Chapter 4
PRUNING THE TREES
Pruning is not an entirely artificial operation as one might at first thought suppose. It is one of nature's most common processes. Nature accomplishes this result through the principle of competition, by starting many more trees on a given area than can possibly survive. In the same way there is a surplus of buds and branches on each individual tree. It is only by the crowding out and the perishing of many buds, branches, and trees that others are enabled to reach maturity and fulfill their purpose. This being too slow and too expensive a process for him, man accomplishes in a day with the knife and saw what nature is years in doing by crowding, shading, and competition. Proper pruning is really an improvement on nature's method.
Neither is it true, as some claim, that pruning is a devitalizing process. On the contrary it is often stimulating and may actually increase the vigor of a weak or declining tree. All practical experience teaches us that pruning is a reasonable, necessary, and advantageous process. True, it is often overdone, and improperly done. As in many other things, certain fundamental principles underlie and should govern practice. When these are known and observed, pruning becomes a more simple matter.
Heavy pruning during the dormant or winter season stimulates the growth and tends to increase the production of wood. In the same way pruning during the summer or growing season stimulates the growth and tends to induce fruitfulness, if the tree remains healthy. But this fruitfulness is apt to be at the expense of the vigor of the tree. On the other hand, the pruning of the roots of a tree tends to check the growth of wood, the same as poor feeding. As above noted heading back a tree when dormant tends to stimulate it to a more vigorous growth.
The habit of growth of a variety has much to do with its pruning. Some varieties of apples are upright, others are spreading growers. Climate and locality greatly affect these habits of growth. So also the habit of a young tree often differs from the habit of the same tree in old age. The tendency is for a tree to continue its growth from its uppermost or terminal buds. Although the heading in of new growth checks this upward tendency and throws the energy of the tree into the development of lateral and dormant buds, nevertheless the pruned tree soon resumes its natural upward growing habit.
Plant food is taken up by the minute tree rootlets in solution and carried to the leaves where it is elaborated and then returned for use to the growing tissues of the tree. Whenever there is any obstruction above a bud the tendency is to throw the energy of the branch into a lateral bud, but if the obstruction is below the bud the branch merely thickens and growth is checked. When too heavy pruning is practiced the balance between the roots and top is disturbed. This usually results in what are commonly known as "suckers." These are caused by an abnormal condition and while they may be the result of disease or injury to the tree, they are often of great value in restoring or readjusting the proper balance between the roots and top.
Pruning a tree is a way of thinning the fruit and a good one. It may sometimes be used to influence the bearing year of trees like the Baldwin, which have an alternate bearing habit, but this is a more theoretical than practical method. Fruit bearing is determined more by the habitual performance of the tree than by any method of pruning, and this is especially true of old trees. It is easier to influence young trees. Conditions which tend to produce heavy wood growth are unfavorable for the formation and development of fruit buds. A quiescent state is a better condition for this.
REASONS FOR PRUNING.--With these fundamental principles in mind we may safely outline a method of pruning an apple tree. As the desired end is different so will the method of pruning a young tree differ from that of an old one. There are five important things for which to prune a young tree, namely:
1. To preserve a proper balance between the top and root at the time of setting out. This usually means cutting off the broken and the very long roots to a reasonable length and cutting back from one-half to two-thirds of the growth of the previous season.
2. To make the top open in order to admit the sunlight freely. In the humid climate of the Northeastern States, it is usually advisable to prune a tree so as to have a rather open top. This is necessary in order properly to color and mature the fruit.
3. To regulate the number of limbs composing the top. Probably three branches well distributed on the trunk would make most nearly the ideal head, but as these cannot always be obtained the best practice is to leave from three to five branches from which to form the top.
4. To fix the branches at the proper height from the ground. This is more or less a matter of opinion, some growers preferring a low and others a high head. The character of the tree growth, the method of culture, and the purpose of the tree whether temporary or permanent greatly influence the height of the head. An upright growing variety should be headed lower than a spreading one. Trees kept in sod or under extensive methods can well be headed lower than those under more intensive culture where it is desirable to carry on cultural operations close around them. Permanent trees should be headed higher than temporary trees. Apple trees should seldom be headed lower than a foot from the ground, nor more than four feet above it. For upright growing varieties intended as permanents, the writer prefers three to three and one-half feet and for more spreading varieties four feet; while for temporary trees eighteen inches should be a good height.
