Under natural conditions the wild vine climbs to the top of forest-trees and spreads out laterally in the tops, where it bears fruit exposed to the sun and air. While the vine is climbing upward it rarely if ever shows fruit until a branch assumes an approach to the horizontal position. Under cultivation practically the same plan is followed except in the way of shortening the stem and controlling the amount of fruit produced by cutting back the new growth, which alone produces the flowers and fruit. In Nature, the tree or rocks to which it clings gives stability and relative freedom from damage from winds, while under culture this is given in California by adopting the dwarf-tree form and in other sections by training on stakes or a wire trellis. Many plans of training on wire trellis have been practised in this country and Europe, but in this connection only those generally practised in this country will be considered.
In the North, especially in the prairie States, vines are pruned late in autumn and the canes laid down for winter covering. To avoid much bending in laying down, the main cane is trained on the lower wire, as in Fig. 68.
The first year it is usual to allow the vines to grow on the ground without care. They are not much in the way in cultivation, and they make about as much root growth and ripen their wood quite as well as when tied up. In the fall the growth is cut back to a stub which is covered with a mound of earth, and in the far North a covering of coarse manure is applied over the mound, as young vines are liable to be root-killed the first season after setting out.
The next spring the trellis should be made. For this system four wires are used, the lower one eighteen inches from the ground and the others about ten inches apart.
Fig. 68. - Completed vine. The lines at base show where to prune.
No. 12 galvanized wire is usually selected. The supporting posts are set from twelve to fourteen feet apart, with the end posts well braced to prevent being drawn inward, when the vines are loaded with foliage and fruit.
The second spring after building the trellis, carefully uncover the stubs and permit only one bud to grow, rubbing off the others as they start. Train the vine perpendicularly, and when it reaches the top wire pinch off the terminal point to develop laterals and growth below. In the fall cut off the laterals or side branches close to the main cane and cut the main cane back to well-ripened wood. In laying the cane down for covering, some earth is removed from the crown, as an aid to the careful bending of the cane, as low down as possible.
The third season, about the time the buds begin to start, take up the cane and tie to the lower wire, as shown in Fig. 69.
Fig. 69. - Vine in spring of third season.
During the third summer laterals are started upward, as shown in Fig. 70, which is effected by some pinching of surplus shoots. When the laterals reach the top wire they are pinched back. This pinching of the terminals favors the formation of fruit-buds near the main cane. In the fall of the third year cut back the upright shoots, as shown by the dotted lines in Fig. 70. The terminal cane is not dotted for cutting, as it is left entire for the extension of the cane on the lower wire, as shown in Fig. 71, when tied up the fourth spring. Usually with this system the vines give some fruit the third season.
The fourth spring shoots spring up from the spurs, shown in Fig. 71, and are pinched at the top wire and the main laterals are pinched to give shorter and firmer growth. In the fall the canes are again cut back at the dotted lines in Fig. 72, leaving from three to six buds, depending on the perfection of the canes.
Fig. 70. - Vine fall of third year. Dotted line shows where to cut in fall pruning.
Fig. 71. - Vine in spring of fourth year.
The fifth season the vine is completed at the close of the season, as shown in Fig. 68. The gain in this system is in the ease of laying down for winter protection and the even distribution of the bearing wood. In the prairie States it is also a gain to keep the fruit near the ground, with a leaf canopy above, but a circulation of air beneath. But the permanent success of the plan depends on summer pinching of the up-growing shoots and laterals. This summer pinching, if started early, develops fruit-buds low down on the laterals. If not pinched, the buds will
Fig. 72. - Vine in autumn of fourth year.
Dotted lines show where to prune. develop higher up, requiring longer spurs. We have kept a vine on this plan for twelve years without undue increase in length of spurs. If any of them get too long a new shoot can usually be started upward from the lower part of the spur.