This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
We write line upon line relative to the subject of transplanting, because at this season it is a labor of almost daily occurrence with every horticulturist, and we feel that he can not too well consider the importance of certain principles in its practice. All removals of trees or plants, except those grown in pots, must of a necessity involve a certain amount of injury and reduction to the roots; and as roots are the important medium to support life and growth, their reduction at a season when the tree is nearly in a dormant condition causes less injury than when there is vigor of growth and demand for life-supplies by swelling buds or foliage. We know some advise-late spring planting, and if the spring is backward, or great care be taken alter planting, the work may be succeasful; but, as a rule, the practice should not be commended. The moment that buds begin to push, that instant the roots resume active functions, and any injury by breaking, etc., is more sensibly experienced than when the same injury has been created during the perfect dormant condition of the plant, and a reasonable time been given it to callus or heal over before being called on for labor in supplying buds and foliage with food for digestion.
Our advice to all who must plant in the spring is to perform the work as early as possible.