"In the upright systems the fruiting arms are either radiated from a low vine head, like the ribs of a fan, or they are taken off as horizontal arms from a central vertical trunk.
"Where the vineyard is not given close personal attention and pruning and other vineyard practices are neglected the best results will be obtained with the overhead trellis. Moreover, such a trellis permits cross-plowing and cultivation and is better adapted for grazing hogs, sheep, or cattle on cover crops grown in the vineyard. On the other hand, the careful vineyardist can expect the best and earliest results from vines on the upright or vertical supports. The upright trellis facilitates pruning, harvesting, spraying, and intercropping throughout the life of the vineyard; it is also easier to repair and can be erected from $10 to $20 an acre cheaper than the overhead trellis. The use of both the upright system and the overhead trellis has netted the growers profitable returns. Each has its advantages and disadvantages. The prospective grower, knowing his own conditions, must determine which training system is best suited to his conditions.
"During the first year after planting, a strong stake reaching 4 feet above the ground at each vine is sufficient support. A trellis should be erected the second season, though the upper wires of an upright trellis and the secondary wires of an overhead trellis may be added later, as the vines need them. In erecting an upright trellis the posts should be set midway between the vines, the distances apart varying with the distances between the plants. The end posts of the rows should be firmly braced. Three wires are generally used, placed 24, 42, and from 56 to 60 inches from the ground.
"In erecting an overhead trellis, the usual method is to place a substantial, durable post reaching 7 feet above the ground at each of the permanent vines. Rows of extra heavy, well-braced posts, running parallel with and also at the ends of the rows of vines, are set at the boundaries of the vineyard. There are a number of different ways of arranging the wires. Usually No. 10 galvanized wires are securely fastened to the tops of the boundary posts on the four sides of a vineyard and then are run along and securely fastened on the tops of the inside post down each row in both directions as governor wires. As needed, No. 14 wires 2 feet apart are run parallel with the governor wires until in this manner the entire area has been covered.
"A cheaper but less durable overhead trellis is made by running No. 9 governor wires in only one direction and the secondary wires only at right angles to the governor wires, the secondary wires being fastened to the governor wires wherever they cross.
"Some growers construct arbors entirely of wood, using slats or poles instead of wires.
"The pruning of Muscadine grapes during the first three years is mainly for the purpose of establishing the permanent parts and adjusting the other parts of the vine to the desired training system for future usefulness. After that the pruning is primarily a matter of renewing the bearing surface and keeping the vines healthy, vigorous, and productive.
"During the first season the trunk of the vine should be established. From this the main fruiting branches are started the second season. These, under favorable circumstances, will bear a small crop of fruit the third season. After that the purpose of pruning should be to renew growth, to increase or decrease the bearing surface, and to maintain the shape of the vine.
"Severe pruning usually removes most of the fruit-bearing wood and throws the vine into vigorous wood growth. No pruning, on the other hand, causes a growth which is too much distributed, weak, and incapable of bearing good crops. Therefore, the grape grower should study the vines sufficiently to enable him to judge each year the proper severity of pruning for the best results. This will depend on the variety, the age of the vines, the fertility of the soil, etc. Muscadine grapes bear their fruit in small clusters. It is therefore necessary to maintain a large fruiting surface in order to secure a proper tonnage of fruit. This is accomplished by developing a series of fruiting arms, spurring along these, and lengthening them as the vines become stronger. Such fruiting arms can be maintained for a number of years, but after a time it is desirable to renew them. This is done by cutting out the arm and starting a new one from a cane that has been previously grown for such purposes. It is preferable to renew systematically only one or, at most, two arms on a vine each year. This gradual renewal does not disturb the vigor of the vine, but keeps it productive, healthy, and strong. The pruning can be quickly and easily done if systematically practiced from the time the vines are started."
Rejuvenating Old Vines
When pruning and training are neglected, a vineyard soon becomes a sorry company of halt and maimed vines. These neglected vines can rarely be reshaped and restored to their pristine vigor. If the old vines seem capable of throwing out a strong new growth, it is almost always better to grow a new top by taking out canes from the roots and so rejuvenate. The energy and activity of Nature are seldom seen to better advantage than in these new tops, if the old tops are cut back severely and the vineyard given good care. The new canes grow with the gusto of the biblical bay tree, making it difficult oftentimes to keep them within bounds.
