Fig. 7. A cutting beginning growth.
The cuttings are planted as soon as the ground is warm and dry enough to work. To delay planting too long invites injury from drought, which almost annually parches the land in eastern America. Irrigation gives more leeway to planting time in the West. When warm sunny weather, accompanied by an occasional shower, predominates, the cuttings start growth almost at once, as shown in [Fig. 7], and by fall, all things being propitious, make a growth from four to six feet. With the cuttings three inches and the rows three feet apart, 58,080 vines may be grown to the acre.
Single-eye cuttings.
New and rare varieties are propagated from single-eye cuttings, thereby doubling the number of plants from the propagating wood. This method gives an opportunity, also, to start the work of propagating early in the season, since single-eye cuttings are nearly always rooted by artificial heat. But the greatest value of the method is that some varieties which cannot be propagated in any other way readily grow under artificial heat from single-eyes. Well-grown vines so propagated are as good as those grown by any other method, but the great disadvantage is that unless much care and skill are used, vines from these cuttings are poor and quite worthless. It is also a more expensive method than growing from long cuttings out of doors.
There are several ways of making single-eye cuttings. The most common form of the cutting is the single bud with an inch of wood above and below, the ends being cut with a slant. Some modify this form by cutting away the wood on the side opposite the bud, exposing the pith the whole length of the cutting. In another form, a square cut is made directly under the bud, leaving an inch and a half of wood above. Or this last form is modified by making a long sloping cut from the bud to the upper end, thereby exposing the maximum amount of cambium. Advantages are claimed for each form, but these are mostly imaginary, and the cutting may be made to suit the fancy of the propagator if a few essentials are observed.
Single-eye cuttings are made in the fall and are stored in sand until late winter, about February in New York. At this time the cuttings are planted horizontally an inch deep in a sand propagating bench in a cool greenhouse. If the cuttings are not well calloused, they remain one or two weeks in a temperature of 40° to 50° without bottom heat, but well-made cuttings are calloused and ready to strike root so that brisk bottom heat can be applied at once. After six weeks or two months, the young plants are ready to pot off or to transplant in a cold-frame or cool greenhouse. If but a few plants are to be grown, they may be started in two- or three-inch pots, shifting into larger pots once or twice as growth progresses. In early summer, the young plants are set in nursery rows out of doors and by fall the young vines should be strong and vigorous.
Single-eyes are also started in hot-beds, cold-frames and even in the open air without the aid of artificial heat. In hot-beds and cold-frames, the method is only a modification of that described for greenhouses. Out of doors the cuttings are given the same conditions under which long cuttings are rooted, except that the whole of the short cutting is buried an inch deep in the nursery row.
Herbaceous Cuttings
Grapes are easily propagated from herbaceous cuttings, although since the vines are weak and the method expensive, they are seldom used. Green cuttings are usually taken from plants forced in greenhouses, but may be taken in summer from vineyard vines. A green cutting is usually cut with two buds with the leaf at the upper one left on. The cuttings are set in propagating beds of sand, or pots of sand, in close frames under which there is brisk bottom heat. To prevent excessive evaporation, the frames are kept closed and the atmosphere warm and moist. As growth progresses, or if mildew appears, the frames are more and more ventilated. In two to four weeks, the cuttings should have rooted sufficiently well to be transplanted to pots. Herbaceous cuttings made in the summer must be kept under glass until the following spring.