The California county with the highest percentage of organic vineyards is Mendocino County.
Answer: True.
Mendocino has the highest percentage of organic vineyards of any county in California. According to the Wine Institute, the Mendocino AVA has about 16,700 acres under vine. Of that, almost 30 percent are certified by the California Certified Organic Farmers, with countless other vineyards being organic but not officially certified.