Manual of American Grape-Growing Part 3

CHAPTER III

PROPAGATION

The grape commends itself to commercial and amateur growers alike by its ease of propagation. The vines of all species may be propagated from seed, and all but one of the several cultivated species may be grown readily from cuttings or layers. All yield to grafting of one kind or another. Seeds are planted only to produce new varieties. At one time stocks were grown from seed, but this practice has fallen into disrepute because of the great variations in the seedlings.

Varieties on their own roots and stocks are for most part propagated from cuttings. In the production of stocks, the viticulturist sets the orchardist a good example, for there can be no question that all tree-fruits suffer from being grown on seedling stocks. The grape is a vigorous, self-a.s.sertive plant and once it is started, whether from seeds, cuttings or layers, seldom fails to grow.

SEEDLINGS

Growing seedling grapes is the simplest of operations. The seeds are taken from the grapes at harvest time, after which they must pa.s.s through a resting period of a few months. At once or in a month or two, the seeds should be stratified in moist sand and stored in a cold place until spring, when they may be sown in flats or in the open ground; or seed may be sown in a well-prepared piece of garden land in the autumn. When planted in the open, autumn or spring, the seeds are put in at the depth of an inch, an inch or two apart and in rows convenient for cultivation. Subsequent care consists of cultivation if the seed are sown in garden rows, and in p.r.i.c.king out when true leaves appear if planted in flats. In ground that crusts, an expedient is to mix grape seed with apple seed; the apple seedlings, being more vigorous, break the crust and act as nurse plants to the more tender grapes. Sometimes it is helpful to the young plants to mulch the ground lightly with lawn clippings or moss. Grape seedlings grow rapidly, often making from two to three feet of wood in a season.

The young plants are thinned or set to stand four or five inches apart in the nursery row. At the end of the first season, all plants are cut back severely and almost entirely covered with earth by plowing up to the row on both sides. This earth, of course, is leveled the following spring. If the seasons are propitious and all goes well, the seedlings are ready for the vineyard at the end of the second season, but if for any reason they have fared badly during their first two years, it is much better to give them a third season in the nursery. Seedling vines are seldom as vigorous as those from cuttings, and unusual care must be taken in setting in the vineyard, though the operation is essentially the same as that to be described for vines from cuttings.

The third season the vines are kept to a single shoot and are pinched back when the canes reach a length of five or six feet. In the autumn, they are pruned back to two or three feet. In the spring of the fourth season, the trellis is put up and a few fruits may be allowed to ripen.

The vines of promise may now be selected. The plants, however, must fruit twice or oftener before it can be told whether hopes are consummated or must be deferred. Growing seedlings for new varieties is a game full of chances in which, while there may be little immediate or individual gain, there is much pleasure. It is hardly too much to say that the grape industry of eastern America, with its 300,000 acres and 1500 varieties, betokens the good that has come from growing seedling grapes.

DORMANT CUTTINGS

Vines for vineyards, with the exception of varieties of Rotundifolia, are propagated from cuttings of hard wood taken from the season's canes when the vines are pruned. The inactive buds in these cuttings may be brought into active growth, and roots induced to grow from the cut surfaces by various means. By this miracle of Nature, an infinite number of plants, in an endless procession, may be propagated from the product of a single seed, each plant complete in its heredity and differing from its fellows only in accordance with environment.

_Time to make cuttings._

A good cutting should have a protective callus over the cut and this requires time, so that the sooner cuttings are made after the wood becomes thoroughly dormant the better. Besides, the cutting should use its stored food material for the formation of advent.i.tious roots rather than have it pa.s.s into buds, as it quickly does late in the dormant season when buds are about to open. If cuttings must be made late in the season, transplanting must be delayed as long as possible, and the cuttings be set in a northerly aspect to prevent the premature development of the buds. However, the grape responds surprisingly well to the call of Nature in forming roots, and great importance need not be attached to the time at which the cuttings are made.

_Selecting cutting wood._

Cuttings are made from one-year-old wood; that is, canes produced during the summer are taken for cuttings in the fall. Immature canes and those with soft, spongy wood ought not to be used. Strong vigorous canes should be given preference over weak growth, but most nurserymen maintain that very large canes do not make as good cuttings as do those of medium size, the objection to large size being that the cuttings do not root as well. Short-jointed wood is better than long-jointed. Cuttings from vines weakened by insects and fungi are liable to be weak, soft, immature and poorly stored with food. The wood should be smooth and straight.

_Making the cutting._

Grape cuttings vary in length from four inches to two feet, the length depending on the climate and the soil of the nursery and the species and variety. The hotter and drier the climate and the lighter the soil, the longer the cutting needs to be. Six to nine inches, however, is the usual length in the climate of eastern America, while on the Pacific slope the length varies from eight to fifteen inches. For convenience in handling, all cuttings should be approximately of the same length, to insure which some kind of simple gauge is needed.

Various gauges are used, as marks cut in the working table, a stick of the required length, or a cutting-box.

In making the cuttings, a slanting cut is made close below the lowest bud, while about an inch of wood is left above the upper bud. When possible, a heel of old wood is left at the lower end; or, still better, a whorl of buds, as roots usually start from each bud. The finished cuttings are tied in bundles, all b.u.t.ts one way, and are then ready to be heeled-in. This is done by burying in trenches, b.u.t.ts up, and covering with a few inches of soil. It is important to invert the cuttings in trenching, since otherwise the tops often start to grow before the b.u.t.ts are properly calloused, and it is very essential that the tops remain dormant until roots appear to support the new growth.

_Planting the cuttings._

Cuttings are planted in the nursery in rows wide enough apart for cultivation and two or three inches apart in the row. Trenches are made with a plow; perpendicular if the cuttings are shorter, and a little slanting if longer than six inches. The cuttings are set at a depth which permits the upper buds to project above the ground, as shown in Fig. 6. When the cuttings in a row are placed, two inches of soil are put in and pressed firmly about the base of the cuttings.

Then the trench is evenly filled with earth and the cultivator follows. Doing duty by the young plants consists in cultivating often during the summer to keep the soil moist and mellow.

[Ill.u.s.tration: FIG. 6. Planting cuttings.]

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.

[Ill.u.s.tration: FIG. 7. A cutting beginning growth.]

_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 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 establishing 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._