5. To do away with weak crotches and to remove crossing or interfering branches. A crotch formed by two branches of equal size, especially when the split is deep, is a weak crotch and should be avoided. Strong crotches are formed by forcing the development of lateral buds and making almost a right angle branch from the parent one. All branches which rub each other, which tend to occupy the same space with another, or which generally seem out of place, are better removed as soon as any of these tendencies are found to exist.
IDEALS IN PRUNING.--The general method of pruning the old trees and the ideal in mind for it will also influence the pruning of the young tree, especially the shaping of it. Once determined upon, the ideal should be consistently followed out in the pruning of the tree as it becomes older. As the tree comes to bearing age it will be necessary to prune somewhat differently and for other purposes. These we can conveniently consider under six heads:
1. Every tree should be pruned with a definite ideal as to size, shape, and degree of openness in mind. To have such an ideal is very important. It is only by industriously and consistently carrying it out that the ideal tree in these respects can be ever obtained. Haphazard cutting and sawing without a definite purpose in mind are really worse than no pruning at all.
2. It almost goes without saying that to remove all dead, diseased, or injured wood is a prime purpose of pruning. Dead and injured branches open the way for rot and decay of contiguous branches, and disease spreads through the tree. The removal of all such branches is as essential to the health of the tree as it is to its good appearance. In removing them the cut should be made well behind the diseased or injured part to insure the checking of rot and disease.
3. All mature apple trees should be so pruned as to keep them in the most easily manageable shape and to facilitate in every possible way the operations of tillage, spraying, and harvesting. It is most important to have the tree low enough down so that spraying and picking can be easily done. It is difficult to spray properly a tree which is more than twenty-five feet in height. Even this height necessitates a tower on the spray rig and the use of an extension pole. An apple tree should be so pruned that all the fruit can be readily picked from ladders not longer than eighteen to twenty-two feet.
Of course, if the tree has been allowed to get higher than this under previous management, sometimes we have to make the best of a bad situation. If the trees are too high head them back by cutting off the leaders, but it is not always wise to lower all trees to twenty-two feet. Heading back of old trees will be more fully discussed in the chapter on "Renovating Old Orchards." Ladders longer than twenty-two feet are heavy and clumsy to handle.
If cultivation is to be carried on close up under the tree the lower limbs must be pruned so as to allow this. It is not necessary, however, to drive a team closer than twelve or fifteen feet from a mature tree, contrary to the common belief and practice. Cultivation is least important in the first few feet of space around a mature tree. By the use of set-over tools, all that is necessary can be well cultivated without crowding the team under or against the branches.
4. As has been pointed out in the discussion of the pruning of young trees, in humid regions where the sunlight is none too abundant through the growing season, the open head is most desirable. Sunlight on the leaves as well as on the fruit is essential to good color of the fruit, and good color is a very important factor in the flavor and attractive appearance of the fruit. An open center with upright growing leaders removed gives the greatest opportunity for sunlight to penetrate through the tree.
5. As we have seen, pruning in the dormant season tends to increase the vigor of the tree. Thus winter pruning serves to secure a normal and vigorous wood growth, which is most essential to a healthy fruit-bearing tree. On the other hand, such pruning may be excessive and produce wood growth at the expense of fruit buds, throwing the tree out of bearing.
6. The sixth and last reason for pruning is to regulate the number and distribution of the wood and the fruit bearing buds. The proper balance between these is greatly affected by pruning and can be best regulated by experience with the particular tree or variety. A perfect balance is hard to get, but with study and skill it can be closely approximated. Pruning, too, may thin the fruit, as removing branches removes fruit buds. This is best done by removing small branches near the ends of larger ones. It is a much cheaper method of thinning than picking off individual fruits, but not as effective.
