This section is from the book "The Gardener's Monthly And Horticulturist V22", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
Read before the Nurserymen's Convention, at Chicago, June 17, 1880.
Trees suffer more from the effects of the sun, directly and indirectly, than the majority of tree-planters will acknowledge or comprehend. Very often the unhealthy condition of trees is attributed to various causes, such as "poor stock" - fault of the nurseryman - soil, insects, etc.; whereas the first cause of trouble is improper exposure to the sun. Young trees are trimmed up by cutting off all the side branches by the nurseryman in order to give the tree a good appearance, which is very well as long as the tree remains in the nursery, for there it is protected by its neighbors; but when set out in orchard rows, the long smooth stem will suffer more or less by the exposure to the sudden changes of temperature caused by the sun, and unless well staked are very apt to lean over from the winds, in which condition the sun's rays strike the tree more directly, causing the bark on the exposed side to decay, and making it attractive to insects. Apple trees in this condition are very sure to be attacked by the flat-headed borer (Chrysobothris femorata, Lee.) The insects and sun together soon ruin a tree.
In reference to Apple trees especially, I think they would be healthier and longer lived if we would copy after nature more than we do. For example, if we allow an Apple tree to grow up from seed, never turning or crowding it, we will have nothing more than a large bush; but, you may depend upon it, there will be no sun-burn on that tree, there will be no flat headed borers, no sap-sprouts, it will not lean at an angle of 45° from the wind; and if on average good soil, will be a perfectly healthy and long-lived tree.
Now I do not propose that we should grow our trees in this way, but I do think that we might come a little nearer having perfect and healthy trees by elevating the art of tree pruning and by. copying to a greater extent from nature. Dr. John A. Warder says, in one of his works, speaking of nature's pruning: "She prunes and trains magnificently, and gives us models for imitation".
As far as I have observed, in nature the healthiest trees are those on which the side branches have been allowed to grow. When a grove of trees grow up by an undisturbed effort of nature, they will effectually protect themselves against the sun and winds; those on the exposed sides remain shorter and retain their side branches, so that the branches of the tallest reach down to the next shorter, and these in turn to the next, and so on down to the shrubs, and these to the grass. Why is this so if it is not for the protection from the sun and winds. If the short trees and shrubs are cut away the rest will soon decay, not on account of the wind alone, as we are usually told, but by the sun also; for I claim that the exposure to the sun has as much to do with it as the winds.
Where trees must be trimmed up high, I would allow the side branches to grow (although they might be kept short) until the top was large enough to shade the trunk, not from the summer sun only, but from the winter sun as well, which is probably the most injurious.