Part 10 (1/2)
Fruit-bearing may be augmented by bending, twisting or ringing the canes, since all of these operations diminish vegetative vigor.
Ringing is the only one of these methods in general use, and this only for some special variety or special purpose, and usually with the result that the vigor of the vine is diminished too much for the good of the plant. Ringing is discussed more fully in Chapter XVI.
_The manner of fruit-bearing in the grape._
Before attempting to prune, the pruner must understand precisely how the grape bears its crop. The fruit is borne near the base of the shoots of the current season, and the shoots are borne on the wood of the previous year's growth coming from a dormant bud. Here is manifested one of Nature's energy-saving devices, shoot, leaves, flowers and fruit spring in a short season from a single bud. In the light of this fact, pruning should be looked on as a simple problem to be solved mathematically and not as a puzzle to be untangled, as so many regard it. For an example, a problem in pruning is here stated and solved.
A thrifty grape-vine should yield, let us say, fifteen pounds of grapes, a fair average for the mainstay varieties. Each bunch will weigh from a quarter to a half pound. To produce fifteen pounds on a vine, therefore, will require from thirty to sixty bunches. As each shoot will bear two or three bunches, from fifteen to thirty buds must be left on the canes of the preceding year. These buds are selected in pruning on one or more canes distributed on one or two main stems in such manner as the pruner may choose, but usually in accordance with one or another of several well-developed methods of training. Pruning, then, consists in calculating the number of bunches and buds necessary and removing the remainder. In essence pruning is thinning.
_Horizontal_ versus _perpendicular canes._
An old dictum of viticulture is that the nearer the growing parts of the vine approach the perpendicular, the more vigorous the parts. The terminal buds, as every grape-grower knows, grow very rapidly and probably absorb, unless checked, more than their share of the energy of the vine. This tendency can be checked somewhat by removing the terminal buds, which also helps to keep the plants within manageable limits, but is better controlled by training the canes to horizontal positions. Grape canes are tied horizontally to wires to make the vines more manageable and to reduce their vigor and so induce fruitfulness; they are trained vertically to increase the vigor of the vine.
_Winter-pruning._
Winter-pruning of the vineyard may be done at any time from the dropping of the leaves in the autumn to the swelling of the buds in the spring. The sap begins to circulate actively in the grape early in the spring, even to the extremities of the vine, and most grape-growers believe this sap to be a ”vital stream” and that, if the vine is pruned during its flow, the plant will bleed to death. The vine, however, is at this season of so dropsical a const.i.tution that the loss of sap is better denominated ”weeping” than ”bleeding.” It is doubtful whether serious injury results from pruning after the sap begins to flow, but it is a safe practice to prune earlier and the work is certainly pleasanter. The vine should not be pruned when the wood is frozen, since at this time the canes are brittle and easily broken in handling. On the other hand, it is well to delay pruning in northern climates until after a heavy freeze in the autumn, to winterkill and wither immature wood so that it can be removed in pruning.
[Ill.u.s.tration: PLATE IX.--Campbell Early (2/3).]
_Summer-pruning._
There are three kinds of summer-pruning, the removal of superfluous shoots, heading-in canes to keep the vines in manageable limits and the pruning to induce fruitfulness discussed on a foregoing page, which need not have further consideration. It is very essential that the grower keep these three purposes in mind, especially as there is much dispute as to the necessity of two of these operations.
All agree that the vine usually bears superfluous shoots that should be removed. These are such as spring from small, weak buds or from buds on the arms and trunk of the vine. These shoots are useless, devitalize the vine, and hinder vineyard operations. A good practice is to rub off the buds from which these shoots grow as they are detected, but in most vineyards the vines must be gone over from time to time as the shoots appear. Still another kind of superfluous shoots, which ought to be removed as they appear, are those which grow from the base of the season's shoots, the so-called secondary or axillary shoots. These are usually ”broken out” at the time the shoots from weak buds are removed.