Usually this new top can be treated essentially as if it were a new vine. Not infrequently the cane will make sufficient growth and mature well enough so that it may be left as a permanent trunk at the end of the first season. If, however, the wood is short, weak and soft, it should be cut back in the autumn to two or three buds from one of which a permanent trunk can be trained the next season from which a good top can be formed in another season. The old top is discarded as soon as the new trunk is tied to the trellis. Old vineyards are often rejuvenated in this way to advantage and return profits to their owners for years; but if the soil is poor and the vines weak, attempts to renew the tops seldom pay.
Occasionally rejuvenating old vines by pruning is worth while. When such an attempt is made, it is best to cut back severely at the winter-pruning, leaving two, three or four canes, depending on the method of training, of six, eight or ten buds. The amount of wood left must depend on the vigor of the plant and the variety. The success of such rejuvenation depends much on selecting suitable places on the old vine from which to renew the bearing wood. It requires good judgment, considerable skill and much experience to rejuvenate successfully an old vineyard by remodeling the existing top, and if the vines are far gone with neglect it is seldom worth while.
Sometimes old vines or even a whole vineyard can be rejuvenated most easily by grafting. This is particularly true when the vines are not of the kind wanted, and when the vineyard contains an occasional stray vine from the variety to which it is planted. Directions for grafting are given on pages 45 to 50. The grafted vine is readily brought into shape, under any of the several methods of training, by treating it as a young vine.
CHAPTER IX
GRAPE-PRUNING ON THE PACIFIC SLOPE
The methods of pruning and training native grapes, discussed in the last two chapters, do not apply to the Vinifera grapes grown in the favored valleys of the Rocky Mountains and on the Pacific slope. As we have already seen, the Vinifera or Old World grape differs markedly in habits of growth from the American species so that it would not be expected that pruning which applies to the one would apply to the other types. The fundamentals, to be sure, are much the same and the different species of grapes are about equally subservient to the shears of the pruner, but while pruning to regulate fruit-bearing finds many similarities in Old and New World grapes, the training of the vines is radically different.
European practices in pruning and training Vinifera grapes are so many and so diverse that the first growers of this fruit in America were at a loss to know how to prune their vines. But, out of a half century of experience, American growers of Old World grapes have adapted from European practices and have devised to meet new conditions, methods which serve very well in the new home for this old grape. Since the culture of the Old World grape is centered in California, almost confined to that state, California practice may be taken as a pattern in pruning and training the vines of this species.
Vine Pruning in California[16]
The systems of pruning in use in California may be divided into two classes according to the arrangement of the arms on the trunk of the vine. In the commonest systems, there is a definite head to the trunk, from which all the arms arise symmetrically at nearly the same level. The vines of these systems may be called "headed vines." In the other systems, the trunk is elongated four to eight feet and the arms are distributed regularly along the whole or the greater portion of its length. The vines of these systems, owing to the rope-like form of the trunks, are called "cordons."
The headed vines are divided according to the length of the vertical trunk into high, 2–3 feet, medium, 1–11/2 feet, and low, 0–6 inches. The cordons may be vertical or horizontal, according to the direction of the trunk, which is from four to eight feet long. The horizontal cordons may be single (unilateral) or composed of two branches extending in opposite directions (bilateral). Double and even multiple vertical cordons occur, but they are very inadvisable and have no advantages.
The arrangement of the arms of a headed vine may be symmetrical in all directions at an angle of about 45 degrees. Such a vine is said to be "vase-formed," though the hollow center which this term implies is not essential. This is the form used in the great majority of our vineyards whether of wine, raisin, or shipping grapes. It is suitable for the "square" system of planting and cross cultivation. Where vines are planted in the avenue system, particularly when trellised and where cross cultivation is impossible, the arms are given a "fan-shaped" arrangement in a vertical plane. This arrangement is considered to be essential for the economical and easy working of trellised vines.
On the vertical or upright cordon, the arms are arranged at as regular intervals as possible on all sides of the trunk from the top to within twelve or fifteen inches of the bottom. On the horizontal cordon the arms are arranged similarly, but as nearly as possible on the upper side of the trunk only.
