branches that will become scaffolds should be cut back by one-third or one-half; over time these branches will thicken and bear the fruit. During the growing season keep the interior open by removing small shoots that form in the center.
Prune stone fruit until just before bud break in the spring. When pruned too early in the winter months trees are susceptible to cankers. Early spring is the optimum time to prune stone fruits, ideally just before bud break.
Ellen Peffley Harp, a retired professor of horticulture at Texas Tech University, writes about gardening for several Texas newspapers.
