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.
In a hardwood cutting of lemon verbena all leaves are taken off, in zonale geraniums from the open ground few if any are left, in coleus and verbena about one half are removed, while in Olea fragrans, Daphne odora, and heath, only enough for planting. Use a sharp knife; but scissors are handy for trimming and sometimes for making cuttings of those small-wooded plants which root easily.
Fig. 1163. Propagating-box.
Fig. 1165. Small propagating-box, adapted to a window.
The cuttings of plants with milky juice should be washed before planting. Sometimes the lower ends are allowed to dry for several hours, the tops being protected against wilting. Large and succulent cuttings, e. g., of pineapple, cotyledon and cactus, should be dried before planting by letting them lie on the surface of the propagating-bed for several days, or they may be planted in dry sand at first. Under these conditions a callus forms which tends to prevent decay; but the wood must not shrivel.
Peter Henderson has introduced a method which is likely to increase the percentage of rooted plants, and which is desirable in slow-growing varieties, like the tricolor geraniums. He advises that the cutting should be partly severed and allowed to hang to the parent plant for a few days; this results in a partial callus or even roots, before the cutting is entirely removed.
In planting cuttings, use a dibble or open a V-shaped trench. Never thrust the cutting directly into the soil. Plant deep enough to hold the cutting upright and no deeper (as in Fig. 1171), making due allowance for the sand settling; the distance apart should be just enough to prevent them from pressing against each other. It must be remembered that they stay in the bed only until rooted. As soon as growth begins, they are potted off. When the cuttings are inserted, the sand should be firmly pressed about them, and they should be watered with a syringe or with a fine rose; the forcible application of water compacts the sand, thus excluding air, .and prevents undue wilting.
Give shade immediately, using lath shutters outside, cloth screens or papers placed directly on the cuttings within, and attend to this very carefully for the first few days. Lift the shades early in the afternoon, and put them on late in the morning, but keep them on during the middle of the day, thus gradually accustoming them to full light.
Cuttings should never suffer from dryness. The sand should always be kept moist to the verge of wetness. Ventilation should be given on bright days, but all exposure to draft avoided. A good temperature for propagating is from 60° to 65° F., increasing these figures for tropical plants and reducing them for more hardy kinds. It is debatable whether bottom heat and confined air are advisable for cuttings of growing wood. The older gardeners employed both, but now neither is commonly used, except for tropical plants, like croton, or when a constant succession of crops of cuttings is required. There is no doubt that with this aid cuttings will root more quickly, but more skill and care are required, neglect bringing on fungous disease, which results in unhealthy plants or total loss. If bottom heat is used, the average temperature of the bed should be 10° or so above that of the air, but less will suffice. Indeed, in beds made as described above, in good weather the sand is enough warmer than the greenhouse atmosphere to answer every purpose.
If a confined air is wanted, ventilation and shading must be carefully looked after, and precautions taken against the accumulation of condensed moisture within the bell-glass or frame.
Fig. 1166. Cutting of soft growing wood, (as of Coleus.)
Fig. 1164. Propagating-box or hood.
Fig. 1167. A rooted verbena cutting.
Fig. 1168. A geranium cutting.
Fig. 1169. A rose cutting.
Although it is tender plants, in the main, that are propagated by cuttings of growing wood, the above methods can be practised advantageously with some hardy plants. The wood, which is invariably more successful if hardened, is obtained either from plants forced for this purpose, e. g., spirea, Deutzia gracilis, or it is gathered in June and July out-of-doors, e.g., lilac, hydrangea. They should be potted off in 2- or 3-inch pots, in a rather sandy soil, when the roots are from 1/4 to 1/2 inch long. It is sometimes good economy to box them, i.e., plant them a few inches apart in flats, when not immediately required.
Some hardy perennials, like Phlox subulata, Campanula carpatica, Gentiana acaulis and the hardy candytuft, can also be easily increased in this way. Make the cuttings 2 to 3 inches long and plant in flats or pots in sand or a sandy soil in October, November or December, before any hard frost. Keep in a coolhouse and pot off when rooted. They make nice plants for planting out the following spring. Plants of this same nature can also be propagated in the open air in autumn. Make the cutting longer, 6 inches when possible, and do the work earlier, in September or in August in some cases.
Fig. 1170. Hardened-wood cutting of dahlia.
Fig. 1171. A carnation cutting.
Fig. 1172. Hardwood cutting of currant.
Cutting of ripened or dormant wood. Figs. 1172-1174.
Many plants grow readily from twigs of the year's growth taken in fall or winter or very early spring. The "soft-wooded" plants usually propagate most readily by this means. These cuttings of mature wood may be either long or short.