Each of these systems may again be divided into two subsystems, according to the management of the annual growth or canes. In one, spurs of one, two, or three eyes are left for fruit production. This system is called short or spur pruning. In the other, long canes are left for fruit production. This is called long or cane pruning. In rare cases an intermediate form is adopted in which long spurs or short canes of five or six eyes are left. In cane pruning, each fruit cane is accompanied by one or two short renewal spurs. These must also accompany half-long pruning. Systems of pruning, when only long canes are left without renewal-spurs, are not in use in California. In all systems, replacing-spurs are left wherever and whenever needed.
Other modifications are introduced by the manner of disposal of the fruit canes. These may be tied up vertically to a stake driven at the foot of each vine or bowed in a circle and tied to this same stake, or they may be tied laterally to wires stretching along the rows in a horizontal, ascending or descending direction.
The different systems differ therefore in: (1) the shape, length, and direction of the trunk; (2) the arrangement of the arms; (3) the use of fruit spurs or fruit canes with renewal spurs; (4) the disposal of the fruit canes.
The principal possibilities of the pruning are shown in the following table:
A. Head Pruning: Vase-form
| 1. High trunk: 2. Medium trunk: 3. Low trunk: |
with | (a) Fruit spurs or (b) Half-long canes and renewal spurs or (c) Fruit canes and renewal spurs; canes vertical or bowed. |
B. Head Pruning: Fan-shaped; Trellised
- 1. High trunk: Fruit canes and renewal spurs; canes descending.
- 2. Medium trunk: Fruit canes and renewal spurs; canes horizontal or ascending.
C. Cordon Pruning
- 1. Vertical: Spur; half-long; cane.
- 2. Horizontal-unilateral: Spur; half-long; cane.
- 3. Horizontal-bilateral: Spur; half-long; cane.
All possible combinations indicated by this table represent 24 variations. Some of these combinations, however, are not used and some are rare. The most common are shown in Figs. 23, 24, 25, 26 and 27.
Figure 23 B represents a headed, vase-formed vine, with a medium trunk and short fruit spurs. This is the most common system used in all parts of California and is suited for all small growing vines which bear on the lower buds, for most wine grapes and for Muscats. The unit of pruning in this case is a fruit spur of 1, 2, or 3 internodes, according to the vigor of the variety and of the individual cane.
Figure 23 A differs from 23 B only in the higher trunk and longer arms. It is commonly used for Tokay and other large growing varieties, especially when growing in rich soil and when planted far apart.
Figure 23 C has the same form of body as A and B, except that the arms are somewhat less numerous. The unit of pruning is a short fruit cane of four to five internodes, accompanied by a renewal spur of one internode. It is suited for vigorous table grapes, which do not bear well on short spurs. It is used especially for the Cornichon and Malaga in rich soil. This is a difficult system to keep in good shape owing to the tendency for all the vigor to go to the growth on the ends of the fruit canes. It is difficult to obtain vigorous canes on the renewal spurs. Occasional short pruning is usually necessary to keep the vines in proper shape.
Figure 24 A is similar to 23 C in form, but the number of arms is still further reduced to 2, 3, or at most 4. The unit of pruning is a fruit cane of 21/2 to 31/2 feet with its renewal spur. Owing to the length of the fruit canes they require support and are tied to a high stake.
This method is used in a large number of vineyards with Sultanina, Sultana and certain wine grapes, especially Semillon and Cabernet. It is not to be recommended in any case, as it has several very serious defects.
The difficulty of obtaining new wood from the renewal spurs is even greater than in the system shown in Fig. 23 C. The length and vertical position of the fruit canes cause the main growth and vigor of the vine to be expended on the highest shoots. The renewal spurs are thus so shaded that, even though their buds start, the shoots make but a weak growth. The result is that at the following pruning all the good new wood is at the top of the fruit canes of the previous year, where it cannot be utilized. The pruner has to choose then between reverting to spur pruning and getting no crop or using the weak growth from the renewal spurs for fruit canes, in which case he may get blossoms but little or no fruit of any value.
Other defects of this method are that the fruiting shoots are excessively vigorous and therefore often tend to drop their blossoms without setting and the fruit when produced is massed together so that it ripens unevenly and is difficult to gather. It also requires a tall and expensive stake.
Figure 24 B represents an improvement on the last system. It differs only in the method of treating the fruit canes. These are bent over in the form of a circle and tied by their middle part to a stake which may be smaller and lower than that needed for the vertical canes.
