Staff Project Update

UC Davis Vineyards Use Cover Crops, Hedgerows
By Robert L. Bugg, SAREP

UC Davis vineyards are going under cover, but this does not imply that they are becoming less conspicuous. Since the fall of 1998, they have been planted with a range of different perennial and annual grasses, clovers and wildflowers to revitalize the vineyard understory.

Late spring: Mixture of non-native perennial grasses used as cover crop in UC Davis vineyards. (photo by Robert L. Bugg)

The addition of cover crops is due to vineyard manager Richard Hoenisch and his field staff, who have made changes to the sites in consultation with SAREP staff member Robert Bugg, Chuck Cambra of Kamprath Seeds in Manteca, and Scott Stewart of Stewart Conservaseed in Elk Grove.

Located along the Putah Creek Preserve west of the main campus, the UCD vineyards were ablaze with golden California poppy, blue lupines and phacelia, yellow tidy tips, pink Persian clover, scarlet crimson clover, and magenta redmaids during the spring of 2000. Currently, 52 of the total 140 acres are under some sort of cover-cropping regime; another eight acres are being added in the fall of 2000.

“Cover cropping is just part of our overall commitment to managing bio-responsibly,” Hoenisch says. Trained at UC Davis where he received a doctorate in plant pathology, Hoenisch previously managed private vineyards in Hopland and Paso Robles. The vineyards’ riparian zone supports many native plant and wildlife species, according to Hoenisch.

“Rather than relying on tillage and pre-emergence herbicides, we’re using cover crops and hedgerows to keep our soil from eroding and provide foraging habitat for Swainson’s, marsh, and red-tail hawks and other predators,” Hoenish says. He says the vineyards are on very deep, highly fertile soils, which sometimes results in excessive vigor for winegrape varietals.

“We’re using drip irrigation, close vine spacing, and cover to reduce vigor and enhance quality,” he says.

Grasses

Hoenisch notes that perennial grasses used as cover crops are very good at improving access, particularly during wet springs.

“The perennial sod-forming and bunch grasses are like walking on a carpet for the workers, a benefit often understated,” he says. “There is much less dust on the fruit in vineyards with perennial grass cover crops.”

Hoenisch says some growers and managers are hesitant to use cover crops because they are concerned with vineyard appearance.

“Cover crops look great most of the time, except during the late spring and early summer when they go to seed. But we like to accommodate the cover crop biology by delaying our mowing until seed is mature. This whole project has been done on a shoestring budget so far, and self-reseeding cover crops save us money,” he says.

Traps are used to combat gophers in the vineyards, according to Hoenisch. “The raptor population including the hawks, barn owls and blue herons help us out, too,” he says. The vineyard staff has constructed five owl boxes to attract owls, and the local riparian habitat encourages the raptors.

Hedgerow project

The UC Davis vineyards are hosting a research project on insectary hedgerow plants designed by Danielle LeGrand, a weed science graduate student in the Department of Vegetable Crops.

“Danielle’s project addresses our need to develop border plantings to harbor desirable wildlife,” Hoenisch says. “Naturally we are concerned about the arrival of the glassy-winged sharpshooter, and screening and continued monitoring of prospective landscape plants for host status are high priorities. But we don’t want to overreact by excluding non-crop vegetation altogether.”

In fall 2000 Hoenisch and staff are adding culinary and medicinal herbs to vine row ends and to vineyard entrances, many in the UC colors of blue and gold. The spectacular fields of California poppies and lupines that once dominated much of the state landscape are the inspiration for the official UC colors.

Plans for wetland

Hoenisch and Bugg are applying for grants to implement other aspects of Hoenisch’s plan, including establishing a mini-wetland planting around the drip irrigation sump, and the addition of raptor and bat nesting boxes.

“Cover cropping and most of these other options are well-established in the industry, but by no means universally understood or practiced,” Hoenisch says. “It’s hard to overestimate the educational value of having such techniques in place on UC lands. Students, faculty, tourists — everyone who uses or visits the vineyards — can see that the techniques work.”

Hoenisch and Bugg have given eight joint presentations to visiting groups of students and vineyardists through the fall of 2000.