Grapes need to be trained onto a trellis in order to spread the vine and provide light to the leaves and fruit clusters. There are different training methods for grapes.
For spur-pruned varieties, a bilateral cordon method works well. For cane-pruned varieties, a head-trained method is suitable.
The difference in pruning techniques is due to variability in fruitfulness. Cane-pruned varieties bear fruit further out on the cane, on buds numbered 4 to 12. Examples of cane-pruned varieties are 'Thompson Seedless' and 'Concord'. Spur-pruned varieties are much more fruitful and by being pruned back to a two-bud spur the vine is prevented from overcropping. For spur-pruned varieties such as 'Flame Seedless', 'Ribier', or 'Tokay', one would typically leave between 12 and 14 spur positions, depending on vine vigor. For cane varieties, leave between four and eight canes, again depending upon vigor. The more vigorous the vine, the more spurs or canes you can leave.
