Why thousands of sheep visit these organic California vineyards every winter

About 3,000 sheep graze on the vineyards at Bonterra, helping encourage biodiversity in the soil.

When winemaker Bob Blue started working at Bonterra Vineyards 30 years ago, organic farming and winemaking were considered a little out-there. Now the terms composting, cover crops, biodiversity and soil health are much more understood.

"People would look askance at us," he says. "Now, organic is more prevalent, and it's carrying over into wine as well."

The California winery planted their first organic vineyards in 1987 in Mendocino County. Now Bonterra owns 11 ranches, three of which are certified biodynamic by the Demeter Association, and all are certified organic by California Certified Organic Farmers.

It starts in the vineyard

But what does organic farming mean? There is a long list of substances, both synthetic and non-synthetic, that are prohibited in organic farming in regards to pest and weed management and fertilization. But farming methods are also important, partnering with the environment and "getting nature to work for you," Blue says, be it with other plants or even animals like bees, chicken and sheep.

"Everything starts in the vineyard. All kinds of things happen there," Blue says. Some of the most important practices they use are composting and cover crops.

Cover crops

Biodiversity means growing more than just grapes. Bonterra's vineyards grow more than 100 species of plants in addition to grapevines. There are olives, apples, apricots, plums and more on the property. Other plants, such as clovers, Austrian winter peas, daikon radish and more grow in between the vineyard rows as cover crops, which are used for the protection and enrichment of the soil.

"There used to be a time when the perfect vineyard looked barren, with just vines growing, but now you see cover crops," Blue says.

Cover crops get tilled under and into the soil, decaying and adding more nutrients.

"It's really exciting for us now, the acceptance [of organic]," Blue says. "Many of these techniques are considered a standard practice now, whether organic or conventional. It's just considered good practice."

Biodynamic farm standards take things a bit further. The standards are kind of like organic-plus, and emphasize that each farm be a closed ecosystem, bringing in as few materials as possible. There are also standardized soil preparations that include animal manure, minerals and herbs.

CCOF certified 12,650 acres of wine grapes for 2017 in California. It's still a small percentage of the state's nearly 600,000 wine grape-growing acres, but the number is steadily increasing. CCOF has seen a 13 percent increase in the number of acres of organic vineyards in the state since 2013.

Natural partners

Insects and animals are another big part of organic farming: They eat pests, trim weeds, and build soil health.

Bonterra often releases chickens in the vineyards as well as a few thousand sheep from a neighboring farm. In the winter, before the grapes have budded out, the sheep are let loose on the property, eating several inches of cover crop and "recycling" it back into the soil as a natural fertilizer. "It saves us three passes through the vineyard to mow and till the crops. It saves all that fuel," Blue says.

This technique is a form of mob or strip grazing — according to the U.S. Department of Agriculture — which helps the soil by minimizing tilling and maximizing organic matter.

"It's like the soil is drinking probiotics. It's the same principle," Blue says.