The heading-in of the main canes, while desirable for the purpose of keeping the vine within bounds, is apt to cause a growth of laterals which choke up the vine and which do not mature, and in those styles of training in which very little wood is allowed to grow, the practice may prevent the development of a sufficient amount of leaf surface to properly sustain the vine. Vines are often weakened by summer pruning. These dangers can be overcome by careful attention, however, especially by heading-in very lightly and by doing it as late in the season as possible, when new lateral growth does not start readily. The necessity of much heading-in has been largely obviated in late years by the adoption of high or drooping systems of training, and by setting the vines far apart. The strong varieties, like Concord, Brighton and Niagara, should be set ten feet apart in the row, especially if grown upon the Kniffin system. Catawba, being a very upright grower and especially well adapted to upright training, may be set eight feet apart, and Delawares are often set as close as six or eight feet. It is doubtful, however, if any variety should be set less than eight feet apart for trellis culture. In Virginia and southward, where the growth is large because of the long seasons, vines are often set more than ten feet apart. In the South, the rows should run north and south, that the fruit may be shaded from midday sun. The only summer heading-in now generally recommended is the clipping of the tips when they fall over and begin to touch the ground. This clipping is often done with a sickle or sharp corn-cutter.
_Objects of Pruning._--The objects of pruning the grape, as of other fruits, are five:
2. To maintain or augment the vigor of the vine.
3. To keep the vine within manageable limits.
PRELIMINARY PREPARATIONS FOR TRAINING--THE TRELLIS--TYING.
Training the grape vine is practiced for the purpose of keeping the vine in convenient shape and to allow each cluster to receive its full amount of space and light. A well trained vine is easily cultivated and sprayed, and the grapes are readily harvested, and it is only upon such vines that the best and fairest fruit is uniformly produced. Some kind of training is essential, for a vine will not often bear good fruit when it lies upon the ground. In essence, there are three general types or styles of training, which may be designated as the upright, drooping and horizontal, these terms designating the direction of the bearing shoots. The upright systems carry two or more canes or arms along a low horizontal wire, or sometimes obliquely across a trellis from below upwards, and the shoots are tied up as they grow to the wires above. The horizontal systems carry up a perpendicular cane or arm, or sometimes two or more, from which the shoots are carried out horizontally and are tied to perpendicular wires or posts. The drooping systems, represented in the Kniffin and post-training, carry the canes or arms upon a high horizontal wire or trellis and allow the shoots to hang without tying. To one or another of these types all the systems of American grape-training can be referred.