Good Fruit Grower / February-1st 2013 / Rethinking ­trellis materials

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Rethinking ­trellis materials

Today’s high-density trellises are supporting 100 bins or more per acre.

The needs of today’s trellis systems are not what they were a decade ago. More apple orchards are being planted to high density, and yields have dramatically increased, requiring trellises to be stronger and more supportive.

Trellis systems must support weight today that would have been unimaginable ten years ago. In the past, yields of 40 to 60 bins per acre were the target to achieve. Now­adays, yields are way beyond 50—yields of 100 bins per acre are no longer unthinkable but becoming more common in high-density orchards. Instead of needing to support 40,000 to 60,000 pounds per acre, some trellises are supporting more than 80,000 pounds.

Steve Kuhn, of Wilson Orchard and Vineyard Supply, says he’s heard of yields reaching 105 bins per acre. “That works out to be over 600 pounds of weight per post in your trellis, assuming you are using a V,” he said. Wilson Orchard and Vineyard Supply, headquartered in Yakima, Washington, sells irrigation and other products, including trellis supplies. Wilson does not install trellises, but provides growers with trellis materials.

“We generally get called in on the failures and invited to fix things when something goes wrong with the trellis,” Kuhn said. When a trellis collapses or weakens, a grower has to add more trellis materials to strengthen the system or go in with a whole new plan, he said.

“Growers have learned by trial and error, and we’ve all learned from the mistakes made by others,” Kuhn said, adding that his recommendations are based on collective knowledge of the industry.

He noted that last fall, a Fuji orchard in central Washington had such a heavy yield that the trellis collapsed, with branches, wires, and posts down. “That’s what you want to avoid,” Kuhn said.

Trellis basics

As orchards have changed in appearance in tree structure with closer spacings (14-foot rows are now 10 feet) and higher yields, growers must recalibrate their thinking when it comes to trellis materials. Today’s trellis systems require heavier materials and end posts, putting line posts closer together, and using more wire in comparison to trellises of the past.

Also, more clipping options exist than in the past. Clips should hold the trees and branches in place, while still allowing some movement and without causing girdling. Kuhn said using tape to tie branches to wires is not as popular as it once was.

Staples to keep wires attached to line posts should be placed in the center of the wood and driven at an angle so the tips spread to ensure barbs are secured in the wood.

Wrapping wire around the end posts used to be a common way to tie-off wire, he said, but posts can be cut in two by the wrapped wire. He suggests growers use a piece of steel between the post and wires to prevent wires from cutting into the post.

Labor needed to install the trellis is also a consideration. Kuhn estimated that installing the trellis is frequently as expensive as the cost of materials. Growers should take advantage of devices, supplies, and techniques that save labor by being easier to work with or reduce labor during installation. He noted that a new tightening system is available that allows one worker instead of three to tighten or pull wires.

In an effort to reduce installation costs, he said a few Washington growers are experimenting with using steel tubing for support in their V-trellis, keeping the height down and reducing labor costs.