The trellis for the three methods carries two wires, the lower placed at the height of three to three and a half feet and the upper from two to two and a half feet above it. To permit this height of wires, the posts must be from eight to eight and a half feet in length, and must be firmly set with the end posts well braced.
Single-stem, Four-cane Kniffin.
As practiced at the New York Agricultural Experiment Station, the vines are trained as follows:
Fig. 18. Single-stem, Four-cane Kniffin training.
One trunk is carried to the top wire the third year after planting, or if the growth is not long enough at this time, it is carried to the lower wire and there tied. In this case, the following year a cane is extended to the top wire. This trunk is permanent. If the stem reaches the upper wire the third year, growers break out many of the developing shoots and allow only the strongest to grow, choosing those that arise close to the wires. The stem should be tied tightly to the top wire and somewhat loosely to the lower. If girdling results at the top, it is not objectionable as the head of the vine should be below rather than above the wire. When the shoots are sufficiently hardened, those growing close to the wires should be loosely tied to prevent injury during cultivation. At the beginning of the fourth year, as shown in [Fig. 18], the vine should consist of a stem extending from the ground to a point below the top wire. From this, all but two canes and two spurs of two buds each have been cut away below each wire level. As growth is most vigorous at the top of the stem, four to six more buds are left on the upper than on the lower canes. A vine of which the stem reaches the upper wire the third year should support the next season canes, aggregating twenty-two buds with eight additional buds on the spurs. If the growth is weak, only half this number should be left.
The tying at this time consists of fastening the stem loosely, with ordinary grape twine, to the lower wire, and with the same material the canes are tied along the two wires to right and left of the stem. The canes should be tied tightly toward the trunk so that they cannot slip out of the twine. Ordinarily tying at this time is sufficient for the year, but if conditions for growth are unfavorable, the twine may rot before the tendrils take hold of the wires, and a partial second tying may be necessary.
After the fourth season, the pruner has greater choice of fruiting-wood for the following year. It may be chosen from the basal canes of the preceding year's wood or the canes that develop from the spurs may be used. The choice should depend on the accessibility and maturity of the wood. At each pruning, the possibilities for obtaining fruiting wood for the following year must receive consideration. It is possible to use the same spurs for two or three years, but after this they should be cut away and new ones retained. After the first spurring, spurs should be selected from wood older than two years. The shoots from such wood bear but little fruit and hence make good fruiting canes for the next year.