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.
Pruning the roots of trees is an operation conducive to fruitfulness not practised to that extent which it merits. In the hands of intelligent cultivators it is a valuable expedient, much more certain in its effects than many of the so-called dwarfing systems by grafting. Indeed, many of the stocks used for this purpose grow so vigorously in this climate, as to defeat the object in view. The mahalab is used as a Btock for dwarfing cherries, in Europe; here, they grow as strong upon it as on the mazzard. Even the quince will not check the vigorous growth of some pears, and are, in consequence, many years in arriving at a bearing state. Pear culture on the quince, although beautiful in theory, does not seem to give entire satisfaction in general practice. Many are inclined to believe that they are short-lived when thus grafted. To such it may be useful to know, that all the advantages claimed for dwarf stocks can be derived from skilful root pruning.
Many expedients in the culture of trees that we are apt to consider only of recent application, have long been practised. Such operations to induce fruitfulness, as bending down the shoots, cutting the bark, or ringing the branches, root pruning, etc., were practised during the last century. Darwin, seventy years ago, alludes to these practices in the following comprehensive sentences: -
"If prouder branches, with exuberance rede, Point their green germs, their barren shoots protrude, Wound them, ye sylphs, with little knives, or bind A wiry ringlet round the swelling rind: Bisect, with chisel fine, the roots below, Or bead to earth the inhospitable bough".
The advantage of root pruning is, that you can plant a young tree in a favorable position for luxuriant growth, and, after it has attained a size to bear a crop, throw it into fruit at once. This is effected by checking the growth in time to admit of the formation of wood buds. By digging a trench round the tree a few feet from the stem, at the present time, and cutting through the strongest roots,.wood growth is checked, and fruit buds are formed before the trees become deciduous.. Spring has been recommended for the operation, but the period of growth is the proper time-to produce immediate effect. This treatment may be performed on all fruit-trees that nave attained a size for bearing a crop.
The root pruning of trees as a means of promoting fruitfulness does not seem to meet with much favor. As a system for general culture it will not, of course, be popular, neither is it necessary. Occasionally, however, it may be practised with decided advantage. Where fruit trees are growing in very rich soil, such as in small, highly cultivated gardens, and produce annually an immense crop of branches, but no fruit, cutting off a few of the strongest roots is at once the most simple and certain method of checking growth. If this is carefully performed early this month, fruiting buds may be formed before the completion of growth.
C. F. Tour perplexity in the differences of opinion which as you truly say exist about root-pruning, is not to be wondered at. The reason of this diversity of opinion is easily explained. Where it is practiced by persons who have a competent knowledge of the laws of vegetable physiology it is both beneficial and a safe operation as regards the permanent health of the trees; but when practised by others who have not that knowledge it is frequently quite the reverse. Without writing a dissertation on the subject we can only say, yon had better not practice it except in the case of a fruit tree which appears healthy, but which whilst making strong growth fails to give a crop of fruit. Generally speaking, in such a case it will be beneficial.
Root-pruning of fruit trees should be done early in the autumn, and not in the spring. Nor can we advise you as to whether such root-pruning would tend to the production of fruit-buds in your trees. It would be useless, unless the trees are over-lniuriant Taking up the trees in autumn, and planting them on mounds of lighter soil placed on the surface of your clayey ground, would be better treatment, probably; but we have not sufficient information from you on which to found an opinion.