This bowing of the canes has several useful effects. The change of direction moderates the tendency of the vigor of the vine to expend itself only on the terminal shoots. More shoots therefore are formed on the fruit canes and as their vigor is somewhat decreased they tend to be more fruitful. The slight mechanical injury caused by the bending operates in the same direction.
The excess of vigor thus being diverted from the fruit canes causes the renewal spurs to form vigorous shoots, which soon grow above the fruit shoots and obtain the light and air they need for their proper development. This method is used successfully for certain wine grapes such as Riesling, Cabernet, and Semillon. It is unsuited to large vigorous varieties or for vines on rich soil planted wide apart. In these cases two fruit canes are usually insufficient and, if more are used, the grapes and leaves are so massed together that they are subject to mildew and do not ripen evenly or well. The bowing and tying of the canes requires considerable skill and care on the part of the workmen.
The body, arms, and annual pruning of the system shown in Fig. 25 are similar to those of Fig. 24, with the exception that the arms are given a fan-shaped arrangement in one plane. It differs in the disposal of the fruit canes, which are supported by a trellis stretching along the row from vine to vine.
This method is largely used for the Sultanina (Thompson's Seedless), and is the best system for vigorous vines which require long pruning, wherever it is possible to dispense with cross cultivation. It is also suitable for any long-pruned varieties when growing in very fertile soil.
Figure 26 is a photograph of a four-year-old Emperor vine, illustrating the vertical cordon system. It consists of an upright trunk 41/2 feet high with short arms and fruit spurs scattered evenly and symmetrically from the top to within fifteen inches of the bottom. This system is used in many Emperor vineyards in the San Joaquin Valley.
Its advantages are that it allows the large development of the vine and the large number of spurs which the vigor of the Emperor demands, without, on the one hand, crowding the fruit by the proximity of the spurs or, on the other hand, spreading the vine so much that cultivation is interfered with. It also permits cross cultivation.
One of its defects is that the fruit is subjected to various degrees of temperature and shading in different parts of the vine and the ripening and coloring are often uneven. A more vital defect is that it cannot be maintained permanently. The arms and spurs at the top of the trunk tend to absorb the energies of the vine and the lower arms and spurs become weaker each year until finally no growth at all is obtained below. After several years, most of the vines therefore lose their character of cordons and become simply headed-vines with abnormally long trunks.
The cordon can be reëstablished in this case by allowing a vigorous sucker to develop one year from which to form a new trunk the next. The following year the old trunk is removed entirely. An objection to this method is that it makes very large wounds in the most vital part of the vine—the base of the trunk.
Figure 27 is a photograph of a four-year-old Colombar vine, illustrating the unilateral, horizontal cordon system. It consists of a trunk about seven feet long, supported horizontally by a wire two feet from the ground. Arms and spurs are arranged along the whole horizontal part of the trunk.
This system accomplishes the same objects as the vertical cordon. It allows a large development of the vine and numerous fruit spurs without crowding. It is superior to the vertical cordon in the distribution of the fruit, which is all exposed to approximately the same conditions owing to the uniform distance from the ground of the fruit spurs. All parts of the trunk producing an annual growth of wood and fruit are equally exposed to light and the tendency of the growth to occur principally at the part of the trunk farthest removed from the root is counteracted by the horizontal position. There is not the same difficulty therefore in maintaining this form of vine permanently that there is with the vertical cordon.
This system should not be used for small weak vines, whether the weakness is a characteristic of the variety or due to the nature of the soil. It is suited only to very vigorous varieties such as Emperor, Almeria, and the Persian grapes when growing far apart in rich, moist soil.
Periods of development.
The first year in the life of a vine is devoted to developing a vigorous root system; the next two or three years to building up a shapely trunk and head, and a like period to forming the full complement of arms. At the end of from five to nine years the framework of the vine is complete and should undergo no particular change of shape except a gradual thickening of trunk and arms.
There are, therefore, several periods in the life of the vine with varying objects, and the methods of pruning must vary accordingly. These periods do not correspond exactly to periods of time, so it may be misleading to speak of pruning a two-year-old or a three-year-old vine. One vine under certain conditions will reach the same stage of development in two years that another will reach only in three or four years under other conditions. The range of time of these periods is about as follows:
| First period—Formation of a strong root system | 1 | to | 2 years |
| Second period—Formation of stem or trunk | 1 year | ||
| Third period—Formation of head | 2 | to | 3 years |
| Fourth period—Complete development of the arms | 2 | to | 3 years |
| Total time of formation of framework | 6 | to | 9 years |
Under exceptionally favorable conditions the first and second periods may be included in the first year and a completely formed vine may be obtained in five years.
