PRUNING.
Winter Pruning, or Pruning Hard Wood.
—The pruning of vines comprises two different processes. The first one has for its object the shaping of the vines, the second one similarly the shortening of the branches properly so as to enable them to bear better fruit. These two points must always be kept in view, much more so of course during the first few years, before the vines have reached their bearing age. But even in after years the pruning must be so conducted, that the shape of the vine is not changed so as to interfere with the work in the field, or with the perfect development of the grapes. As regards the shape of the vine, it has been decided that in our raisin districts the Muscat requires to be pruned low, in order to properly protect the grapes from sun and wind. The head should be as low as possible, or even rest on the ground, and in no instance be more than a few inches above the same. Many of the bunches will then rest on the ground or hang a few inches above it, and experience shows us that such low bunches are the best and those which produce the finest raisins. Tall Muscat vines never produce as sweet and as large bunches or grapes as those headed low, and their grapes are apt to sunburn or be otherwise checked in their growth. During the first year, the young vine should be cut back to a single stem, it being enough to leave two or three eyes above the ground. The second season these canes should all be cut away except three, which are to form the future head of the vine. Each one of these may be cut to two eyes, thus leaving six eyes on the vine. In the majority of vines, the head should by this time have been formed, as the following year will be the first year in which the vines will bear.
When Muscat vines have grown two seasons, they should be pruned for fruit. The third season will always give some fruit, while, in many localities where the vines have been well cared for, the yield may be quite large and pay handsomely. No direction as to pruning, which will apply to every locality or to every vine, is possible. In different localities the climatic and other conditions are so variable that the methods of pruning may be modified. Where the vines grow strong and vigorous more wood should be left. In cool and sheltered places the vines should be given a greater spread to allow more sun and air to enter. In warm localities, with a broiling sun, the principal object in pruning should be to properly shelter the grapes. There is danger, or at least there are great disadvantages in pruning either too long or too short, and in leaving too many or too few spurs. In pruning too long, or leaving too many eyes, the shape of the vine is changed or even seriously injured. In leaving too many spurs, the vines may bear too many and too small grapes. To find the medium between these extremes is always the great object and study to which the grower should devote his attention. In rich and moist soils which produce strong vines, more eyes should be left, and in sandy, poor soil a few eyes may suffice to cause the vine to bear much more that it can properly mature and perfect. The year before the vines bear their first good crop, the spurs left should not exceed three or four, and each spur should not have more than two eyes, including the eye nearest the old wood, which eye is often overlooked and not counted in. The next year a few more spurs may be left, but at no time should each spur be allowed to carry more than two eyes. If more eyes are left, the lower eyes will not develop, and the only thing attained by such pruning is to increase the size of the head, and to place the leaves and the grapes farther away from the center of the vine.
At the age of six years, or when the vine is in full bearing, no more spurs should be added, as the vine has then attained a mature age, and the yield will increase independently of an increased number of spurs. How many spurs should be left it is not possible to say. The experience with most growers is generally that too few spurs are left, and that from ten to fifteen spurs are not too many on large and healthy vines. The tendency of the growers is now to leave more spurs than formerly, and to always restrict the spurs to two eyes each. This experience has been acquired simultaneously in Fresno, San Bernardino and San Diego counties. Many growers affirm the fact that the difficulty is to get spurs enough, and my own experience is that, after the vine has once attained its age of full bearing, all the strongest branches are required to furnish spurs, and that only the weak and sickly shoots should be cut away entirely. The strong flow of sap in the spring requires many outlets, so as not to unnecessarily push the cell walls and cause disorders, and in case the soil is not strong enough to sustain and perfect so many grapes, it is better to manure it heavily and make it rich enough for all purposes. I believe an average of from eight to ten spurs are required by strong and bearing vines. Only strong canes should be left at any time. Weak and immature canes should be cut off close to the trunk or to the head.
Muscatel Vine Eight Years Old, after Winter Pruning.
