Growing Grapes in Your Backyard
See more detail in the pdf of Figure 15.8, linked below.
Grapes can be pruned in the winter after the leaves have fallen and the plants are dormant. However, it may best to wait to prune until early spring when growth just begins so that new growth, which will be delayed, will avoid damage from late-spring frosts. If first-season growth was weak, prune the trunk back to two buds (a two-bud spur) and replace the vine protection (milk carton, etc.) if used. Place a 6-foot (1.8-m) stake for training the vine if you did not do so at planting. If first-season growth was fairly vigorous, the single shoot can be tied to the stake or trellis without heading it back (see Figure 15.8A, linked below).
How do I . . .
Several examples of early training of vines with different vigor, using cordon training, Figure 15.8 (pdf) in California Master Gardener Handbook. UC. Buy Publication