Manual of American grape-growing

by U. P. Hedrick

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 Æstivalis 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 circumstances, 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 sturdy 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.