All fruits, ornamental trees, and shrubs that will sprout from the surface-roots naturally or by wounding with plow or spade will grow from root-cuttings. Indeed, some trees not known to sucker, such as the hackberry, have been found to grow readily from properly kept root-cuttings.
The cuttings are made four inches long late in autumn and packed away in boxes, mingled with sand, which are kept over winter in the cellar. In planting in early spring the advice is usually given to cut the roots shorter and plant horizontally in shallow trenches; but this applies to root-cuttings in cold frames, or with bottom heat. In planting in the open air long experience has shown the best results and most even stand from planting in a shallow trench with one sloping side, as shown in Fig. 15
In filling, the earth is pounded in tightly to firm the cuttings, covering about one inch over the upper end of the root-cutting. Planted in this way the upper buds will push upward and the lower ones will form roots sooner on account of moisture four inches below the surface.
Boot-cuttings will usually grow if planted wrong end up, but growth is retarded and not as certain as when in natural position. With a little practice the one who places the cuttings can tell at a glance the top end by the fibres (17. How Seedling-roots Grow).
In the South, root-cuttings are usually planted as soon as made, but at the North it is best to start callusing and bud-development in the cellar. An outdoor dirt-covered cave is best for storage, as the temperature and moisture are better under control.
Many of the roses not easy to grow from ripe or green wood cuttings, such as Rosa rugosa and its hybrids, can be grown from root-cuttings.
Where tree-seeds are not easily obtainable, as with the hackberry, trees can usually be grown from root-cuttings.
The rose, lilac, juneberry, flowering almond, barberry, and other shrubs do not sucker, but throw out subterranean sprouts from the crown. Cuttings can be made from the subterranean sprouts, which can be treated the same as those made from surface-roots.