Trellis enhances grape quality

Wine grape pioneer Dick Boushey continues to fine-tune his viticultural practices to improve grape quality. One example is his experimentation with a different trellis design for his red wine grapes.
He’s converted several rows of Syrah and Sangiovese from the VSP (vertical shoot position) trellis to the Geneva double curtain, a trellis system developed in New York in the 1960s for nonvinifera grapes. The Geneva double curtain was developed as a way to encourage higher yields while controlling canopy and was designed for juice grapes.

It’s used by Washington juice grape growers and wine grape growers in California who have very vigorous sites. The design is similar in concept to the V-trellis used in tree fruit.

Boushey’s idea in experimenting with the Geneva double curtain was not to increase yield but to spread out the fruiting zone and allow more room for clusters and improve sun and air exposure for the fruit.

“For Sangiovese, you need good color and good air movement,” he explained, adding that in Sangiovese, it’s important to prevent the clusters from touching each other. “I thought that with the Geneva double curtain I could space out the clusters better without compromising yield. In vertical shoot positioning, when you bring the two wires up to hold the canopy in a vertical position, it creates a very dense fruiting zone.”

The Geneva double curtain trellis worked so well for Sangiovese that he’s been trying it with Syrah, and had the same impressive results—more intense berry color, smaller clusters and berries, and just a little more yield.

His winery customers were apprehensive at first, he said. “But now everyone wants me to do their rows that way because the clusters and berries are smaller and color is intense.”

For the new trellis system, he divides the canopy horizontally by putting the bilateral cordons on alternating sides of the vine. Cross arms are used to support the cordon wires that to keep the sides (and canopy) about two feet from each other, creating a window that goes down the middle of the vine row. Short shoots hang over the cordon wires and create a canopy that has the appearance of two “curtains” on each side of the cross arm.

Boushey has moved the fruiting zone to about five feet off the ground, which makes hand harvest a little easier because there is less bending over. The trellis can be mechanically harvested if desired.

So far, sunburn hasn’t been a problem despite the more open canopy.

His conversion to the Geneva double curtain was done on an older planting spaced 9 feet between rows and 6 feet between vines. His newer plantings are spaced 7 by 4 feet. He plans to continue experimenting and expanding the new trellis in his Syrah plantings in an effort to improve fruit quality.