The following information on grape pruning and grape training comes from Five Acres and Independence by M. G. Kains. Five Acres and Independence is also available to purchase in print.
Grapes will thrive on every kind of soil that will grow other cultivated crops and be more likely to yield better under adverse conditions than any other fruit. They require less space than even the smallest standard fruit tree; in fact, the area usually allowed in business orchards for a mature peach tree (20′ x 20′) is greater than necessary for six vines as grown in eastern commercial vineyards. The flowers open late in spring so are more likely than those of other fruits to escape frosts.
Trained as described further on vines may begin to bear the year after planting; when managed according to usual commercial practice a year longer is usual. I have repeatedly gathered as much as six pounds of fruit from strong vines planted only 17 months before and 25 to 30 pounds the year after. With ordinary care vines are likely to yield abundantly for 25 years at least. On one farm that I owned is a Concord vine 45 years old that averaged more than half a bushel of fruit a year, though it had been so neglected that when I bought the place I cut out a small wagon-load of dead and worthless wood and the former owner said the vine would die! But it bore that year and every year while I owned the place.
Red, “white” and blue varieties cover a great range of flavors from mid-August to October without storage and when properly stored to March or even April. Some varieties are especially delicious as dessert, some adapted to jelly, jam or conserve, others for juice or wine. Various European varieties grown in California make raisins. No fruit plant is easier to train or so adaptable to all sorts of situations and styles of support. No matter how little your present experience you may count upon being successful after learning two fundamental principles and may grow choicer grapes than are usually sold in the markets and stores.
Having decided upon varieties suited to your locality order the vines as early in the year as possible so as to get the kinds you want. First class one-year vines are generally better than those two years old and far better than still older ones which not only cost more but are slower to bear fruit because of the loss of roots. On arrival handle them as suggested for other nursery stock. (Chapter 33.)
Give the vines the best soil and the sunniest site at your disposal. When the soil is poor or the site trying (as against a building) dig a hole as wide as a washtub and somewhat deeper for each vine, throw a peck or more of bones in the bottom and fill the hole with good soil before planting. The bones will supply plant food as they decay.
After the plants are planted cut off all puny shoots and shorten the strongest stem of each to only two or three joints with a plump bud at each. This will concentrate the plant food so the new shoots will be sturdier than if all or a larger number of buds were left to grow.
As soon as the strongest shoot gets woody at its base (in early summer) shorten the weak ones to only one joint and one leaf. Until then it may be easily broken off; hence the advisability of leaving two or three shoots temporarily. By allowing each of the temporary ones to retain one joint and one leaf after cutting them back, the main stem will not be wounded and drying or dying will be avoided. In this method of treatment lies the secret of gathering fruit the year after planting—but on only strong vines.
Fruit is borne on the green shoots and on no other or older part. The shoots develop from buds formed in the angles of the leaf stems. Where the growing season is short these buds are developed during the previous summer. They are conspicuous during winter at the joints on one-year-old canes. Occasionally similar buds may appear on older wood but these may be disregarded except when it is desired to have new branches or trunks develop to take the place of old, decrepit or diseased ones where these buds are located. Sometimes a second or even a third set of shoots may develop and even bear fruit in a single season but the fruit will not ripen unless the season is long enough.
Most pruning and training depend upon the use of buds formed the previous year. From these arise green shoots which consist of joints, leaves, tendrils and flower clusters from which last the fruit is developed. The tendrils and the flower (or fruit) clusters present gradations between themselves thus proving that one is a modification of the other.
Each green shoot has one chance—only one—to bear fruit. If it fails it never has another; the buds it bears take up this function and produce fruit on their green shoots.
Because only green shoots bear the fruit, the fruit-bearing parts of untrained vines get farther and farther away from the roots each year. The result is that each successive year the vine wastes unnecessary amounts of energy and plant food in pumping sap from roots to leaves and elaborated food back from leaves to roots so that in nature and neglected vines little or no fruit is produced. This is where man steps in and compels the vine to produce liberally by pruning off parts that have survived their usefulness. He reduces the distance between root and branch and forces the vines to focus their attention upon fruit production. The removal of excess parts also conserves plant food so that the clusters of fruit are larger and the berries both bigger and of improved quality.
When these two principles are understood and acted upon, grapevines will produce abundant high quality fruit every year no matter how their parts are placed on supports. However, when trained upon posts the fruit is often injured by being whipped about by wind. So this method should usually be avoided.
Two kinds of canes are worthless—puny shoots often found on young, weak, neglected and very old vines; and “bull” canes, the thick, long-jointed, burly fellows that often grow 20′ in a single season. The canes that produce best are those of medium diameter—about the thickness of an ordinary lead pencil.
