Traditional rules for pruning date back scores of years. One example is the rule that pruning of trees should always be done in late winter…usually February. This rule is hundreds of years old, but we know that it can be broken.
Where did this rule come from anyway? We think that it originated centuries ago when gardeners on estates were obliged to be doing some sort of useful work (to earn their keep, even in winter). With little other field work possible, the practice became a ‘rule’ that tree pruning should be done at this time.
As a result, living with the heritage of this rule, many persons today are reluctant to do any pruning in summer months. But, the old rule applies mainly to deciduous shade trees and some shrubs. Certainly, the Illinois Extension guide (http://urbanext.illinois.edu/fruit/tree.cfm?section=tree) says that fruit trees are best pruned in early spring. However, that doesn’t apply to every situation. Many trees, such as crabapples and most fruit trees, and yes, even shade trees, can successfully be pruned lightly in June and July.
This month of June is a time for pruning flowering shrubs and fruit trees. Spring-flowering shrubs (those that bloom before June) such as lilac, spirea, weigela and others are petering out by now. Magnolia and forsythia are long past. If you want them to flower again next spring, but you also want to cut back any excess growth, then now is the time to do so, not later.
Why? Because all during the rest of the summer these shrubs are forming their flower buds for next year’s bloom. So, DO NOT prune them over the winter or early next spring because you would be cutting off all their flower buds. Always prune right after they have finished flowering.
My forsythia here is a great example. It blooms on “old wood,” that is, buds formed the previous year in late summer. If it had been pruned back in February, there would have been few flowers here in April.
Now is the time to prune fruit trees for a different reason. Pruning (thinning) excess fruit at this time ensures a greater yield this year, and helps the tree to bear well each year. Apple, pear, peach and apricot trees should be pruned in the first two weeks of June; plums anytime in the last two weeks.
The purpose of thinning is to provide each developing fruit with an optimum supply of sugar for its growth. To achieve this optimum ratio of leaves to fruit, we thin branches by controlling the spacing between fruits. For apples, peaches, pears and nectarines, only one fruit is allowed to grow every 6 – 8 inches along a branch. Plums and apricots are thinned 2 – 3 inches apart.
On apple trees, most of the fruit grows on little short side shoots called spur shoots. The spur shoot usually has several young fruit surrounded by a cluster of leaves. When thinning fruit from a spur shoot, remove all but one fruit and be careful not to break or injure the spur because it can bear fruit for about 10 years.
However, there is a biological reason not to prune anything beyond mid July. Pruning in late summer can stimulate new growth. In this case, the new stems and buds may not have enough time to become winter-hardy before the first hard freeze
Thinning not only improves the quality of the crop, it also benefits the tree. A thinned fruit tree will have enough excess sugar to enable it to go through the normal processes that ready it for winter survival.
Depletion of stored sugar because of a heavy crop can also cause the tree to bear hardly any fruit, or none at all the following year. The tree will need another summer of building up sugar reserves before it can set and bear fruit again. This phenomenon is called alternate bearing, and once a tree gets into this kind of cycle, it may not recover to annual bearing for many years.
In early June, fruit trees normally drop several fruit as a matter of course. Wait until after this “June drop”. Then, thin by handpicking the excess fruit as much as you can, leaving only one fruit according to the spacing as given above.
Copyright © 2010 – Margaret Balbach