Before planting.
For planting, cuttings, one-year-old rooted vines, or bench grafts are used. In all cases, they need some attention from the pruner.
The usual way to prune a good rooted vine of average size having a single cane at the top and several good roots at the bottom is to shorten the cane to one or two buds and the roots to two or four inches, according to their size. Shortening the cane makes the vine less liable to dry out before rooting and forces the growth from the lower buds which produce more vigorous shoots. The roots are shortened so that there will be no danger of the ends being turned upwards when planted. If they are to be planted in a large hole, they may be left as long as five or six inches; if to be planted with a crowbar or dibble, they must be cut back to half an inch.
If the rooted vine has several canes, all but one should be removed entirely, and this one shortened to one or two eyes. The one left should be that which is strongest, has the best buds, and is the best placed. Where a horizontal cane is left, it should be cut back to the base bud. Otherwise the main growth may occur at a higher bud and the vine will have a crook which will result in a badly formed trunk.
If canes are growing from different joints, it is usually best to leave the lower cane if they are equally vigorous. This brings the buds from which growth will come nearer to the roots, and leaves less of the original cutting, which are advantages. The upper joint between the canes is, moreover, often more or less decayed or imperfect.
First growing season.
The treatment during the first spring and summer will depend on what growth the vines are expected to make and on whether the vines are staked the first year.
With cuttings and with both rooted vines and grafts where the growth will be moderate, staking the first year is unnecessary, though it has some slight advantages. In these cases, no pruning of any kind is necessary until the winter following the planting, except in the case of bench grafts. The pruning in the last case is confined to the removal of the suckers from the stock and roots from the cion. If the stocks have been well disbudded by the nurseryman, few suckers will develop. In moist soil, the cion roots may develop vigorously and must be removed before they grow too large, or they may prevent the proper development of the resistant roots.
The removal of roots should usually be done some time in July. For this purpose the hill of soil is scraped away from the union and after the cion roots and suckers are removed it is replaced. In this second hilling up, the union should be just barely covered so that the soil round the union will be dry and unfavorable to a second growth of roots. Later in the season, about September, the soil should be removed entirely from around the union and any new roots that may have formed removed. The union is then left exposed to harden and mature, so that it will pass the winter without injury.
First winter pruning.
At the end of the first growing season, an average good vine will have produced from three to five canes, the longest of which will be from two to three feet long.
Soon after the leaves have fallen in December or early in January the vines should be pruned. The method is precisely similar to that used for rooted vines before planting except that the main roots are not touched. All the canes are removed entirely except one. This one should be well matured, at least at the base, and should have well-formed eyes. It is shortened to two eyes. It is well also to cut off all shallow roots within three or four inches of the surface. This is necessary in the case of grafted vines if any have escaped the summer root-cutting.
Some of the vines may have made an exceptionally large growth. Such vines may sometimes possess a cane large enough from which to start the trunk in the way described later for the second winter pruning.
Staking.
If the vines have not been staked before, the stakes should be driven soon after pruning and before the starting of the buds.
In order to preserve the alignment of the vineyard, the stakes should be driven on the same side of every vine at a uniform distance. The best distance is about two inches. If driven closer they may injure large roots or even the main underground stem if the vines have not been carefully planted vertically or slanting towards the side on which the stake is to be placed.
The side on which the stake should be placed depends on the direction of the prevailing winds during the growing season. This side is the leeward. That is, the stake should be so placed that the wind will press the vine towards the stake instead of away from it. This will much facilitate the work of keeping the vine upright and attached to the stake. If the vine is on the other side the pressure of the wind will stretch the string tight and the swaying of the vine will gradually wear the string until it breaks, necessitating retying. By carefully observing this rule, very few vines will require retying even if weak material like binding twine is used.
Second summer pruning.
Before the starting of the buds, in the spring following the planting, most of the vines appear about the same as when they were planted. There is, however, a very notable difference, in that they have well-developed root systems in the soil where they were formed. The result is that they make a much more prompt and early start and will produce a much larger growth than they did the first season. For this reason they require very careful attention from the pruner during the spring and summer of the second season. Vines neglected at this time, in this respect, may make as large a growth, but a large part of it will be wasted, the vines will be misformed and it will require from one to two years longer to develop a suitable framework and to bring them into bearing, even though they are properly handled during subsequent years. The more vigorous the vines, the more necessary it is to handle them properly during this period.