This method of pruning differs materially from that this season adopted by A. B. Butler. He leaves now only from five to eight spurs on the vines, generally the lesser number. He maintains that his object is to produce large and superior grapes, and not to have his vines overbear. The outcome of such close pruning has not yet been demonstrated, but it may be possible that this is the proper way. Mr. Butler has certainly one point in his favor, and that is that it has not yet been demonstrated that very close pruning causes the disease known as black-knot, as quite frequently the unpruned vines show this disease much more than those which are pruned close. Another point in favor of this pruning is that it has been practiced in Malaga for years without any ill effects. But, before such very close pruning can be generally recommended, our experience in this direction should be more extensive, and several years more will be necessary to come to any satisfactory conclusion in this respect. We know, however, that too many (say from twenty to twenty-five) spurs will exhaust the low-headed Muscatel vines, and in order to bring such vines back to proper bearing it has been found necessary to reduce the number of spurs at once to one-third and then gradually increase their number as the vines grow stronger. Every grower should study his own vines and adapt the number of spurs to the quality of the crop. If the crop is inferior, reduce the number; if again the crop is superior, we may try to gradually give a few more spurs in order to reach the greatest yield of first-class grapes. In pruning the spurs, the cut should be made a little above the eye or bud, and not so close to it that it will be injured and dry out.
Suckers from the roots should be removed to a limited extent, that is, now and then a sucker may be left in order to give material for forming a new head, if this should be found necessary. But as a rule the many suckers which rise from the roots should be removed in early spring with a sharp-pointed stick, and even those which rise from below the regular head should be broken off while young, or be pruned off in winter time.
Another system of pruning called the Chaintre system has been introduced, or at least spoken of during the last few years. As, however, it is not generally used, or even to my knowledge used at all, for raisin grapes, I need only here allude to it. It consists of pruning the vine to one single long stem, which is carried along the ground and, at a distance of six or eight feet from the root, fastened to a stake. This branch is pruned to shorter branches and spurs, each of the latter to one or two eyes each to furnish wood and fruit. The advantages of the Chaintre pruning are claimed to be principally two,—a greater yield of grapes and a larger outlet for the abundant sap in the spring. It is supposed that, if the vine is pruned too short, the sudden flow of sap in the spring has a great tendency to poison some of the cells and vessels of the wood, and cause the disease known as black-knot. The Chaintre system endeavors, by furnishing the vine with more cells and vessels, and thus a larger outlet for the sap, to overcome this difficulty. The Chaintre system has, however, some great inconveniences. It interferes considerably with the tillage of the soil. It increases the cost of the vineyard through the extra stakes necessary to support the vines,—inconveniences so great that I doubt whether the system will ever be seriously adopted anywhere on this coast, even if it should prove of any advantage.
The time for the pruning depends upon the season. The only safe rule is that vineyards may be pruned as soon as the vines are dormant. If pruned too soon, a new growth will start, which will be killed by the first frost. In many seasons the pruning may be done in November and December; in large vineyards it must be begun early, so as to finish before the plowing commences. Early pruning will cause the vines to start early in the spring, while late pruning will considerably delay the starting of the buds. When the spring frosts are to be feared, the pruning may be deferred for some months, or until the end of January, as it delays the budding out of the vine in the spring, sometimes as much as fourteen days. But, on the other hand, the first warm spring weather is so favorable to the development of the grapevines and the setting of the fruit, that every advantage should be taken of the same. The very best crops are generally had on early pruned vines.
Bleeding of the Vines.
—The bleeding of the vines after pruning in the spring is by many considered injurious. So far as I know, no direct experiments to prove this have been made in this country, but European experiments with wine grapevines point to no ill effects from the bleeding of the vines. The bleeding retards the budding out, and this fact has led some growers to the practice of pruning twice. In the first pruning an extra eye is left on every spur, and these eyes are again clipped off shortly before the eyes begin to swell in the spring. The bleeding of the vines thus causes the eyes to be retarded until the frost is over. I believe such practice is both unnecessary and too costly, and is not required in any of our raisin districts, and where such practice must be employed the raisin grape cannot be perfectly at home. Of late years spring frosts have become very rare in our principal raisin districts, and the practice of double pruning is no longer thought of.
Summer Pruning, or Pruning Green Wood.
