Introduction

Apples are the most common fruit tree planted in Wisconsin. In addition to providing fruit, apple trees can be a pleasing addition to the home landscape. However, unlike most shade trees, apple trees require annual training and pruning from the time of planting to produce an attractive and productive tree.

Proper training and pruning are also a valuable part of an effective pest management program. Pruning to open up the canopy improves air flow, reducing some disease problems. An open canopy also allows better access for managing insect pests.

Training and pruning cannot compensate entirely for poor horticultural factors such as poorly matched scions (the above-ground portion of the tree) and rootstocks. For example, if a strong spur-type scion, which produces little vegetative growth, is grafted to a dwarfing rootstock, the resulting tree will “runt out.” That is, it will produce little new growth and small fruit, regardless of how it is pruned. On the other hand, a vigorous scion on a standard or semi-dwarf rootstock planted in a fertile soil will become a large, unmanageable tree that cannot be pruned into submission.

Pruning Apple Trees to Maximize Healthy Fruit Production

Pruning vs. Training Apple Trees

Pruning should be used to open “windows” to allow light to penetrate throughout the tree. When all of the leaves are exposed to more light, the tree is able to produce higher quality fruit. However, be careful not to remove too many branches, as pruning can stimulate excess regrowth. When a portion of a branch is removed, the tree responds by producing new growth. Often three or four branches will grow where only one grew before, resulting in a “grow and cut” cycle. While excess regrowth can be minimized through proper cuts and by cutting into older wood where possible, it cannot be entirely avoided.

Limb Positioning Techniques

Spreading

This technique uses objects such as toothpicks, clothespins, or short sticks to push branches towards a horizontal position. For very young trees or for young succulent growth in older trees round wooden toothpicks or spring-type clothespins work well (figure 3).

Insert spreaders in mid- to late June, when young branches are 3–6 inches long. If using toothpicks, gently push them into the soft bark of the limb and trunk to hold them in place. For clothespins, place the gripping end on the trunk and push the open side against the small limb to force it towards horizontal.

For older trees and branches, you can use wooden, metal, or plastic spreaders to push branches into position. Wooden spreaders (figure 4) can be made or purchased in any length needed. To make a wooden spreader, notch the ends or, for larger stock, drive small nails into each end of the spreader then cut off the heads of the nails using heavy pliers to create a sharp surface that will hold in the tender bark.

Tying

Weighting

Timing for Limb Positioning

The best time to position younger branches is in June or when they are 3–6 inches long. Positioning older branches is less time dependent. Most growers position branches when they dormant prune, others position limbs in late spring to early summer. Limbs positioned towards horizontal in spring to very early summer will initiate flower buds for the following year, not the current year. Weak branches that are hanging from the weight of fruit should be tied up as early as possible.

Training Young Apple Trees

The objective in training a young tree is to develop a structure that will provide a strong framework to support fruit production. The top of the tree should be smaller and narrower than the bottom of the tree. This shape prevents the top of the tree from shading the bottom of the tree. The central leader system (illustrated above) produces a vertical central leader or main stem and strong, properly spaced scaffold limbs. This system is easy to prune and provides optimum production potential.

Over the years, you will train two to three tiers of scaffold branches. These branches will form the central framework of the tree and should grow at a wide angle from the leader.

At Planting

If you plant an unbranched whip tree, cut off the top leaving the tree 30–45 inches tall. Side branches will grow from the whip the first year. New branches will grow just below this cut. You control the location (height) of the new limbs by the height of the cut. If you’ve purchased branched trees, remove only limbs that are broken, damaged, poorly positioned, or that are too low on the trunk.

Year 1

During the first summer, choose four or five good branches for the lowest tier of scaffolds. The lowest scaffold limb should be at least 24 inches above ground and can be as high as 36 inches in a landscape where flowers or bushes under the trees are desired. Limbs growing closer to the ground make it difficult to work around the tree. Select well-spaced branches growing within about 18 inches of the lowest branch that are growing neither exactly opposite nor directly above one another. For the first dormant pruning in late spring, remove weak or poorly positioned limbs that will not become scaffolds.

Years 2-3

After two or three years, select a second tier of scaffold limbs. Again, choose or create branches with wide crotch angles. The lowest branch of the second tier should be at least 24 inches above the top branch of the lower tier. This 24-inch gap allows light to penetrate into the canopy and to strike the lower tier of branches. The upper branches must be kept shorter than the lower branches to keep them from being shaded. This will create a “Christmas tree” shape. For dwarf trees, two tiers will be sufficient; for semi-dwarf trees, repeat the process to create a third set of scaffolds near the top of the tree.

Yearly Maintenance

Remove all dead and broken branches annually, as well as suckers, water sprouts, and branches forming narrow angles. By the fifth year, trees should be well established with two tiers of scaffolds. Spurs should be developing throughout the tree to provide annual fruiting.

Pruning Bearing (Mature) Apple Trees

The objective of pruning bearing trees is to maintain maximum production of high-quality fruit on a continuing basis. Properly trained trees require little pruning but must still be pruned annually. Limit pruning of bearing apple trees to removal of weak, unproductive branches to improve light penetration and distribution, reduce tree height, and improve spray coverage.

As trees grow older, you may need to make more thinning cuts. Don’t let the upper branches grow longer than the lower branches. Long upper branches shade lower branches and reduce productivity. If necessary, prune upper branches into 2-year-old or older wood to keep them shorter than lower branches. Thin out weak, unproductive branches, and keep the tree “open” for good light penetration. In the top of the tree, branches can be cut back to the trunk leaving a short stub (about ¹⁄₂ inch long) on the bottom of the cut (figure 7). A new branch will often grow from the base of the stub.

If an older tree is too tall for convenient spraying and harvesting, more drastic steps must be taken. To lower the height of a tree, completely remove one or two of the tallest growing limbs. Make the cut where the limb joins the trunk. When you prune drastically, you must greatly reduce other pruning in the tree that year. Over-pruning will stimulate too much growth and lower fruit production. Spread out extensive renovation pruning over 2–3 years.

Trees that have not been managed or pruned for several years are generally not reclaimable. The large cuts that are required to allow light and air into the canopy will produce much vegetative vigor that will require even more pruning, creating a vicious cycle. You will be better off to remove the old trees and replace them with young trees on dwarfing rootstocks.

Pruning Procedure

To prune apple trees efficiently, follow these steps:

• Cut off water sprouts growing on the trunk and scaffold limbs. Occasionally, a water sprout may be left to fill in an open area.
• Remove broken and diseased branches.
• Remove the weakest of crossing or closely growing parallel limbs.
• Remove all limbs or spurs growing downwards.
• If the tree needs more branch thinning, remove weak, spindly branches first. Remove dense or long growth from the upper portions of the tree which shade lower limbs. Limbs growing within arm’s reach are easier to harvest and spray.

Remember these tips when pruning apple trees

• Light is required for quality fruit.
• Prune during the dormant period, late winter or early spring. March and April are best.
• Use tools made specifically for pruning and keep them sharp and clean.
• Make all cuts smooth and close. Leave the collar but not a stub (except for branch renewal).
• On cultivars that bear heaviest on alternate years, do heavy pruning just before the bearing season.