On arbors and summer houses more work is required to prune the vines than by any other method of training. Unless special care is taken to develop and train branches low down on the sides such structures will become bare below and the roofs too densely: overgrown. Thus most of the fruit can be reached only with a ladder and pruning will be a tedious and difficult task.
On such supports the best way is to lead one main trunk direct to the peak and each winter cut back the canes along this trunk to short stubs (called spurs) of only two joints. The shoots developed from these spur buds will require tying where their foliage is needed to supply shade for the interior.
When trained against walls the vines should be on trellises, not fastened directly to the walls. The trellises should be such that they may be lifted free of the walls and laid on the ground when the walls need painting, which is best done during the dormant season.
The European varieties grown on the Pacific Coast are of much more stocky growth than the native American kinds and their hybrids. They are, therefore, more often cut back to stubs or spurs than trained with long arms. For this reason they are better adapted than American varieties to walls and other restricted spaces.
After having tried various styles of trellises and training I have discarded wood because it is short-lived and the framework loaded with vines is too likely to be blown down by wind or to break when loaded with fruit.
Perhaps the Kniffin (Fig. 49) is the most popular system of training used in the eastern half of the United States and for American varieties. In its modifications it meets economic considerations and differs from the Munson method mainly in having its two wires one above the other instead of at the ends of cross-arms. The principles of pruning are the same.
As in ordinary farm fencing heavy end posts of rot-resisting wood, such as locust, cedar or white oak, 8′ long or somewhat longer are set well below the local frost line, thoroughly braced and tamped to withstand the strain of wind and fruit. The intermediate, lighter posts should be 7 1/2′ long and set similarly but not braced. Usually they are spaced 30′ apart with two vines. planted each 5′ from the posts and one midway.
Number 10 or 11 galvanized wires are generally used, the former preferred because heavier and therefore more durable. The upper one is placed near the tops of the posts; the lower 2′ below. Both are securely fastened to one of the end posts but not tightly to any of the others, the staples being merely to keep them in position, not to prevent the slight movement necessarily due to expansion and contraction due to temperature changes. If too tightly fastened the posts will be pulled out of place. At the loose end enough wire should be left to allow for this movement and a device provided to take up the slack during warm weather. Various types are sold by garden supply stores and nurseries that specialize in grapevines.
One form of the Kniffin system requires two upright main trunks which start at or near the ground, one reaching to the lower, the other to the upper wire. Another form uses only one trunk but has a pair of branches (“arms”) extending in opposite directions on each wire. There is little if any difference in yield.
In the first case two strong shoots (instead of the one described under the Munson system) are developed from the newly planted vine during the first season if possible. As they grow they must be tied loosely to stakes in order to make straight trunks. Preferably when one reaches the height of the lower wire its tip is pinched and the other is similarly treated when it reaches the upper wire.
Generally it is more convenient to erect the trellis during the second spring or the first fall after planting and to use only 6′ or 7′ stakes the first year. Usually pinching encourages the development of branches of which the uppermost two on each trunk should be trained in opposite directions on the wires. All other shoots should be removed, preferably by pinching just beyond the first leaf.
When branch development does not occur the first season it will start in the spring of the second. Then development of the pairs and the treatment just mentioned will be necessary. In the former case several fruit-bearing shoots may be expected from one or more of the arms; in the latter the shoots may bear fruit but not be branched at the lower joints.
The style of training I prefer is the Munson or canopy system. (Fig. 50.) With it: 1. The work of pruning, spraying, tying and harvesting is breast-high or higher, thus preventing backache. 2. Currants, gooseberries, black raspberries or other low growing plants that do best in partial shade may be planted alternately in the same rows with the vines, thus saving space. 3. It is easy to pass from row to row beneath the vines instead of having to go around the ends. 4. It affords excellent distribution of heat, light and air to foliage and fruit. 5. There is less resistance to wind than when the vines are trained on a vertical plane and hence less likelihood of their being blown down. 6. The fruit is well shielded from the sun by foliage. 7. The trellises are easy to make and, 8, their cost is low.
To make the Munson trellis, use posts 5″ or larger at the top for the ends, long enough to be below the local frost line and 5′ or 6′ above ground. Line posts should be lighter but as long and as deeply buried as the ends. They are placed far enough apart to place three vines between; i.e., 30′ for vines to be planted 10′ apart, the usual distance for strong growing vines. The vines nearest the posts are placed half their distance from the posts—5′ in the above case.
