Jan 22, 2016

Replacing vineyard roses with native plants

As deficit irrigation and water conservation become increasingly important in Washington, researchers at WSU are exploring alternatives to the tradition of planting roses at ends of rows in vineyards.

Traditionally, vineyards across the world have relied on roses as more than just a beautification tool. Roses serve as an early warning system for pests and disease. The iconic ornamental plant shows signs of diseases like powdery mildew earlier than the grapevines, alerting growers that they should treat the vines for the disease.

With the development of forecast models, including WSU’s AgWeatherNet, which predicts when mildew and other diseases will appear in crops, roses are no longer used as an indicator for mildew on grapevines.

At the teaching vineyard at WSU’s Wine Science Center, which runs on a deficit irrigation system that requires little watering, traditional rose plantings don’t meet with water conservation standards.

“We wanted to find some alternatives that would allow for the continuation of the tradition of growing flowering plants at the end of the rows, while also supporting beneficial insects,” said Thomas Henick-Kling, director of the WSU Viticulture and Enology Program.

Henick-Kling, WSU Tri-Cities greenhouse manager Gretchen Graber, and entomologist David James wanted to feature native plants at the teaching vineyard and decided to use bitterbrush, rabbitbrush and purple sage.

Each plant blooms at different times during the year: bitterbrush from late April to early May, purple sage at the end of May, and rabbitbrush from late August to November.

“I purposefully chose three species with staggered bloom times to provide a constant source of food for the beneficial insects feeding on the nectar,” Garber said. “At the same time, those insects act as pest control.”

Graber said using native plants that are adapted to the soil type, climate and weather patterns in the area, helps to conserve native insects. Additionally, the practice reduces the need for pesticides. It also means that the wine created from the vineyard  can be marketed as a sustainably-grown, which adds economic value for producers.

“It takes one or two years of minimal watering to get the plants established,” she said. “Afterward, they need no additional water. That is a direct advantage for using native plants – they are adapted to live in the harsh conditions found in vineyards in arid habitats. Using native plants adds another layer of sustainability.”

Roses may never be phased out completely because growers still find uses for them stretch beyond their aesthetic value.

“A tiny wasp called anagrus is responsible for most of the biological control of grape leafhoppers.” James said. “The roses provide an overwintering habitat for anagrus.”

— Maegan Murray, Washington State University