Green Industry Resources
Hort Update- Seasonal Information for the Green Industry
Pruning Fruit Trees
Productive fruit trees with an abundance of high quality fruit don't just happen. They result from good cultural practices, including pruning. However, fruit tree pruning is often neglected either due to a lack of pruning skills and knowledge, or a fear that the tree will be damaged or killed by incorrect pruning.
Goals of Pruning
The goals of fruit tree pruning are many, including 1) to obtain maximum light exposure for both leaves and fruit; 2) provide uniform distribution of fruiting wood along the scaffold branches; 3) control the size and vigor of the tree; 4) reduce limb breakage due to excessively heavy fruit loads; and 5) produce high quality fruit of good size. The major requirement of backyard gardeners is to have a tree small enough to spray and harvest easily. Pruning, combine with the use of dwarf fruit trees will help accomplish this goal.
When to Prune
Most fruit tree pruning is done during the dormant season when no leaves are on the tree. Cultivars or varieties of trees susceptible to winter injury are pruned in late spring before growth begins, rather than in January or February. Regardless of the cultivar grown, do not prune any tree before January or winter injury will occur. Besides dormant pruning, you may prune at planting; during July and August to restrict growth; to remove water sprouts; and to remove diseased or damaged wood. Once the basic structure of a fruit tree is developed, avoid pruning until fruiting occurs.
Fruit Tree Training Systems
There are many training systems for fruit trees, and each system has its own advantages and disadvantages. For homeowners, the modified leader system is the most versatile and the easiest to learn. Any fruit tree, whether standard sized or dwarf, can be trained to the modified leader system. In training fruit trees remember these two basic concepts: 1) excess pruning delays fruiting; and 2) branches spread to a 45-55 degree angle with the main trunk are stronger, and produce more fruit than branches with narrower branch-trunk angles.
Working with Unbranched One-Year Trees, or 'Whips'
Unbranched, one-year old fruit trees are often called 'whips', because they have a single straight trunk with no side branches and resemble a riding whip. After planting a new whip, cut the top of the trunk back to encourage buds low on the trunk to sprout and develop. This results in a tree with branches low enough for easy harvesting. Head the whip back to the following height: standard trees, 44"; semi-dwarf trees, 36-40"; and dwarf trees, 29-30".
If the tree has side branches at planting, then completely remove any branches that form narrow angles (less than 45 degrees) with the trunk. Measure the vertical distance between branches on the main trunk and remove them as necessary to achieve at least a 6" vertical spacing. Branches should also be spaced evenly around the trunk, like the spokes of a wheel. Finally, head back or shorten any remaining branches to about half their length by making a slanted cut just above an outward facing bud. Assuming the tree is planted in spring, after completing this initial pruning required at planting, the tree will not be pruned again until the following March.
Selecting Scaffold Branches
The lowest scaffold branch should be 20-24 inches above the ground, so remove any lower branches or shoots from the trunk. Choose the most vigorous upright-growing branch at the top of the tree to become the central leader. Among the remaining branches, remove those that form narrow angles, less than 45 degrees, with the trunk. Select for permanent scaffold branches 2 or 3 well placed branches that are spaced evenly around the trunk, like the spokes of a wheel, and are vertically spaced at least 6 inches apart. Remove all remaining shoots or branches. Apply branch spreaders to the scaffold shoots if needed to widen the trunk-branch angle. The central leader shoot should be two times as tall as the longest side shoot, so prune any long lateral branches back so that they are a foot shorter than the tip of the central leader when held in an upright position.
Second Year Pruning
During the second dormant season following planting, choose 2 or 3 additional scaffold branches at the top of the tree. Maintain the dominance of the central leader shoot by again cutting by any excessively long lateral branches. Secondary shoots may have started to develop on the main scaffold branches. Treat each of the main scaffold branches as a small tree, in regards to choosing secondary scaffold branches. Don't allow the secondary shoots, or laterals, of the scaffold branches to compete with the leader of that branch; so head back any extra long secondary lateral branches. Also, don't prune out the short fruiting branches known as spurs.
Prune the tree as little as possible in the next few years prior to fruit bearing. Excessive pruning will delay bearing, and result in fewer and smaller fruits in the first few years of production. Maintain the dominance of the central leader and upper branches by heading back long, lower laterals. Likewise, do not let the upper branches overgrow and shade the lower portion of the tree. Remove suckers and dead, diseased or damaged branches as needed. Remove branches growing toward the center of the tree, and the weakest of crossing or closely parallel branches.
When pruning, use tools made for the purpose and keep them sharp and clean. To disinfect pruning tools, use either a 70% denatured alcohol solution, or household bleach at one part bleach to nine parts water. Either use a sponge or dip the equipment into these solutions between cuts.