The main object during this second growing season is to develop a single, strong, vigorous and well-ripened cane from which to form the permanent trunk of the vine.
This is done by concentrating all the energies of the vine into the growth of a single shoot. As soon as the buds start, or when the most precocious has developed a shoot of a few inches in length, the vines should be disbudded. This consists in rubbing off with the hand all buds and shoots except the two largest and best placed. The lowest, upright shoots are usually the best. Leave only those which will make a straight vine. It is better to leave less developed buds than a shoot which, when it grows, will make an awkward crook with the underground stem.
After this disbudding, the two shoots left will grow rapidly, as they receive all the energies of the root system. When the longest have grown from ten to fifteen inches, they should be tied to the stake. Unless this is done, they are liable to be broken off by any heavy wind, owing to their soft, succulent texture. Only the best placed and most vigorous of the two shoots should be tied up. If this shoot is growing upright and near the stake, this can be done without any danger of injuring it. In this case the second shoot should be removed. If the shoot has to be bent over in tying it to the stake it may be injured. In such a case the second shoot should be allowed to grow until it is known whether the first has been injured. In case of injury the second shoot can be tied up the next time the vines are visited and the injured shoot removed.
At the tying up of the reserved shoots, all new shoots which have developed since the first disbudding should be removed. The shoots should be tied up loosely, as they are soft and easily injured, and they should be brought around carefully to the windward side of the stake.
The shoots will require tying once more when they have grown another foot or eighteen inches. There will then be two ties, one at two or three inches from the top of the stake and the other at about the middle. If the vines have a tall stake and are to be headed very high, another tying higher up may be needed later.
With vines making only a moderate growth, no other pruning will be needed until the winter. Exceptionally vigorous vines, however, may make a cane eight, ten or more feet long. Such a cane is heavy and is very likely to break the ropes by which it is attached to the stake. In this case it may break off at the bottom, or at least will form an awkward crook near the ground when it matures. In either case it is difficult to form a good trunk the following year. Even when the ties do not break, the cane will not be well suited for the commencement of a trunk, as the joints will be so long that it will be impossible to leave enough well-placed buds at the winter pruning.
Both these difficulties are avoided by timely topping. When such vigorously growing canes have grown twelve or eighteen inches above the top of the stake they are cut back about level with the stake. This is most conveniently done with a long-bladed knife or piece of split bamboo. After topping, the cane ceases to grow in length and laterals start at most of the joints. It is less exposed to the action of the wind, and the laterals supply the buds needed for forming the vine at the winter pruning.
The result of the second season's growth, then, has been to produce a single vigorous cane with or without laterals. This is the cane which is to develop into the final and permanent trunk of the vine. It must not only be large and vigorous, but must be properly matured. If the vine is allowed to grow too late in the season, an early frost may destroy the unmatured cane, and much of the results of the year's growth will be wasted. Such a frost may indeed kill the entire vine. Grafted vines are particularly liable to injury from this cause, as if they are killed down to the union they are completely ruined. Ungrafted vines when killed to the ground may be renewed from a sucker next year. This sucker, however, is likely to grow with such vigor that it is even more liable to injury from an autumn frost than the original shoot.
This late growth is much more likely to occur with young vines than with old. The old vines stop growing earlier because their energies are directed into the crop, and as they produce a larger amount of foliage they draw more upon the moisture of the soil, which therefore dries out earlier.
Late growth of the young vines must be prevented and the wood matured before frost if possible. This is accomplished by means which promote the drying of the soil in autumn. Late irrigations should be avoided. Cultivation should usually stop by midsummer. In very moist, rich soils, it is often an advantage to grow corn, sunflowers or similar crops between the rows of vines to take off the surplus moisture. In some cases it is good practice to let the summer weeds grow for the same purpose.
Second winter pruning.
With vines which have been treated as described and to which no accident has happened, the second winter pruning is very simple. It consists simply in cutting back the single cane which has been allowed to grow to the height at which it is desired to head the vine.
The vine so pruned consists of a single cane which with the older wood at the base reaches nearly to the top of the stake, or fifteen inches. This if properly treated will develop into a vine with a trunk of about twelve inches, though this length can be modified slightly, as will be explained later.
