A SPECIAL GROWERS’ REPORT OF AG ALERT ® CALIFORNIA Trees & Vines
High-wire trellises prep vineyards for hotter climate By Caitlin Fillmore A high-wire trellis system for winegrapes, at right, rises above a traditional vineyard alignment, at left. Researchers say high-wire systems provide better shade and more protection from heat and sun.
as they grow toward the top wire and later support the vines as they become heavy with fruit and foliage. Experts predict extreme heat days in Monterey County will triple in the next decade and stretch from May to November. As a result, despite being easier to harvest than HWC trellising, traditional vertical-shoot positioned trellises may be no match for sustained heat expected during critical periods of the growing season. “People are trying to search for new methods to avoid sunburn and heat damages in the coastal regions. The temperature has been going up, and the solar intensity has been going up with it,” said Cliff Yu, assistant professor of viticulture at California State University, Fresno. “Farmers can play with canopy management practices, but choosing the suitable and ‘future proof’ trellis system when planting might be a better and more permanent solution.” Researchers at the Department of Viticulture and Enology at the University of California, Davis, are studying benefits of HWC trellising. In their 2022 report published in the journal Frontiers of Plant Science, researchers concluded that the single high-wire trellis system provides more shade than VSP systems. In comparison, lower-hanging fruit in VSP trellises may be too vulnerable to overexposure, the study said. The HWC system works best in a hot climate with several consecutive days of triple- See TRELLISES, Page 11
Central Coast winegrape growers are moving away from traditional trellising systems as they seek to stay ahead of the changing climate in protecting vineyards from sun and heat impacts. Daryn Miller manages 3,500 acres across 10 separate vineyards throughout southern Monterey County as regional manager for Monterey Pacific, a vineyard management company in the Salinas Valley. He grows chardonnay and pinot noir winegrapes from Gonzales to south of Soledad and sauvignon blanc and cinsault in King City. Since 2022, Miller has encouraged high-wire cordon trellising, a technique he began learning in 2013 for the Loma del Rio vineyard redevelopment project near King City. He said a cordon height above 50 inches under the HWC system helps mitigate fruit dehydra- tion, limiting overexposure to the sun, with the vine canopy grown more as a sprawl rather than vertically positioned shoots. “I continued to make efforts to push for the utilization of high wire on new developments, due to my experiences with high wire being more adapted to late-summer heat events,” Miller said. Since the 1980s, coastal California vineyards typically used a vertical-shoot positioned trellising system, or VSP, with grapes hanging near waist height and shoots trained up- ward to provide a curtain of foliage. In the newer HWC system, the cordon—or fruiting stem of the vine—is raised up to 6 feet off the ground. Lower wires help train young vines
10 Ag Alert July 31, 2024
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