The benefit of pruning forest-trees is more lightly thought of than it deserves. Upon this operation depends the healthy thrift of all members of the growth acted on, as well as its future deportment and usefulness.
To prune a tree so as to serve the purpose for which it is wanted, observation of its natural habit will soon teach the planter how much Or how little is required to be cut away. Care, however, is necessary that it be not pruned to such an extent as to weaken or check its growth, nor should the whole of the branches prunable be cut off at once, as some, which it is ultimately requisite to trim away, may at that particular stage of growth be beneficial to the tree of which they are members.
Again, it may be observed that there are many cases of failure from not pruning enough; so between these two questions the considerations of the planter must take a moderate tendency, in conformity, of course, with his own observations, in connection with the natural habit of the tree he is to practise on, and the purpose for which his exertions are designed.
The great object of pruning is to obtain a straight stem, regular outline of tree, and equalize the members necessary to support its thrift. For the first of these requirements it is usual to begin training while the tree is young, and for this reason the nursery is the place best suited to start from, as the limbs of the trees in their infancy are smaller and their tendency more easily observable then than if left tiU of greater maturity; besides, the wounds formed by the separation of young branches from their parent stem will not be so large as to require any serious attention.
The shade necessary for the protection of the tree-stem from the drying influences of the sun makes it necessary that the lower branches of young trees, especially if growing in open ground, be preserved for the purpose to which they are best suited; generally trees so situated require at least two thirds of their height as a source of shade to their stems, and for the production of that vital property naturally possessed by the leaves so indispensable to growth. But when trees are grown collectively, and for the production of timber, so that individually they shade each other, then they can be conveniently pruned to two thirds of their height, allowing only the remaining one third as a requisite shade.
The most suitable time for the pruning of trees is in midsummer, when the leaves are in full bloom and the sap in a state of quietude. They may also be pruned at the commencement of winter, as at this season any wounds formed will readily heal, owing to the influences of climate brought to bear upon the exposed parts. Some species, however, owing to the sparseness of sap-circulation in their systems, may be pruned at any time without injury; but the great desideratum in all instances is to effect the operation without having any cause to fear the result.
In pruning large trees, when the wounds are of considerable size, it is requisite that they be protected from the decomposing influence of moisture by applying a thin coat of common grafting-wax to the exposed wood; or varnishing the parts with a preparation of gum-shellac dissolved in alcohol will fill and dry the pores of the wound and exclude any injurious agencies.
The pruning of evergreens is not so generally necessary as for deciduous trees, the object to be obtained in the cultivation of them being so different that only the matter of taste will serve as a guide. Their principal uses being ornament and shelter, these requirements necessitate but little work for the knife, as for such purposes the trees are more beneficial and attractive when allowed to retain their natural fantastic diversity.