TIME OF PRUNING.--The particular time of the year for pruning is not vital. As between summer and winter pruning, winter is to be preferred because of the physical effect on the tree. Summer pruning is an unnatural process and should only be practiced as a last resort to check growth or induce fruitfulness, as it may result in injury to the tree. It is essential that a tree mature its foliage, which it frequently does not do after summer pruning. Diseased, dead, or injured wood should be removed when first observed, summer or winter.
Spring is the logical and usually the most convenient time to prune on the general farm. While dormant season pruning may be done at any time between November 1st and June 1st, the cuts heal more rapidly in the spring when the sap begins to flow. In regions subject to severe and drying winds in the winter, pruning should be deferred at least to late winter. Considered from every standpoint, March and April are quite the best months in which to prune. After the removal of useless branches, the normal amount of food material is delivered to fewer buds under greater sap pressure and the remaining buds are made more strong and vigorous.
In removing small branches with a knife or other cutting tool, the cut should be made upward from below and opposite a bud. On upright growing varieties the last bud left should be an outside one to induce the tree to spread as much as possible, while on spreading trees leaving as the last bud an inside one has a tendency to make the tree grow more upright. Always cut close to the parent branch, never leaving a stub no matter how young or old the tree.
Cuts of lateral branches should be made just at the shoulder of the branch where it joins the parent. A cut behind the shoulder will not heal, neither will one too far ahead of it. A stub left on a trunk or large branch does not heal, but soon begins to rot at the end where the heartwood is exposed. This gradually works back into the main branch and the tree finally becomes "rotten at the heart." All that is needed to complete the destruction is a heavy wind, an ice or a snow storm, or a heavy load of fruit.
All wounds more than two inches in diameter should be painted either with a heavy lead paint, which is preferable, or with some gas tar preparation. These things do not in themselves heal a cut, but they keep out the decaying elements, air and moisture, thus helping to preserve the branch and by protecting it to promote healing in nature's way. A little lamp black will serve to deaden the color of the paint.
PRUNING TOOLS.--The best tool to use in pruning is one which brings you nearest to your work and over which you have the greatest control to make all kinds of cuts. In the writer's experience no tool does this so smoothly and conveniently as a properly shaped saw. A good saw should be quite rigid, rather heavy at the butt, where its depth should be about six inches, tapering down to about two inches at the point. It should have a full, firm grip, be not more than thirty inches long, and should always be kept sharp. Two-edged saws should not be used because of the injury done to the tree when sawing in crotches.
Cutting shears are often very useful, especially the smaller, one-handed type which is almost indispensable in pruning young trees. The larger, two-handled shears are useful in thinning out the ends of branches or in heading back new growth. They should not be too heavy, as they are tiresome to use. The extension handled types are too cumbersome, too slow to work with, and the operator is of necessity too far away from his work for the best results.
FRUIT THINNING.--A matter which is quite nearly related to pruning is thinning the fruit, and may properly be treated here. That this is not as common a practice with most fruit-growers as it should be, the great lack of uniformity in our ordinary market apples is ample evidence. Many persons will at once raise the question as to whether or not it is practicable to thin the fruit on large apple trees. The answer is that many growers find it not only practicable, but most profitable to do so. Wherever fruit of a uniform size and color is desired, thinning is a practical necessity, especially when the crop of fruit is heavy.
The proper time to thin the fruit is just after what is commonly known as the "June drop," i.e., the falling off of those fruits not well enough pollinated or set to hold on to maturity. In thinning the fruit should be taken off until they are not closer than from four to six inches apart on the same branch, although the distance apart on any branch will depend somewhat on the amount of the crop on other parts of the tree. Never leave clusters of fruit on any branches, as some of them are sure to be small and out of shape. Furthermore two apples lying together afford a fine place for worms to get from one apple to another and they seldom fail to improve the opportunity. Step ladders and ordinary rung ladders are used to get at the fruit for thinning. The cost of the operation is not nearly as large as might appear at first thought and in practically all cases is a paying investment.