This section is from the book "The Gardener's Monthly And Horticulturist V24", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
It is doubtful whether there is any other subject connected with fruit raising upon which there is such a wide difference of opinion as that of pruning.
Two wide extremes are held by different men ; some holding that pruning should be done at almost all times and with but little limit to the quantity. On the other hand, there are those who are opposed to pruning at any time and in any quantity.
The one argues that nature knows the needs of her own productions better than man, and if it were best for the growing tree for a considerable portion of its annual growth to be cut away, it would either not be produced, or it would fall away of its own accord. And this is what does take place in the case of forest trees; when the growth is too thick so that some of the branches do not receive a sufficient amount of light and air, such branches die and fall off. By this process of natural pruning the lower branches of the trees in the thick forest have been gradually removed till the trunks are entirely devoid of them for many feet. From this it is argued that if fruit trees be left to this natural process of pruning, they will be both more healthy and more fruitful. But would this follow as a consequence of this let-alone system ? It appears to me there are very strong reasons for believing that it would not. It should be remembered that the conditions of the forest tree are wholly natural, while those of a fruit tree in the orchard are largely artificial. The forest trees are generally crowded so closely together that the sunlight and air are largely excluded from the lower branches, which being thus deprived of their natural stimulus, die and fall away.
The fruit tree, on the other hand, is, or should be, planted out in an open space where it receives abundance of both light and air, so that so far from its being deprived of its surplus branches by natural pruning, the tendency is to grow thicker almost without limit. Again, the acerb and astringent fruits that are produced by the trees of nature's own planting and pruning, are hardly to be compared with the highly developed, luscious fruits of our cultivated orchards. It is doubtful whether even those who contend for leaving the pruning to nature would be satisfied with that which is produced without the aid of artificial means. It has been my observation that orchards, even though composed of the better varieties of cultivated fruits, if permitted to go without any pruning, soon become so overgrown with useless, or, at least, surplus wood that the fruit, though abundant as to numbers, is very inferior as to quality. An excessive growth of wood is incompatible with the production of abundance of good-sized, high-flavored fruit.
For the development of fine flavor in fruit, it is essential that it be exposed to the rays of the sun while ripening. Fruit that is grown in the shade is always insipid compared with the same variety that has been freely exposed to air and sunlight. Some trees, if not kept somewhat in check by pruning, will run to wood to such a degree that but little of their vitality is left to produce fruit. Others with such an abundance of branches set such a large amount of fruit that none of it can reach much excellence. It is evident that a judicious amount of pruning will remove these evils by thinning out the surplus branches, thus concentrating the sap in a smaller number of branches and buds, causing a more vigorous development of the fruit. At the same time, this thinning out of branches admits the air and sunlight to all parts of the tree, causing a more perfect elaboration of the sap in the leaves, and of the juices of the fruit.
Assuming, then, that a certain amount of pruning is required for the fullest degree of excellence in the growth of fruit, I proceed to a brief description of the principles of pruning. And in this inquiry there are three things that present themselves as claiming attention and elaboration. First, the time when pruning should be done; second, what should be cut away in the operation ; and, third, how pruning should be done. As to the first, much depends on the object sought by the operation.
There are various and apparently contradictory ends to be attained by pruning. We prune to reduce the vigor of trees; to increase the vigor of trees ; to thicken the head of branches; to induce fruitfulness; to reduce the tendency to form fruit buds; to cause a more spreading growth; to induce a more upright growth, and various other purposes. From this it will appear that in order that pruning may accomplish the end desired, it is essential that it be performed under such conditions as will secure that particular object. It is evident that if it be not done with a correct understanding of the principles involved, a very different result may be produced than the one intended. The difference in result depends very much on the season of the year and condition of the tree when the pruning is done. In order to understand the physiology of pruning it is necessary to have some knowledge of the principles of vegetable physiology. The fruit tree is a living being influenced by soil, climate, and especially the seasons of the year. The internal condition of a tree does not differ so materially as the outward manifestations at the different seasons of the year.
No sooner has the leaf fallen in the autumn than the tree begins the process of accumulating a store of moisture charged with vegetable food for the use of the tree during the following growing season. This is evident from the fact, that if a tree be examined just after the fall of the leaf it will be found comparatively destitute of sap; but if the examination be made in the spring, the wood will be found full to repletion with the moisture that has been gradually accumulated during the winter. During this gradual increase of sap, there is a considerable amount of tree food carried up and deposited in various parts of the tree, near where it will be needed for the early growth of the season.
Of course the more branches and buds the tree has the more this plant food is divided, and the less relative effect is produced on each part. Now it is evident that if a portion of the branches be cut away early in the season, the remaining buds will receive a greater proportional amount of the nutriment accumulated afterwards. The result would be increased vigor in the growth of the remaining portions. If the desire is to increase the vigor of a tree, according to this theory, the pruning should be done as soon after the fall of the leaves as practicable. But if there is already sufficient vigor, pruning at this season will have a tendency to increase the number of branches, as the material laid up will cause adventitious buds to form which will produce numerous water sprouts that cause a thickening of the sprays that will increase the evil that was sought to be remedied by pruning. This explains why many persons complain that pruning only makes the matter worse.
If the desire is to reduce the vigor of a tree and thus cause it to form fruit buds and bear fruit, the pruning must be done at a time when the tree has expended the material for its season's growth; say about July or August. But a tree to endure much pruning at that season should be in great vigor, as severe pruning at that time strikes at the life of the tree. Between these two extremes there is a season during which the vigor of the tree will be but little if at all affected. This is evidently the best time to prune for the purpose of simply removing surplus branches. My experience and observation have led me to believe that the best time to prune, if this be the purpose, is just at the time the tree is making its most vigorous growth of the season. This, in the Northern States, is during the latter part of May and fore part of June, varying with the latitude and the earliness of the season.
What to prune will be determined in part by the purpose for which the operation is performed. But it is evident that all branches that cross and chafe must be removed. With most trees the pruning should begin at the center and progress outward. The head of the tree should be kept open so that air and sunlight may have free access. If a tree is inclined to grow lop-sided the branches are to be pruned off and cut back till a proper balance is secured. All water sprouts and other branches that start where they are not needed should be removed at once. The better way is to rub or pinch them off with the fingers as soon as they have started.
If a tree is too upright in growth, it may be made more spreading by cutting the branches back uniformly to buds that point outward. If on the other hand, the growth is too spreading, the pruning is to be done to buds pointing upward or inward. But little remains to be said on how pruning is to be done. The common fault of leaving a stub where a branch has been removed is to be avoided. The branch should be cut off with a smooth cut just where the swelling at the base begins, so that the wound will be just the size of the large part of the branches. Large branches are to be removed with a fine saw, and the wound pared perfectly smooth with a sharp knife, and then covered with a coat of white lead or shellac dissolved in alcohol.
Pruning done with intelligence and skill is a blessing; but if done in ignorance and in a bungling manner it were better not done at all.