—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.