The proper season for planting is not everywhere the same. Where spring is the best season - north of the thirty-seventh parallel generally - the right time is when the frost is out of the ground and before budding or growth begins.
Trees cannot be thrust into a rough soil at random and expected to flourish. They should be planted in well-worked soil, well enriched. If they cannot be set out immediately upon receipt, the first step is to prevent their roots from drying out in the air. This may be done by "heeling in" the trees - that is, burying the roots in fresh earth and packing it enough to exclude the air. Evergreens in particular, which are always transplanted with a base of earth about the roots, are very easily killed by allowing the roots to become dry. Before planting cut off the ends of all broken or mutilated roots; if it is a broadleaf tree, prune the tree to a few main branches and shorten these. Evergreen trees should not be pruned. Dig holes at least three feet in diameter and two feet deep. If the soil is poor, they should be four feet in diameter. Make the sides perpendicular and the bottom flat. Break up the soil in the bottom to the depth of the spade blade. Spread on the bottom 12 or 15 inches of good topsoil, free from sods or other undecomposed vegetable matter. On the top of this layer spread out the roots of the tree with none of them in a cramped position and cover them with two or three inches of fine topsoil. Firm the soil about the roots, water lightly, and after the water soaks in fill the hole with good earth, continuing to firm it, but leaving the surface loose and a little higher than the surface of the surrounding soil.
When planted the trees should stand about one inch deeper than they stood in the nursery. They should be planted far enough apart so that at maturity they will not be crowded. This is especially important, for the trees will not grow well unless they have an adequate supply of light and moisture.
Young trees should not only be properly transplanted but should be cared for until they become so well established that they will grow without danger of dying of neglect.