Part 3 (2/2)
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, s.h.i.+fting 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 gla.s.s until the following spring.
LAYERING
The grape is readily propagated from layers of either green or mature wood, the method being certain, convenient and producing extra vigorous plants. The drawback is that fewer plants can be obtained by layering than from cuttings with a given amount of wood. Varieties of some species, however, cannot be propagated by cuttings, and with these layering becomes of supreme importance to the propagator. Nearly all varieties of Rotundifolia and some of aestivalis are best grown from layers. So far as is known, all varieties of cultivated species may be grown by layering, and since the method is simple and certain and the vines vigorous and easily handled, this method is commended to small growers of grapes.
_Dormant wood layering._
The work of layering mature wood usually begins in the spring, but the vines from which the layers are to be taken should have received preliminary treatment the preceding season. The vines to be layered are severely cut back a year or more before the layering is to be done to induce a vigorous growth of canes. Strong vigorous canes are laid in a shallow trench, two to five inches deep, in which they are fastened with wood or wire pegs or staples. The trench is then partly filled with fine, moist, mellow earth which is firmly packed about the cane. Roots strike and shoots spring from each joint. When the young plants are well above ground, the trench is completely filled, and then, or a little later, the young plants are staked to keep them out of the way of the cultivator. The following fall the young vines are ready to transplant.
The essentials of layering have been given, but a number of non-essentials may be helpful under some conditions. Thus, dormant wood may be layered in the fall, in which case the cane is usually notched or ringed at the joint to induce the formation of roots. The less the number of joints covered, the stronger the young vines, so that while the number is usually five, six or more extra vigorous plants may be obtained by covering only one or two joints. In propagating Rotundifolia grapes, it is expected that lateral branches will make the tops of the new plants. These, at the time of layering, are cut back to eight or ten inches, all on the same side of the vine, and are not left closer together than twelve inches. In nursery practice, Rotundifolia vines are trained along the ground for layering. Vines on arbors, in greenhouses, or on sides of buildings are easily layered in boxes or pots of soil. Plants grown from layers are not as conveniently handled as those from cuttings.
_Green wood layering._
Layered plants from green wood are sometimes grown to multiply quickly new or rare varieties. The work is accomplished in midsummer by bending down and covering shoots of the present season's growth.
Strong plants are seldom obtained from summer-layering and it is never safe to attempt to grow more than one or two plants from a shoot. The most forceful culture possible must be given summer-layered plants after the separation from the parent vine. It is very generally agreed that plants from summer-layers not only do not give good plants, but that the parent vine is injured in taking an offspring from it in this way.
_Layering to fill vacancies in the vineyard._
There is sure to be an occasional gap even in the best vineyard. Young plants set in vacancies must compete with neighboring full-grown vines, and often in a bit of land so unfavorable that it may have been the cause of the demise of the original occupant. Under these circ.u.mstances, the newcomer stands a poor chance for life. A plant introduced by layering a strong cane from a near-by vine has little difficulty in establis.h.i.+ng itself on its own roots, after which it can be separated from the parent. Such layering is best done by taking in early spring a strong, unpruned cane from an adjoining plant in the same row and covering an end joint six inches deep in the vacant place, but leaving sufficient wood on the end of the cane to turn up perpendicularly out of the soil. This free end becomes the new plant and by the following fall or spring may be separated from its parent.
Not infrequently the young plant bears fruit the second season on its own roots. This method is of especial value in small plantations, whereby the trouble of ordering one or two plants is avoided and the advantage of early fruiting is obtained.
GRAFTING
Since grafting grapes is intimately connected with stocks, the growing of which is a modern practice, grafting is thought of as a new process in growing this fruit. Quite to the contrary, it is an old practice.
Cato, the st.u.r.dy old Roman grape-grower who lived nearly two hundred years before Christ, speaks of grafting grapes, although Theophrastus, the Greek philosopher, wrote a hundred years before ”the vine cannot be grafted upon itself.” However, until it became necessary to grow Vinifera grapes on resistant stocks to avoid the ravages of phylloxera, grafting the grape was not at all common among vineyardists and is not now except where vines susceptible to phylloxera must be grown in consort with roots resistant to this insect, or to modify the vigor of the top by a stock more vigorous or less vigorous. For these two purposes, grafting is now in some grape regions one of the most important vineyard operations.
In grafting the grape, there is a time and a way, not so particular as many believe, but rather more particular than in grafting most other fruits. If the essentials of grafting are kept in mind, one has considerable choice of details. Grafting consists in detaching and inserting one or several buds of a mother plant on another plant of the same or a similar kind; the bud stock is the cion, the rooted plant is the stock. The essentials may be set forth in three statements: First, the prime essential is that the cambium layers, the healing tissue lying between the bark and wood, meet in the cion and stock; second, that method of grafting is best in which the cut tissues heal most rapidly and most completely; third, the greater the amount of cambium contact, as compared with the whole cut surface, the more rapidly and completely the wounds will heal. Out of a great many, the following are a few of the simplest methods in use in grafting the grape, any one of which may be modified more or less as occasion calls.
_Vineyard grafting in eastern America._
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