While there is doubt as to the value of heading-back the vine in the summer for the sole purpose of inducing fruitfulness, there can be no doubt that it is desirable for the purpose of keeping some varieties within bounds. Heading-back is not now the major operation it once was, the need of severe cutting being obviated by putting the vines farther apart, by training high on three or even four wires and by adopting one of the drooping systems of training. The objections to heading-back in the summer are that it often unduly weakens the vines, that it may induce a growth of laterals which thicken the vines too much, and that it delays the maturing of the wood. These bad effects, however, can be overcome by pruning lightly and doing the work so late in the season that lateral growths will not start. Most vineyardists who keep their plantations up find it necessary to head back more or less, depending on the season and the variety. The work is usually done when the over-luxuriant shoots begin to touch the ground. The shoots are then topped off with a sickle, corn-cutter or similar tool.
RENEWING FRUITING WOOD
There are two ways of renewing the fruiting wood on a grape-vine, by canes and from spurs. The manner of renewing refers to pruning and not to training, for either can be used in any method of training.
_Cane renewals._
Renewal by canes is made each year by taking one or more canes, cut to the desired number of buds, to supply bearing shoots. By this method the most of the bearing wood is removed each year, new canes taking the place of the old. These renewal canes may be taken either from the head of the vine or from the ground, though the latter is little used except where vines must be laid down for winter protection. Canes may be renewed indefinitely, if care is exercised in keeping the stubs short, without enlarging the head from which the canes are taken out of proportion to the size of the trunk. Renewing by canes is a more common method than renewal by spurs, as will be found in the discussion of methods of training.
[Ill.u.s.tration: FIG. 13. Vine ready for pruning; _i_, the stem; _g_, arms; _d_, canes; _s_, shoots; _b_, spurs. The faint lines near the bases of the canes indicate the points where they should be pruned off in the winter, leaving spurs for the production of shoots the following season.]
_Spur renewal._
In renewing by spurs, a permanent arm is established to right and left on the canes. Shoots on this arm are not permitted to remain as canes but are cut back to spurs in the dormant pruning. Two buds are left at this pruning, both of which will produce bearing shoots; the lower one, however, is not suffered to do so but is kept to furnish the spur for the next season. The shoot from the upper bud is cut away entirely. When this process is carried on from year to year, the spurs become longer and longer until they become unwieldy. Occasionally, however, happy chance permits the selection of a shoot on the old wood for a new spur. Failing in this, a new arm must be laid down and the spurring goes on as before. The objections to renewing by spurs are: it is often difficult to replace spurs with new wood, and the bearing portion of the vine gets farther and farther from the trunk. For these reasons, spur-renewing is generally in disfavor with commercial grape-growers, though it is still used in one or two prominent methods of training, as will be discovered in this discussion. Figure 13 shows a vine ready for pruning.
THE WORK OF PRUNING
The pruner may take his choice between several styles of hand pruning-shears with which to do his work. The knife is seldom used except in summer-pruning, and here, more often, the shoots are broken out or pinched out. In winter-pruning, the cane is cut an inch or thereabout beyond the last bud it is desired to leave; otherwise the bud may die from the drying out of the cane. The canes are usually allowed to remain tied to the wires until the pruning is done, though growers who use the Kniffin method of training may cut them loose before they prune. Two men working together do the work of pruning best. The more skilled of the two severs the wood from the bearing vine, leaving just the number of buds desired for the next season's crop. The less skilled man cuts tendrils and severs the cut canes from each other so that the prunings may be moved from the vineyard without trouble by the ”stripper.”
Not the least of the tasks of pruning is ”stripping” the brush and getting it out of the vineyard. The prunings cling to the trellis with considerable tenacity and must be pulled loose with a peculiar jerk, learned by practice, and placed on the ground between the rows.
Stripping is done, usually by cheap labor, at any time after the pruning until spring, but must not be delayed until growth starts or the young buds may suffer as the cut wood is torn from the trellis.
The brush is hauled to the end of the row by hand or by horse-power applied to any one of a dozen devices used in the several grape regions. One of the best is the device in common use in the Chautauqua vineyards of western New York. A pole, twelve feet long, four inches in diameter at the b.u.t.t and two at the top, is bored with an inch hole four feet from the b.u.t.t. A horse is. .h.i.tched to this pole by a rope drawn through the hole, and the pole, b.u.t.t to the ground, is then pulled between rows, the small end being held in the right hand. The pole, when skillfully used, collects the brush, which is dumped at the end of the row by letting the small end fly over towards the horse.