The best size and type of grapevine trellis depends on the variety of grape produced. More vigorous grapevines require more space, while the growing habits of others need multiple wires and careful training. Whether simple or complex, grape trellises must be sturdy. The weight of a good harvest will break down a poorly constructed trellis, and the long lifetime of grapes means that a permanent structure must last 20 years or more.
Single Wire Trellis
The simplest and least expensive trellis, the single wire trellis meets the needs of many home and commercial grape growers. One strong wire supported by a row of vertical posts forms the main framework. At the end of each row strong anchors prevent the trellis from sagging or collapsing under load. Height varies from 5 feet for wine or table grapes to 6 feet for muscadines.
Multiple Wire Vertical
Two-wire vertical trellises allow more options for training vines. Adding a lower wire to the single wire system allows two sets of cordons or fruit-bearing branches to grow from the main trunk, increasing yields. Adding even more supporting strands accommodates the upright growing habits of some varieties, and allows growers to use elaborate training methods which increase yields.
T-shaped posts support the three wires of a T trellis. One wire running down the center of the row supports the trunk of the vine and the main cordons growing to either side. The two wires at each end of the T's crossbar support fruiting canes growing from the cordons. Annual pruning cuts out older and less vigorous canes, making room for new growth and stimulating higher yields.
The Y trellis uses the arms of Y-shaped posts to brace as many as nine support wires. This elaborate trellis allows vigorous vines like sauvignon blanc to grow to maximum size. Harvesting and pruning difficulty increases with the Y system, and the high tension load of nine tightly pulled strands requires an unusually strong anchoring structure.
The 10-wire gable trellis resembles the peak of a house roof with five high tension wires running parallel along each side of the row. Two posts and rafters replace the single posts of other trellises and increase the initial cost. The gable trellis reduces shading but requires hand harvesting. According to the University of California, the combined pull of the 10 support wires creates 2500 lbs. of stress at the row's anchor points. Anchor posts 9 feet long--driven 5 feet into the ground--support the load.
Sloping Arm Trellis
Developed in South Africa, the sloping arm trellis uses a row of 3-foot vertical posts with 9-foot crossbars attached at a 35-degree angle. From seven to nine parallel high tension wires support the grapevine canopy, giving the plants excellent growing room and better exposure to the sun.