Grapes can be grown to conform to numerous shapes: arbors, fences, and decorative trellises are only a few of the possibilities. The grower's imagination is the only limit to how the vines can be trained. Since many home gardeners opt to use a less traditional training system, they should remember the following pruning and training principles:
- The structure to which you are training the grapevine should be reasonably filled but not overgrown. This is easier said than done because even though the vine initially grows fairly slowly, as it matures it can become a monster of vegetation. One to two layers of leaves for any area on the canopy are best for flower bud and fruit development.
- Mature grapevines, by their very nature, produce much more wood than they can support. Think of the wild grapevine growing in the woods--it produces a huge amount of wood just to climb to the sunlight. Your grapevines won't need to do that since you're cultivating them, but, nevertheless, they will produce much more wood than is necessary or desirable. Typically, 90 percent of the new growth of a mature grapevine is removed during dormant pruning. Plan on leaving about three to four buds per foot of cordon (the horizontal trunk on a grapevine).
- Grapes bear their fruit on one-year-old wood. Figure 6.2 shows the cane that is formed from a single bud on a one-year-old cane.
- Different grape varieties have different growth habits. American grape canes tend to grow in a willowy, downward direction, while those of European and many French-American hybrid grapes tend to grow directly up. Choose your training system with this in mind.
By way of guidance, some of the traditional training systems employed by commercial and backyard viticulturists (grape growers) are described below. All figures shown depict a vine in the early spring after dormant pruning, which is usually done in February or March in Pennsylvania.