This cane consists of about seven or eight joints or internodes, with an equal number of well-formed eyes and an indefinite number of dormant buds, principally near the base of the cane or junction of the one- and two-year-old wood. Only the buds on the upper half of this cane will be allowed to grow. These buds—about four—should give six to eight bunches of grapes and four, six, or eight shoots from which to form the spurs at the following winter pruning.
With a vine which has been cut back to form a high head, the cane is about twenty-four inches long and can be used to form a trunk eighteen inches high, though this height can be modified as in the last case. As with the shorter cane, only the buds on the upper half will be allowed to produce shoots. These—about six—should give ten to twelve bunches and the shoots necessary for the formation of spurs.
In all cases a full internode has been left above the top bud. This is done by cutting through the first bud above the highest which it is desired to have grow. This cut is made in such a way as to destroy the bud but to leave the diaphragm intact and part of the swelling of the node. This upper internode is left partly to protect the upper bud, but principally to facilitate tying. By making a half-hitch around this internode, the vine is held very firmly. If the swelling at the node of the destroyed bud is not left, many vines will be pulled out of the hitch when they become heavy with leaves and supple with the flow of sap in the spring.
In tying the vines, no turns or hitches must be made around any part except this upper internode. A hitch below the top bud will result in a crook-necked vine, as the top will bend over in the summer under the weight of the foliage. A hitch lower down is even more harmful, as it will girdle and strangle the vine.
A second tie about half way from the upper to the ground is always necessary to straighten the cane. Even if the cane is straight when pruned, a second tie is needed to keep it from curving under the pressure of leaves and wind in the spring. For high-headed vines three ties are usually necessary.
For the top tie, wire is particularly suitable. It holds better than twine and does not wear. Even though it is not removed, it does no harm, as the part around which it is wound does not grow. The lower ties should be of softer material, as wire has a tendency to cut into the wood. They should be placed so that the cane is able to expand as it grows. With thin and especially with round stakes this means that the tie must be loose. With large, square stakes there is usually sufficient room for expansion, even when the twine is tied tight.
Third summer pruning.
During the third season, average well-grown vines will produce their first considerable crop and develop the canes from which will be formed the first arms.
Such a vine, soon after the starting of the buds in spring, will have one vigorous shoot about three inches long grown from the old wood and five fruit buds started above on the cane. All the buds and shoots below the middle of the cane should be removed.
This will leave the four or five fruit buds and will give the vine the opportunity to produce eight or ten bunches of grapes. These buds will produce also at least four or five shoots. If the vine is very vigorous and the season favorable, they may produce eight, ten or more.
When the five shoots grow, the height of the head will be determined at the next winter pruning by which of the corresponding canes are left as spurs. If the highest two canes are cut back to spurs and all others removed, the vine will be headed as high as possible, as these two spurs form the two first arms which determine the length of the trunk. If the lowest two canes are chosen and all of the vine above them removed, the trunk will be made as low as possible. Intermediate heights can be obtained by using some other two adjacent canes and removing the rest. It is often advisable to leave some extra spurs lower than it is desired to head the vine and to remove these lower spurs the following winter after they have borne a crop. For example, the three or four upper canes might be left, if the vine is vigorous enough, and the lowest one or two of these removed at the next pruning. This, however, is not often necessary with properly handled vines and is objectionable because it makes large wounds in the trunk.
Third winter pruning.
At the end of the third season's growth the vine should have a straight, well-developed trunk with a number of vigorous canes near the top from which to form the arms.
Figure 28 represents a well-grown vine at this period. No shoots have been allowed to grow on the lower part of the trunk and the five buds allowed to grow above have produced nine vigorous canes. The pruner should leave enough spurs to supply all the fruit buds that the vine can utilize. The number, size and thickness of the canes show that the vine is very vigorous and can support a large crop. It will depend somewhat on the variety how many buds should be left. For a variety whose bunches average one pound, and which produces two bunches to the shoot, twelve fruit buds should give about twenty-four pounds, or about seven tons per acre, if the vines are planted 12 by 6 feet, as these were. The number of spurs will depend on their length. Six spurs of two buds each will give the required number, but as some of these canes are exceptionally vigorous they should be left a little longer, in which case a smaller number of spurs will suffice.