Next Sunday spring will officially arrive. It is common knowledge that late winter or early spring is time to prune fruit trees. So armed with that knowledge, pruners and a saw, you head out to get your fruit trees ready for another season. As you stand looking over the trees, you wonder just how you are supposed to know which branches to remove.
This article will answer some of those questions, but for detailed information and a demonstration on pruning, attend all or part of the free pruning seminar next week sponsored by the USU Cooperative Extension Service. It is open to the public. Larry Sagers, regional horticulturist for Extension and the co-host of the KSL Greenhouse Show on Saturday mornings, will teach a pruning class Wednesday, March 23, at 7 p.m. at the USU Extension office auditorium, 151 North Main in Tooele. He will follow up the class with demonstrations of pruning various trees and shrubs on Friday, March 25 at 10 a.m. and 2 p.m. There is no charge for this class and everyone is invited. The morning session will be at the home of Ray Beck, 156 S. 100 W., Tooele.
The afternoon session will be at the home of Gary Fawson, 187 Waterhole Way, Grantsville. Done correctly, pruning will invigorate fruit trees and make them more productive and stronger. It also removes plant parts damaged by diseases or insects. Training your fruit trees is essential if you intend to grow high quality fruit in the backyard orchard. Properly trained trees have strong trunks and branches that support the fruit and will not break down with the snow or wind. They also collect the sunlight to nurture the plant and make sweet, large, tasty fruit.
To achieve those objectives the answer to how to prune a tree is “It depends on the tree.” Understanding a little about tree physiology helps clarify the procedures. Pomes are fruits with multiple seeds like apples and pears.
Fruits form on a two-year cycle. The first year, buds form and the second year the fruits differentiate. The fruits form on their stems attached to the end of a spur — a separate small woody stem attached to the branch. Those spurs continue to grow longer and produce fruit every year. Protect those spurs for best fruit production. Spur-type apple trees develop long limbs with only a few side branches and many fruiting spurs. Peaches apricots and other stone fruits grow on stems that are attached to the sides of branches. They form on oneyear- old wood.
In terms of pruning, this means encouraging and developing spurs on pome fruits and constantly cutting stone fruit trees to keep an adequate area of prime, new fruit producing wood.
Fruit trees, if left unpruned become tall, dense and unmanageable. Pruning fruit trees is always a matter of encouraging fruit production and keeping the tree size and shape within bounds to facilitate harvest. Pruning and shaping should begin the day the tree is planted and continue annually through their lives. If they are not properly shaped when they are young or if they are left unpruned for several years, they develop too many branches, grow too tall, develop lateral branches that are too long, and the tree grows dense so that sunlight doesn’t penetrate the interior of the tree.
All fruit trees, regardless of their training system, need certain basic pruning care. Begin by cleaning up the tree. Remove dead, diseased and broken branches whenever they occur.
Dead branches provide an avenue for insects and diseases to enter to cause further problems. Remove water sprouts (long, fast-growing branches that go straight up with wide distances between the nodes) and suckers (similar branches that extend up from the root.) Remove branches that rub or cross each other and weak, drooping and unproductive branches. Let in light by removing branches that compete with other branches for light, shade the center of the tree, or grow back in toward the center of the tree.
Make all pruning cuts next to the collar (the wide portion of the branch that spreads where it attaches to the trunk or other branches). Do not leave a stub or cut into the collar because it will not heal over properly. By their natures, some trees need more extensive pruning than others do. Some respond best to one system of pruning and others flourish under a different method.
The modified leader system is ideal for semi-dwarf or spur-type apples and also pear trees. Such a tree has one main trunk with tiers of branches spaced vertically along it. To train a tree to this system, cut the newly planted tree back to 30 inches high — just above a healthy side branch or just above a bud. Watch to be sure that one central branch grows up as a new trunk through the season. The lowest tier of branches should be 24 to 48 inches from the ground, extending out in four directions as nearly perpendicular to each other as possible. The next tier of scaffold branches should be spaced 18 to 24 inches apart vertically up the trunk. They should also come out in four directions perpendicular to one another, but ideally, they should be spaced between the lower tiers if possible. Continue developing tiers until the tree reaches the desired height. Generally, the tree will have about three layers of branches and will be 15 feet high. The branches should form 40 to 90 degree angles with the trunk. If the trunk angle is too narrow, put braces between the branch and the trunk for a season to widen the angle.
The number and spacing of the branches and the height of the leader varies with the type of tree — semi-dwarf, dwarf, apple, cherry, pear or plum.
The open center system is ideal for peach trees. The trunk extends about 18 to 30 inches high. From there develop three or four scaffold branches, all at or near the same height on the trunk and spaced as uniformly as possible from each other around the tree. Keep these about the same size by pruning.
Scaffold branches form a crotch angle of 40 to 90 degrees with the trunk. Do not let the branches develop sharp angles with the vertical portion of the trunk or they will be weak and split under a heavy fruit or snow load. The idea of an open center tree is to keep all of the extra wood out of the center of the tree. Prune so that the branches point to the outside of the growing area so the trees spreads out rather than growing upright.
Keep the open center, or vase tree, low for easy picking, spraying and pruning, and the open center allows light to the center for forming and coloring fruit.
If you have a tree that was already shaped to a different system, than outlined for a particular tree type above, work with the established system — do not try to change it.
In general, peaches and nectarines require the most pruning, followed by Japanese plums, apples, apricots, sour cherries, European plums and sweet cherries. Do not prune cherries much at all. They are large trees by nature, so do not try to control growth by pruning. Pruning too heavily encourages the growth of water sprouts — long, willowy upright branches that grow straight up and do not form fruit. These trees tend to grow long, upright branches in any case. Simply prune off branches that are interfering with one another or growing too close together. Watch during the growing season and if upright sprouts grow too long, clip them back to a bud to encourage side branching.
Generally, prune pie cherries to the open center system. These trees are quite brittle and tend to grow at very narrow angles. Train the branches to wide angles while they are small.
Train apricot trees to either the open center or the modified leader system. They do not require a great deal of pruning. Because they blossom so early that spring frosts often limit fruit production, you may wish to delay pruning until after they blossom.
Tips for the week:
Buy a good quality pruner to care for trees. Poor quality tools will get out of alignment very quickly and will tear the wood rather than cut it. Quality pruners are drop forged rather than stamped out of thinner metal. Quality loppers cost more, but they are a lifetime investment if they are well cared-for.