The following information on fruit tree pruning comes from Five Acres and Independence by M. G. Kains. Five Acres and Independence is also available to purchase in print.
It is often said that nature makes no mistakes, perhaps so—from her standpoint! But she is apparently just as much interested in producing a sour, hard, inedible, little crabapple as a luscious Mackintosh or a Fall Pippin! Perhaps she is also as well pleased with her methods of developing trees that will break down because of weak construction or the entrance of decay as if she built them on sound engineering principles and protected them from internal rot. If our human opinions differ from hers it may be because of our selfish bias! But if, as we are told, we are “lords of creation” why should we not “lord it” over her as much in the construction and care of trees as in the selection of varieties that please our palates?
In Nature, plants grow thickly; each crowds the others, so that superfluous individuals and branches are destroyed. Under cultivation the distances at which plants are set and the relatively greater abundance of available plant food often increase both number and growth of branches, so unless pruned many more would continue to live than would be “pruned off” by Nature’s crude methods. Hence the necessity of our using improved methods of pruning to remove this superfluous wood, or, better, to prevent its formation and to favor the better placed limbs.
Methods of preventing damage are so simple and effective that anybody may apply them and as most of them cost nothing but a little time there is no reason why they should be neglected. They all depend upon a working knowledge of the underlying principles of plant life and growth. By understanding these even the veriest tyro may discover or identify trouble in its incipiency and literally “nip it in the bud”—often years before it would become actually threatening to the well-being of the trees.
Prevention of damage should begin with the receipt of the trees from the nursery or with the seedlings that start to grow where Nature has sown the seeds. Before planting the former, every root as thick as a lead pencil and every scraped, broken, mangled or otherwise injured root should be shortened back to sound wood. Best cuts are made with a sharp pruning knife, though a hand shear is useful, provided both its blade and its holding jaws are keenly sharpened so as to make clean cuts—not chewed or crushed wounds. Quick healing follows smooth cuts.
When the tree is planted it is imperative to remove at least 50% of the top, of all except unbranched yearling trees. (Chapter 33 and later pages of this one.) These “whips” or “switches” should never be cut because they are the “leaders” or main trunks of the trees. Among commercial orchardists 75% of two-year and older nursery trees is pruned off immediately after planting. Though to the novice this treatment may seem “heroic” it is based upon the sound principle that a balance between top and root must be reestablished or the tree will surely suffer, if not die. In any case where this pruning is not done the tree will be slow to recover.
The way to reestablish this necessary balance is to reduce the amount of branch area. Professional tree planters and especially commercial fruit growers who follow this practice rarely lose as much as one tree in a hundred planted.
When making this reduction of top it is highly advisable to govern the cutting by the positions and sizes of the various branches. First, note which are the sturdiest, next the distances between these on the trunk. When they are 12″ or more apart a stronger tree may be developed than where they are closer together and far stronger than when they are in opposite pairs or in bunches. Also a far better balanced tree may be developed if these three, four, or five strong, well separated branches point in as many different directions; so that, if viewed from above they would look like the spokes of a wheel with the trunk as the center. Never cut these until the last.
The first branches to cut off entirely should be the puniest and the poorest placed. The only puny branches that should ever be saved are such as are well placed and point in the desired directions, even though a thriftier branch near by but badly placed must be sacrificed. The puny branch will probably develop well when the competition with the other branches is reduced by pruning.
If at any time two branches are placed so close together and on the same side of the trunk that they would interfere with each other the one more poorly placed (usually the lower one) should be cut off completely, though sometimes it would be advisable to let it remain when its position is farther up or down from the next desired branch above or below. After puny and interfering branches have been removed so that only the strongest remain these latter may be shortened from 30% to 60% so as to help reestablish the balance between top and root.
Whether or not the main stem or “leader” should be cut is a disputed question. For many years my conviction is that it should not be because, when this is done, new branches are almost certain to form in a cluster near the top and thus lay the foundation of one of the commonest and most distressing tragedies of tree growing—the breakdown of the top due to the splitting of the Y-crotch or crotches formed by the branches at this point (Chapter 33).
The lowest branch of apple, pear and sweet cherry trees should be 30″ to 36″ from the ground; those of peach, sour cherry and plum, 18″ to 21″ because low-headed trees are less likely to be injured by high winds, the fruit to be blown off and less difficult to reach at picking time, much of it being gathered direct from the ground or with only short ladders. Then, too, in jury from sun scald of the trunks is reduced, so is the difficulty and cost of harvesting and spraying.
