A good gardener will not allow a flowering plant to grow haphazardly. He will pinch off a wayward shoot or an excess bud. He is pruning.
So a tree, which is a large plant, should be pruned. Pruning is a natural and necessary process. It removes parts injured in the past and a building for the future.
There are more buds and branches on a shade tree that can develop. Many of these are suppressed by sunlight. Others become sick because of malnutrition or attack by insects and fungi. In the forest, trees prune themselves.
But nature takes her time doing it and is often violently ruthless. Over the years, the weakest limbs decay and drop. Sometimes, during a wind or ice storm, the whole arms of a tree are torn out, leaving ugly scars.
When he knows what it is all about, man can do a better job of pruning. Three questions are usually asked in any discussion of pruning: when to prune, what to prune, and how to prune.
Good Practice On Pruning
Pruning when the saw is sharp has always been good practice. Winter months are ideal times to prune because the leaves have fallen, and the pruner can better see what he is doing. Then, too, lawns are not disfigured, and there is less damage to plantings beneath a tree.
There are exceptions, of course. Trees that bleed in winter, notably the sugar maple, the birches, black walnut, and flowering dogwood, should not be extensively pruned during the dormant period.
There should be a reason for every cut. Generally, pruning falls into two broad categories:
- Structural pruning to remove weak and dead branches
- Corrective pruning to correct growing faults, eliminate interfering and interlacing branches and promote symmetry
Most everyone recognizes that leadwood and dying branches should be cut away in the interests of appearance and safety. But, equally important, it is done for tree sanitation.
Timely Pruning And Burning Of Bark
Timely pruning and burning the bark of all weak, dead, and dying elm wood is an effective method of checking the spread of Dutch elm disease. Burning the hark destroys the bark beetles, which overwinter as grubs. Otherwise, the beetles will spread the infection to healthy trees next Spring.
The two-lined chestnut borer, now an archfoe of oaks; the bronze birch borer; the hickory bark beetle; the linden borer; and the fruit bark beetle of the apple, peach, plum, and pear, can all become extremely abundant in sick and weak wood.
Pruning will help keep these pests under control. As a sanitary practice, it will also check such outbreaks as the sycamore blight, maple wilt, and anthracnose.
All too frequently, pruning stops with the removal of dead branches. It shouldn’t. There are many other reasons for pruning. Guidance is one of them. Guidance pruning is essential to young and middle-aged trees.
The object is to produce a strong tree by avoiding Y-crotches and the development of limbs so near each other that later growth will result in interference either at the base or farther out.
Take a long look at your shade trees now. Most people assume that trees should be allowed to grow at will. Notice wayward branches, limbs that rub one another, and weak Y-crotches.
Favorite Street Tree Norway Maple
The Norway maple, a common lawn tree, and the linden, a favorite street tree in some communities, have a habit of developing many slender branches, some of which rub one another. An excessively branched tree of this type can be helped by judicious thinning.
But it should be done over a two or three-year period. Removing too much wood at once will open up the tree to sunscald injury. And sunscald damage is followed by an invasion of bark beetles and borers.
Remember how thick the top of the shade tree on the front lawn was last Summer? It shaded the house so much that it made the living room dark.
When heavy winds blew, it was like striking a brick wall. You were afraid the tree would be blown over if a hurricane came.
Winter Pruning
Winter pruning will thin it. The top can be opened to permit air circulation and light entrance. The tree will benefit; so will the once-darkened house.
Taller trees can be lowered by pruning. Trees whose branches scrape your hat when you walk beneath may be made “taller.” Simply “raise” their lower limbs by removing them.
There are a few trees that cannot be improved by judicious pruning. Judicious is the word.
There is a vast difference between a person who knows what and how to prune and one who becomes a “butcher.”
Character Pruning
It should always be remembered that the natural form of most trees is more beautiful than an artificial shape.
Character pruning has as its primary aim the pruning of a tree so that its true branching habits will stand out as a beautiful silhouette against the sky. Uninteresting branches are lopped off.
The broad dome of the white oak should never be made to assume the weeping fan-top shape of the American elm.
The hard maple has a broad top and should be kept that way. How incongruous it would be to permit the pyramidal shape of a Colorado blue spruce to develop into an oval crown!
In its earlier years, the slender towering form of a pin oak can be kept that way in old age by the judicious use of a saw and pruning hook.
Three Principles of Pruning
Before beginning to prune, keep these three principles in mind:
1. Pruning the top of a tree invigorates the branches that remain.
e. Pruning the roots – done principally when transplanting a tree – lessens the food supply and retards top growth.
3. Removal of superfluous buds throws greater vigor into those that remain. Pruning away terminal buds induces the thickening of the branch system.
Tree Top Pruning
Always begin pruning at the top of a tree, then work down. It is easier to shape a tree by this method. Time is also saved in clearing the tree of pruned limbs.
There is a right and wrong way to see off a limb. The wrong way is to leave a stub, which may rot and break off to form an ugly knot hole or become an invasion point for fungi and insects.
Always cut a branch dose to the trunk swelling from which it originates. Keep the size of the cut to the practical minimum.
When removing large, heavy branches, make three cuts to avoid stripping the bark of the trunk.
The first should be an undercut halfway through a limb about 6″ inches from the trunk. The second cut is made on the upper side, several inches farther out on the limb or several inches closer to the trunk.
This will permit the branch to fall without stripping the bark of the trunk. Now, the third cut is to flush with the trunk to remove the stub.
Generally, the inexperienced worker errs by leaving too much rather than too little shoulder on the final saw cut. In removing dead branch stubs, the wound will heal more quickly if the pruner cuts somewhat into the collar of the callus instead of merely sawing off the dead stub.
Sometimes it is impossible to cut as far as the trunk or a larger branch. Then the cut should be made out of a smaller branch or vigorous bud.
Slant Cuttings
Slanting cuts should be made when removing parts that grow upright. This expedites callus formation and has less tendency to form a water-collecting pocket.
Small and inaccessible limbs can be removed with pole saws.
Small branches and twigs are generally removed with hand pruners or pole primers.
If the pruners bruise the hark on one side of the cut, exercise care to make certain the bruise is on the part removed. An upward cut with a sharp knife will give the best results on very small wood within reach.
All cuts an inch or more in diameter should be painted with a wound dressing, such as a mixture of commercial Bordeaux powder and raw linseed oil. This fills the exposed wood’s pores, checks sap’s evaporation, and prevents the entrance of fungus spores. So long as the wood is kept intact, there is no danger of injury resulting from pruning.
The best results are obtained when the tools are sharp. And if a tree being pruned is known to be diseased, sterilize the tools before using them again on a healthy tree.
When you have finished, stand off and ask whether the tree looks like no limbs have been removed.
The proof of good pruning is the complete absence of any conspicuous evidence of the pruning work. If the finished work measures up to that, you have mastered the art of pruning.
44659 by Dr. F. A. Bartlett