Pruning Fruit Trees
If there's one group of plants that demands regular and careful pruning, it's deciduous fruit trees. Taste the sweetness of a perfectly ripe pear or apricot: That sweetness represents energy. Producing luscious fruits demands lots of energy, which comes from the sun, and one goal of pruning is to help all the limbs on your tree bask in as much sunshine as possible.
Pruning also has other benefits. It's the way to strike a balance between shoot growth and fruit production, so important in ensuring that your tree bears the largest and tastiest fruits year after year. And keeping branches open to light and air also speeds drying of leaves and fruits, decreasing diseases, and allows sprays to penetrate if spraying is needed.
Young Trees: Prune for Form
The first years a fruit tree is in the ground are important to its future performance. It's then that the tree should form its permanent framework. Your goal is to help your tree produce branches that are strong enough to support their future loads of fruit, and to develop branches that won't cross or shade each other. Centuries of fruit growing have spawned many different tree forms, but three predominate: open center, central leader, and modified central leader. The ideal form for a particular tree depends not only on your preferences, but also on the plant's natural growth habit.
The tree's main stem or stems is called a leader, a continuation of the trunk. A central-leader tree has a leader with branches growing off it; these branches are shorter near the top of the tree. The open-center tree has a vase shape made up of three or four leaders growing off the trunk in an outward and upward direction. The modified-central-leader tree starts with just a central leader, but when it grows to about 7 feet, you stop its growth by bending it over, which slows growth, or cutting back to a weak side branch.
The tree you get from a nursery may be a single upright stem, or whip. Alternatively, you may get a "feathered" tree, an upright stem with some side branches. If your new tree is a whip, shorten it by a third to a half to promote branching. For a feathered tree, save well-placed branches and completely cut away all others. Always cut broken stems and dead or diseased wood back into healthy tissue.
For any of the three basic tree forms, begin branch selection the first season. Start with the first branch about 2 feet from the ground, then space higher ones about 6 to 8 inches apart. Strive for a spiral arrangement of branches so that each branch has room to spread. Also, choose branches that make wide angles (45°F to 60°F) with the central leader, because such branches are most firmly anchored to the stem.
For an open-center tree, once you have selected three or four branches, cut the central stem off just above the topmost branch. The tree then continues to grow upward and outward along the branches, now officially leaders (but not central leaders). As these leaders grow, make sure that none of their side branches originates so low that they interfere with each other.
If your tree is a central-leader or modified-central-leader type, induce the central leader to keep making new branches by cutting off about a third of the previous season's growth each year while the plant is dormant. If dormant-season pruning doesn't produce enough branching options, tip prune leaders during the growing season. Cut back the leader by a few inches each time it grows a few inches above the point where you want a side branch. The uppermost bud that remains after cutting back the leader usually grows to become an upright shoot, a continuation of the leader. Lower buds grow out to produce side branches. Select new side branches that are well spaced along the leader and firmly anchored to it.
The central leader on both central-leader and young modified-central-leader trees should remain as the dominant and most upright stem of the tree--the horticultural top dog. If the leading stem should grow into two equally vigorous stems, remove one of them immediately and completely. Also, don't let the central leader fruit in its first few years and don't let it bend over, because both circumstances would weaken its growth.
A Few Tips and Tricks
Suppose a sprout is emerging in a perfect position to become a side branch, except that it forms a narrow angle with a leader. Widen the angle by inserting a clothespin or toothpick as a wedge between the sprout and the leader so they form a 45- to 60-degree angle. If no side branch is growing where you want, cut a notch into the bark above a bud to make that bud produce a shoot. If a well-positioned side branch is trying to grow more vigorously than the leader, weigh it down just above the horizontal to slow its growth. What if the leader makes only feeble growth for the first season? Cut it back severely when it's dormant, or early in the season, to stimulate vigorous regrowth.
Mature Trees: Prune for Size and Regular Crops
Even after your tree starts bearing well in the garden, it will need annual pruning, but for different reasons than when it was young. Prune an established, mature tree to keep it from growing too large, to keep it healthy, and to keep it bearing regular crops of high-quality fruit.
Contain the growth of an overgrown tree by cutting back a few large branches either to where they begin growth or to weak side branches. Ideally, you should start pruning your tree to limit its size before it reaches full size. You can do this in two ways. Shorten the leader to a weak, horizontal side branch. Or, bend the leader over and weigh it down to weaken it. Use one of these techniques before it grows as high as you want your tree to grow.
Skillful pruning strikes a good balance between shoot growth and fruit production. How much pruning is needed to achieve this balance depends on how -- or, really, where -- the particular tree bears its flowers and hoig its fruits are. At one extreme are trees such as peach and nectarine. They bear fruit only on stems that grew the previous season, so they need fairly severe annual pruning to stimulate a flush of vigorous new shoots for the next year's crop. The traditional recommendation is to prune enough off a peach tree so that a bird can fly right through the branches. Apple trees, at the other extreme, produce fruit on long-lived, very short, knobby branches, called spurs, so they need little such stimulus. Many fruit trees lie between these two extremes.
Remove Some Potential Fruits
Pruning also balances crops by removing potential fruits. Especially with trees that produce large fruits, such as apple and peach, individual fruits tend to be undersized and less sweet if the crop is too heavy. Also, a heavy crop one year can result in a light crop the following year. By removing some stems that would have borne fruit, pruning prevents crop production only in alternating years and maximizes production of better fruits in terms of size and sweetness, particularly for large fruits. (Picking off some small fruits early in the season, just as they form, also improves the remaining and future garden crops.)
Shorten and Remove Some Stems
Each year, shorten some stems and remove others completely. Shorten stems where you want increased branching. Remove stems completely where you do not want regrowth, such as where stems are overcrowded. Complete removal is also the way to deal with watersprouts. These vigorous, upright stems shade lower stems and are not very fruitful, so cut them right to their bases as soon as you notice them.
Use a combination of pruning cuts to shorten some stems and eliminate others as appropriate. Even those small, fruiting spurs on apple and pear trees eventually need pruning for rejuvenation and to eliminate overcrowding. The kind of tree dictates the overall amount of pruning needed. The younger the stems on which fruits are borne, the more severe the annual pruning required.
Lee Reich lives in New Paltz, New York.
Photography by National Gardening Asscoiation, illustrations by Elayne Sears