During the first few years judicious pruning with the knife will save not only much time and labor with saw and loppers in later years but will build stronger, more symmetrical specimens than by any other treatment. Still better, nipping undesired buds and soft inch-long shoots will save even knife work. The same principles apply to each frame limb as to the development of the main trunk—spacing the side branches far apart and pointing in different directions, except that on the under sides of the frame limbs no branch should be allowed to develop because it would be too much shaded by the main branch. Better the watchful eye than the active saw! It will see prospective undesirable developments and prevent the necessity of using the saw in later years.
Actually, while the trees are young—up to the fourth or fifth year with apple, pear and sweet cherry and to the third or fourth with sour cherry, peach and plum—about the only pruning necessary after the trees have had their preliminary treatment just after planting should be the removal of occasional branches that would sooner or later interfere with the ones desired and the more or less shortening of rampant branches that threaten to rob the others of food, light and air. The less pruning done during this period the better, because the removal of wood during the dormant season tends toward the production of still more wood. Thus, severe pruning during winter may postpone fruit bearing, perhaps indefinitely, if persisted in annually.
Whenever a branch must be cut off make the wound as close as possible to the part that is to remain so there will be neither a stub nor even a shoulder. Closeness of the wound to the main flow of sap favors healing. When a stub is left decay is sure to follow.
As fruiting age approaches be sure you know where to expect fruit. On apple, pear, cherry, plum and apricot most of the fruit is borne on “spurs” as the short twigs are called. Never cut them off simply because you like to see well manicured trees. One of my clients did this with the result that even such precocious varieties as Yellow Transparent and Duchess of Oldenburg did not bear a fruit until they were 12 years old, whereas they usually start when a third that age or even less!
Intelligent pruning for fruit presupposes knowledge of the appearance and position of the fruit buds. Blossom buds are rounder and plumper than branch buds. Apples and pears bear most of their blossoms at the tips of spurs in clusters surrounded by leaves also contained in the same “cluster buds.” Occasionally flowers come on the sides of twigs produced the previous year. Because of the terminal position of the fruit on the spurs and because fruit production is an exhaustive process the direction of growth changes each year and fruit is borne on the spurs only each second year. With age the spurs become gnarled and crooked, but, if healthy may be as productive as younger spurs.
Cherries bear much of their fruit on spurs, but because the terminal bud is almost always a branch bud the spurs are relatively straight. Most of the other buds on the spur produce blossoms, though an occasional one may develop a branch spur. Blossom buds are also borne near the bases of annual growths of the previous year.
The plum and the apricot bear their blossom buds partly on spurs and partly on young growths, but in more varying proportions than with the cherry.
The peach is different. It produces some blossoms on wiry twigs on the larger branches, but these growths live for only a few years. By far the largest part of the blossoms are borne, one on each side of the pointed branch buds on growths of the previous season. They can be easily recognized, first because of their position and second because of their roundness. Sometimes the bud between the pairs just mentioned is a blossom bud.
Never prune off or break the spurs of any fruit tree unless there are too many or unless failing, because a spur removed is gone forever. On the other hand, always cut back peach shoots severely—often 50% to 75%. Unless you do the tree will extend farther and farther out each year and become more and more likely to break because of the increased leverage. Again, such annual pruning will concentrate the fruit bearing area in the reduced space and thus also reduce the amount of fruit thinning that must be done in midsummer.
The quince is again different. It bears its blossoms at the ends of new growth that spring from buds that have wintered over. Pruning for fruit, therefore, consists in keeping the tops of the bushes fairly open and reducing both the number of annual growths and shortening the remaining ones a third to a half.
Though many trees die prematurely from disease, neglect of insect attack, probably the commonest cause is breakdown. At first glance this may seem to be because of overweight of fruit, ice or snow or stress of wind, but examination will show that though the trunks may reveal interior decay the original cause is bad heading—the development of frame or main branches so close together they either pull against or shade each other until they break down or must be removed. In the former case the tree is ruined at once; in the latter decay is often admitted to the heartwood which is steadily eaten away until the interior is perhaps hollow. Hence the importance of training young trees so as both to avoid such disasters and to develop branches free from fault as to position with respect to the trunk and to each other.
The home orchards of my boyhood were developed according to the principle formulated by Downing; namely, “Every fruit tree grown in the open orchard or garden as a common standard, should be allowed to take its natural form, the whole efforts of the pruner going no further than to take out all weak and crowded branches.” Many of the trees so developed by my grandfather and great-uncles between 1850 and 1875 are still bearing, even though since the passing of these men, they have not been as well tended by later owners.
In contrast with such records tens of thousands of trees trained on the “vase-form” or “open center” plan, or because nurserymen cut the “leaders” have broken down at a quarter the age of these veterans. In such cases the branches having developed in clusters pull against each other and break down or when allowed to develop to bearing age before removal usually leave wounds through which decay enters the heartwood as already noted and thus precedes, in fact, assures, breakdown.