—Summer pruning is a much disputed vineyard operation, which, however, at least in some localities, is of great importance. This summer, or rather spring, pruning consists of cutting back the young growing shoots from one-third to one-half just after the berries have set well. The proper time of the year is in May, but the exact time must necessarily be different in different localities and seasons. In Fresno the cutting back should not be done later than May, and never except when the vines show a vigorous growth. The principal object the summer pruner has in view is to force the secondary branches of the vine as much towards the center of the vine as possible, so as to form there a perfect canopy of shade to serve as a protection to the young and tender berries. If let alone, the branches of the vine will throw out these secondary shoots near the top of the branches, thus leaving the head of the vine unprotected from the sun. The shortening in of the branches necessarily throws the new shoots to the center of the vine. A not less important object to be sought by the summer pruning is the strengthening of the young branch. In May, when the vines are covered by the young and vigorous shoots, they are yet exceedingly brittle, and only a slight pushing is required to break the branch off just at its junction with the old wood. A heavy wind at this time sometimes does an immense damage, and the vineyard will look as though every vine had been dragged over. Half of the branches may be broken and hang partially attached to one side of the vine. A single wind may ruin two-thirds of the crop. This can only be prevented by the summer pruning of the vines. By a heavy shortening in of the branches, the latter expose so much less surface for the wind to act on, that no branches are broken, and we have failed to see the heaviest wind cause any noticeable damage in vineyards which had their vines properly shortened in. The summer pruning in no way injures the vines. The sap is checked in its flow only for a few days, and within a week the new side shoots make their appearance. But the vineyardist must be careful not to summer prune after the hot summer weather has set in, as the hot weather will burn or scald the young grapes and ruin them entirely. For the San Joaquin valley raisin districts, I cannot advise summer pruning after the first days of June; in Southern California, somewhat later. Grapevines on sandy, dry and poor soil should not be summer pruned, or only very lightly so. They have not strength to start a new growth and will remain stunted all through the season.
Many growers of Riverside, El Cajon and Fresno consider summer pruning beneficial, if not necessary, and practice it every year regularly. It is necessary to summer prune heavily or not at all. Cut back one-half of the growth, or cut back leaving one or two leaves above the bunch of grapes on every cane. If the young canes are only topped, the secondary branches will come out near the ends of the canes and bear them down, in time exposing the bunches to the sun as well as causing the second crop to grow too far from the main trunk, the summer pruning thus acting the opposite of which it was intended. In Greece the wine grapevines are summer pruned, but the currants are never so treated.
Root-pruning.
—The pruning of the roots of grapevines, in order to cause them to bear, is entirely unnecessary, and is never done by experienced growers. Some growers have practiced the cutting of the surface roots of the vines so as to cause the tap roots or the main roots to go farther down, and they claim that by this method greater crops are harvested. I am satisfied this is only a theory not supported by facts. Surface roots are as necessary to plants as deep-soil roots, and serve the plants in their way, bringing atmospheric air to the circulation in the roots. If too many surface roots are formed, it is a sure indication of too much water in the top soil, as too frequent irrigation with a small stream of water will cause such roots to form. The proper remedy is to irrigate less frequently, but more at a time. The above does not refer to the pruning of the roots of grafted vines. In cases where Muscats have been grafted on resistant stocks, it is of importance that the graft should not make roots of its own, as these would soon overpower the stock and in their turn succumb to the enemies which it was the intention to avoid. When rooted vines are planted in the vineyard, their roots should be well pruned, and all dead and decaying, as well as dried-up, parts should be removed. If they are allowed to remain on the vines, they will draw moisture from the sound parts at a time when all the moisture is needed for the formation of new roots.
Suckering.
—The object of this process is to relieve the raisin-vine of superfluous wood before the latter has had time to draw on the strength of the vine and deprive it of the elements necessary to support the fruit-bearing branches. The proper time for suckering is early in the spring, when the young wood is yet tender and easily broken. With a hard and flat piece of wood, the lower suckers are dug out from below the ground, while the upper suckers may be broken by hand. A sucker must be understood to be any branch which does not produce fruit at a time when the vine is old enough to bear. In strong and moist soil and on strong vines even the lowest shoots produce grapes, and can therefore hardly be called suckers. But as a rule even they should be removed, unless we have a special object in view, such as renewing the trunk of the vine, lowering its head, or in otherwise encouraging the lower branches.
While few vineyardists take sufficient care and time to sucker their vines, there can be no doubt that the operation is of the greatest importance, in order that as large and good a crop as possible may be secured. It is not only best to remove all the non-fruit-bearing branches which spring out from the root and the trunk, but also a little later on, after the shoots have reached a foot or more, to cut any branch from the head of the vine which does not produce fruit. In many instances, however, it is necessary to renew the head of the vine, and for that purpose lower suckers may be allowed to grow. For a year or two these are pruned regularly and made to bear, and the old sickly head is then removed.