Granadilla (Passiflora edulis, etc.). Passifloreæ.
Propagated by seeds, or, less easily, by cuttings.
Grape (Vitis, several species). Vitaceæ.
Grape seedlings are very easily grown. If the ground is fit and there is no danger from vermin, the seeds may be sown in the fall, but they are usually stratified and sown in spring. They come readily if sown out-doors, but some prefer to force them under glass with a mild bottom heat. Seedlings do not “come true,” and they are therefore grown only for the purpose of obtaining new sorts.
The grape is very readily multiplied by layers, either of the ripe or green-wood. The ripe wood or canes may be layered either in fall or spring, but spring is usually chosen. The cane is simply covered up two or three inches deep, and nearly every bud will produce a plant. In August or September the layer should be lifted and cut up into plants. Better plants are obtained if only the strongest canes are used and only a part of the buds on each are allowed to grow. The cane is usually cut back to four or five buds, or if very strong plants are desired only one bud is left on each layer. Canes of the previous year, those recently matured, are preferred, although wood two or three years old may be used, but in this case it is usually necessary to cut or otherwise wound the joint in order to induce the formation of roots. Vines or stools grown for the production of layers should be cut back severely in fall or winter, to induce a vigorous growth of canes the following season. These canes are then layered the succeeding fall or spring. Only a part of the canes are layered from any stool, a part being allowed to grow for cutting back the next fall in order to get another crop of canes. In some varieties which do not strike readily from cuttings, layering is considerably practiced by nurserymen. The Delaware is often grown in this way. Extra strong layers can be secured by layering in pots. A large pot, filled with rich soil, is plunged beneath the layer. In this manner a layer may be rooted and separated even while carrying fruit. Layering in pots is employed only in special cases.
Green-layering is sometimes practiced upon new and scarce varieties, but strong plants are not obtained unless they are well handled by forceful culture after they are separated. The growing cane is layered in mid-summer, usually by serpentine layering.
Cuttings are usually employed by nurserymen to propagate the grape. These are made in many fashions. In all ordinary cases hard-wood cuttings are made from the ripened canes in autumn or winter when the vines are pruned. It is advisable to take the cuttings before the canes have been exposed to great cold. Select only those canes which are well-matured, solid and rather short-jointed. In common practice, the cuttings are cut into two-bud length, the lower cut being made close to the bud. The cuttings will range from six to ten inches in length. Some prefer three-bud cuttings ([Fig. 43]), but unless the cane is very short-jointed such cuttings are too long to be planted and handled economically. Three-bud cuttings usually give stronger plants the first season because roots start from both joints as a rule. Very strong plants are obtained from mallet cuttings ([Fig. 45]), but as only one such cutting can be made from a cane, unless the cane bears very strong branches, they are not much used. Various methods of peeling, slitting and slicing cuttings are recommended, in order to extend the callusing process but they are not used in common or commercial practice. The cuttings are tied in bundles of 50 or 100, and stored in sand, moss, or sawdust in a cellar, until spring, when they are planted in rows in the open. Some varieties, of which the Delaware is an example, do not strike readily from cuttings. Some growers start common cuttings of these under glass in spring. Others bury the bundles of cuttings in a warm exposure in the fall, with the butt ends up and about level with the surface of the ground. This affords bottom heat to the butts and induces callusing. At the approach of cold weather the cuttings are removed to a cellar, or are heavily mulched and allowed to remain where buried. Storing is safer. Some growers obtain the same results by burying upside down in a cellar. These slow-rooting sorts often start well if they are simply kept in a warm cellar—but where the buds will not swell—all winter, as the callusing is then hastened. At the end of the first season the plants may be transplanted. The plants are often sold at this age, but buyers usually prefer two-year-old plants.
Single bud or “eye” cuttings are largely used for the newer and rarer varieties. These are cut from the canes in the fall, the same as long cuttings, and are stored in boxes of sand or moss. A month before the weather becomes settled, these boxes may be taken into a house or greenhouse, or put in a mild hot-bed, to induce the formation of the callus. They may then be planted out-doors, and a fair proportion of most varieties may be expected to grow. The best and commonest way of handling eyes, however, is to start them under glass. They are planted horizontally or nearly so and about an inch deep in sand or sandy earth in a cool greenhouse in late winter—in February in the northern states—and in about six weeks the plants will be large enough to pot off or to transplant into cold-frames or a cool house. If only a few plants are to be grown they may be started in pots. When the weather is thoroughly settled, they are transferred to nursery rows, and by fall they will make fine plants. There are various ways recommended for the cutting of these eyes—as cutting the ends obliquely up or down, shaving off the bark below the bud, and so on—but the advantages of these fashions are imaginary. A good eye-cutting is shown in [Fig. 50]. The foreign grapes are propagated by eyes in the north.
Soft cuttings are sometimes used to multiply new kinds. These may be taken in summer from the growing canes, but the plants are usually forced during winter for the purpose of giving extra wood. Cuttings are taken off as fast as buds form during the winter, and they are forced in close frames with a good bottom heat. The cuttings may comprise two buds, with the leaf at the upper one allowed to remain, or they may bear but a single eye, in which case the leaf, or the most of it, is left on. This rapid multiplication from small, soft wood usually gives poor plants; but strong plants may be obtained by allowing the wood to become well hardened before it is used. Soft cuttings will root in two or three weeks under good treatment.
In order to secure extra strong plants from single buds, the eyes may be saddle-grafted or whip-grafted upon a root two or three inches long. The root-grafts are then treated in the same way as eye cuttings, only that they are usually grown in pots from the start.