Removal of large limbs is always a menace to the well-being of trees. The only limbs larger than 1″ in diameter that should be removed are dead ones, those so badly diseased that they cannot be saved, or those broken by accident. Even the removal of 1″ branches may be avoided by proper training while the trees are younger than five years, and most of them during the first three years!
Because of the heavy losses of trees and differences of opinion as to what are sound principles of tree training various experiment stations have conducted investigations to determine correct ways to train young trees and have reported findings in bulletins. One such undertaken by the Illinois station is reported in a 125-page bulletin (No. 376) from which the following conclusions have been chosen and condensed. The italics are mine.
Growers attribute death to various causes, but do not realize the part that pruning plays directly or indirectly. Wounds are an important factor in death and the initiation of the unprofitable period. They are often attributable to the way in which the tree was headed. Poor heads in trees now mature are due to the severe heading-back cut given when the young tree was a whip. Efforts should be made to produce frameworks in which equilibrium will be maintained as nearly as possible, especially late in the tree’s life when wounds are likely to do most damage.
In forming the framework, very narrow angles and the excessive development of one main branch are to be avoided as these factors lead to splitting of the head. Vertical spacing of branches is desirable to avoid “smothering” of the leader. Problems of training are greatly simplified by starting the framework branches by disbudding to groups of buds, thus avoiding the dominance and the sharp forks that result from severe heading back. Uniformity is also secured among the main branches which are subordinate to the central leader. To train trees by disbudding the following steps are recommended by W. A. Ruth and V. A. Kelley, authors of the bulletin.
Of the three new methods of heading reported in the bulletin disbudding to groups of buds is considered the best and is therefore recommended in preference to the others. (Fig. 40.) The steps are based not only upon the data recorded, but also upon incidental observations made as the study progressed.
First season. Use vigorous one-year whips which have not been allowed to dry out before planting. [Fall buying and heeling-in may be necessary to assure plumpness as storage too often shrivels the trees. M.G.K.] Incline them slightly toward the prevailing wind. If they are tilted so far that the lower side becomes an underside, shoot development will be discouraged in that direction but will start to grow through the tree.
Just before growth starts disbud the whips with a sharp knife to groups of three or four consecutive buds, each group at the height where a frame-branch is wanted. Intervals between groups should be about 8″ from center to center. [I prefer 12″ or more because greater strength is thus assured. M.G.K.]
The whip should not be cut back. Let the tree grow undisturbed throughout the entire season.
Second season. At the beginning of the second growing season choose one branch at each height for the permanent framework. Select for uniformity of diameter and length (to secure balance), for proper direction (location in a spiral), and for an angle suitable to the variety [A wide angle makes a stronger limb connection with the trunk than a narrow one, which is likely to break down. M.G.K.]. The laterals left on drooping varieties like Jonathan and Winesap, should have a more upright direction than on upright varieties like Yellow Transparent and Delicious. In any case the angles should not be so close that bark will later be caught in the crotches. Proper angles will usually fall between 20º and 45º from the vertical.
Remove or head back lightly all vigorous laterals not to be left for the permanent framework. Their removal is sometimes the better treatment because it establishes the permanent framework branches at once and avoids the necessity of securing dominance gradually. It also avoids the difficulties which result from heading back. However, pruning vigorous trees heavily at this time induces such succulent growth in the laterals left for the permanent framework that they may be bent out of shape by wind and in the most upright varieties the angles between some of the framework branches and the trunk may become too acute.
Short horizontal laterals which will not compete with those selected for the framework, should be left to increase the diameter of the trunk as much as possible. It is not necessary or desirable to head back the laterals to be left permanently. If they are left alone, they will become branches coordinate with the central leader, an important step in the easy development of the modified central-leader tree.
Third season. At the beginning of the third growing season replace any poor laterals with better ones which may have developed from buds that remained dormant or from shoots that grew poorly during the first season. This may be necessary on poorly grown trees, on trees that have been mistreated before planting, or on trees that have been poorly planted. If necessary, higher laterals may be selected for the permanent framework at this time.
Remove any vigorous misplaced shoots. Let all other growth remain. It is seldom necessary to head back for balance, but occasional laterals may be removed for this purpose.
Laterals in the upper part of the tree should be thinned out if the tree tends to become top heavy. The central leader, however, should not be removed or headed back because it is to be used as the highest branch in the main framework. It is to be kept equal in size with those lower down, preferably by removing laterals.
Fourth and Following Seasons. Prune as little as possible. By this time the three to five main framework branches should have established themselves, and only an occasional vigorous new shoot should need removal. It may be necessary to remove a few branches to keep the tree balanced. Since the central leader is to be the highest main framework branch, coordinate in size with those lower down, its vigor should be reduced, if it tends to outgrow the lower branches, by removing some of its laterals.