for a vertical trellis
- Line posts are spaced too far apart. Kuhn advises spacing line posts 32 to 35 feet apart for optimum performance; 40 feet is average, and 50 feet apart is asking for trouble.
- Line posts are too small, resulting in posts tipping over. Kuhn recommends using 3- to 4-inch-diameter posts, not less than 3 inches.
- Line posts are too short. Posts used to be 12 feet tall, sunk in the ground 2 feet, but are now recommended to be 14 feet, and to be put into the ground 3 feet deep. Posts that are too short don’t allow enough room for the proper number of support wires.
- End assemblies are built too small, anchored too shallow, or positioned at the wrong angle. He often sees anchors angled away from the orchard, and as the wires are tightened, the anchor moves toward the wood end post and becomes loose. Once the anchor loosens, the entire system is weakened.
- Too few wires are used for the fruit load. Old-style trellises used three wires; five to six are now needed to tie branches and support the increased tree and fruit weight in a vertical system.
for a V-trellis
- Spacings of the Vs are too far apart within the row to give adequate support.
- Wires are not clipped to the posts, and the trellis walks, which results in twisting.
- Horizontal supports to the Vs or between the Vs have not been added to hold the canopy together and keep trellis wires tight. (Once wires begin to bow, the system weakens and fails.)
- End assemblies are too small, causing anchors to pull out. Kuhn recommends using 5- to 6-inch-diameter end posts and a minimum of 3/16-inch cable (1/4-inch or 5/8-inch cable is even better) to secure end posts to anchors. Cable is easier to work with and significantly stronger than wire.
- Cross pieces added to the V supports are bolted instead of welded. Materials that are bolted have potential for loosening and movement, whereas good welds are permanent.
Although there are many types of mistakes that can be made when installing a trellis, the bottom line is to go bigger and stronger with today’s trellises.