Across the top of each end post is nailed a crosspiece of 2″ x 4″ scantling 2′ long and on the tops of the line posts 1″ x 4″ pieces. Previous to nailing, a notch 1/2″ deep is cut 1″ from each end and on one side. When nailing the crosspieces on the posts these notches are turned upward for the upper trellis wires to rest in them without stapling. The lowest wire is stapled 6″ below the top not too tightly to all the posts except one of the end posts. The crosspieces need not be put up until the spring of the third year as the vines will not reach them until then.
After the posts have been placed, run a number 11 galvanized wire (copper is better but more costly) from end to end 6″ below the tops of the posts, fasten securely at one end and provide a tightening device at the other.
The vines having grown one season on poles are pruned in winter to only one cane. If this reaches above the wire (after the wire is in place) cut only the excess and tie the cane to the wire. If not long enough to reach the wire, cut it back a half to two-thirds; if very weak, cut to only two or three joints, each with a strong bud. In the last case treat the new shoots as during the first year.
Kniffin and Munson winter pruning are the same—a renewal system. Each winter the two year old and older wood (except the trunks) is cut and replaced by ripened canes of the previous season’s growth. Each system makes necessary only one cut of each arm near the head of the trunk. Before cutting, however, the renewal arms must be chosen and freed from attachment to the other canes so that when the cut arms are pulled off the trellis these renewal arms shall not be broken or otherwise injured. These new arms should start as near the trunk as possible. Often as the vines grow older it may be necessary to get rid of accumulated wood where the arms have started. In such cases a cane may be cut back to one or two joints. From the buds on this spur new shoots will develop. The best one of these should be chosen to become the new arm in the following spring. The other must be cut off.
Whatever system of training chosen the shoots may be tied to bean poles during the first season. The second year the posts and wires of the trellis should be put in place. Or, better, they may be erected in the fall of the first year when work is usually slack. In commercial vineyards the vines are usually allowed to sprawl upon the ground during the first season, but they cannot thus receive the attention they deserve and as a result bearing seldom starts before the third year.
Shoots that develop the first year from the lower buds on the main cane (now called a trunk) often bear one to three clusters of grapes. Commercial growers recommend cutting off these shoots to strengthen the vine but I have never noticed the slightest weakening of any vine on which I have allowed them to mature. For I believe that a vine ambitious to set fruit knows more about its resources than any human does; so why should I interfere with its plans, especially when these lead to a gift of choice fruit!
Summer pruning, though formerly advised, has proved inadvisable, so don’t do any.
During the winter of the second year the Kniffin trellis must be completed by stretching the upper wire from end to end. To complete the Munson trellis two wires are similarly stretched in the notches on the crosspieces, fastened at one end and provided with a tightener at the other. Then every stub and cane except the ones wanted for arms must be cut close to the trunk and the arms shortened to eight or ten buds. The shoots that spring from these buds should yield two to four or even five clusters, so it is easy to calculate at pruning time how much fruit to count on the following fall. As the shoots develop they are allowed to form a “canopy” in the Munson system.
In the winter of the third and subsequent years the arms attached to the lowest wire and all inferior canes are cut off and only the strong renewal canes left. These selected canes must be carefully shortened as already described and fastened to the wires.
There are two insect pests and two fungus diseases that must be controlled to secure profitable crops. The rose chafer is a beetle about a third of an inch in length, yellow-brown in color, with long, ungainly legs. Almost overnight it comes in great numbers at the time when the vines are blossoming. It feeds on both the blossoms and the foliage. The grape berry moth is found almost everywhere grapes are grown. It lays its eggs on the growing grapes and the newly-hatched worms web the grapes together even as they feed on the green fruit. In July, a new generation comes along and when the eggs hatch, the worms feed on the grapes and puncture holes in the fruit. Both insects can be easily controlled by a spray. Use 6 pounds of arsenate of lead to 100 gallons of water.
The two fungus diseases are black rot and downey mildew. The first causes greater damage than any other disease in most localities. It can be easily distinguished by the many reddish-black specks which cause the fruit to become hard, black, and shriveled. The fungus disease, downey mildew, causes the leaves to curl up and drop off; it infects the fruit clusters, turning the grapes a grayish-blue color, and great quantities of the fruit fall to the ground. Fortunately the disease can be effectively controlled with Bordeaux mixture. It is wise for each farmer to write his state college and get the bulletin on control of grape pests and diseases.
In the past, a majority of farmers have used liquid sprays. There have now been developed many dusts and dusting machines. Many farmers find that dusting is as efficient as liquid spraying, and much easier. If one is using dust, either from a hand sprayer in the home garden or from a power machine, the directions that come with the dusting materials should be followed. In most instances, it is most efficient to use dusts early in the morning when the foliage is moist. The moisture helps the dust adhere to the leaves and fruit.