This section is from the book "The Standard Cyclopedia Of Horticulture Vol2", by L. H. Bailey. See also: Western Garden Book: More than 8,000 Plants - The Right Plants for Your Climate - Tips from Western Garden Experts.
Tender plants require the same or a little higher temperature than that in which they thrive.
In sweet potato, the tuber is cut lengthwise and laid, with the cut side down, on moist sand or moss, the edges being slightly covered. Buds develop on these edges and are removed when of proper size and treated as cuttings of growing wood, or allowed to remain until rooted. In dracena (see Fig. 1052, page 842)-and this applies to stem- as well as root -cuttings - the buds are not taken off until rooted the original cutting remains in the sand and sometimes produces a second or even a third crop. The tuberous rootstock of Arum macula-tum, and plants of like nature, can be cut into pieces, remembering that the bud-producing portion of arum is the top, and each part will grow successfully. Exercise care in watering and maintain a good temperature.
Fig. 1174. Short cuttings of ripened wood.
Fig. 1175. Root-cutting of blackberry. (X 1/3)
The rootstocks of cannas are cleaned and cut into pieces 1 1/2 to 2 inches long and planted in a warmhouse in February (Fig. 784, p. 657). As soon as buds push and roots form they are potted off and grown until the season for bedding out. Dahlias are not, properly speaking, propagated from rootstock, but by division; the plant cannot produce adventitious buds. There must always be a bit of the crown attached to the tuber. The propagation of dahlias so closely resembles the methods here described that it is perhaps well to mention it.
Root-cuttings for planting in the open ground are made from 4 to 6 inches long, and are planted firmly in V-shaped trenches or furrows in spring, being covered 2 inches or more deep. Roots as large as one's little finger are chosen, and good results are secured with plants of vigorous growth. In plants like lily-of-the-valley, common lilac, calycanthus, Scotch and moss roses, unless short of stock, it is better to encourage the natural growth of the suckers and propagate by division, but they all can be multiplied as above described.
Variegation, curiously enough, is not always reproduced by means of root-cuttings.
Many leaves are capable of producing roots. Some have the further power of developing buds after rooting, and of these last a few furnish an economical means of bud-propagation, particularly when the stem growth is insufficient. In cotyledon (eche-veria) the whole leaf is used, the smaller ones from the flower-stalk being often the best. Choose those that are fully matured, and dry them for a few days on sand, but do not let them shrivel. The treatment, otherwise, is as given above for cuttings of growing wood. In gloxinia and other Gesneraceae, the whole leaf (Fig. 1176), half a leaf, or even a lesser portion, is used. When enough clear petiole is obtainable, no further preparation is needed. When a part only of the leaf is planted, some of the blade must be cut away. As a rule, no bud is developed the first season: a tuber is formed, which will grow in due time.
The common Begonia Rex is increased by leaves in various ways. The whole leaf may be planted as a cutting, keeping the petiole entire or cutting it off where it unites with the blade; or the whole leaf may be pinned or "weighted to the surface of moist sand (Figs. 501-503, p. 470), and, if the principal veins are severed at intervals of an inch, a plantlet will appear at every cut. The best way is to divide the leaf into somewhat triangular pieces, each part having a strong vein near the center. Plant in sand, in good temperature, and treat precisely as if they were cuttings of growing wood. Roots and buds will soon grow, and a good plant will result within a reasonable time. Pot off when roots are 1/4 inch long. Certain other begonias may be similarly multiplied.
The thickened scales of bulbs, like lilies, can be used for propagation. Remove the scales intact and plant upright, like seeds, in soil made of equal parts of sand and rotted leaf-mold (Fig. 1177). September and October are the usual months for this work. If they are kept in a cool greenhouse, the young bulblets will appear in the course of the winter, but top growth will come later, in summer. This is a slow, laborious process, and is seldom practised except in propagating new varieties. The granular scales of achimenes and plants of like nature can be used for propagating, sowing them in a sandy soil as seeds are sown; but this method is not a good one in ordinary cases. The scales of Zamia horrida have been made to produce new plants, as have also the tunicated scales of an amaryllis.
Fig. 1176. Leaf-cutting of gloxinia.
Fig. 1177. Lily scale producing bulblets.
For further details of cuttage, consult Lindley's "Theory and Practice of Horticulture," 2d ed.; Burbidge, "The Propagation and Improvement of Cultivated Plants;" Peter Henderson's "Practical Floriculture;" Bailey's "Nursery-Book."
B. M. Watson.