Question: Where do I put the wires on my trellis, and how do I train the vines to them?
Answer: Grapes have traditionally been grown by the cordon system, with two wires running between posts, one at 42 inches and the other at 72 inches. Plant your vines against the stakes, and spend the first two years developing their scaffold branching. Tie the vines to the stakes. When each vine reaches 42 inches in height, pinch out its growing tip to encourage side branching. Remove all the side branches that develop, with the exception of the two that you select to be the main scaffold branches along the 42-inch-high wire. Using plastic plant ties, secure those lateral shoots to the wire and allow them to grow horizontally. After the first growing season, prune each of the lateral branches back to 4 feet in length from the main trunk. The second year you’ll want to allow the buds along each of those 4-foot lateral branches to develop upward shoots that will grow toward the 72-inch-high wire. When they reach the higher wire, attach them to it with the plastic plant ties. Remove all fruit that forms that second year. That will establish the basic configuration of your cordon grape planting.