Mendocino AVA

Viticulture has been active in the Mendocino region since the earliest settlement in the mid-1800's. According to the Mendocino County Assessor's records, 25,000 grapevines, or about {{cvt|40|acre|sqmi|2}} had been planted by 1871. By 1910, grapes and wines from the area were listed as principal products of the county. At that time, there were {{cvt|5800|acre|sqmi|0}} of grapes and nine wineries that produced {{cvt|90000|usgal|l|0}} of wine in the Mendocino County. The most popular grape variety of the time was Zinfandel, and today it is still one of the major grape varieties grown in the area. In the early 1970's, large acreages of new vineyards were established within the area, and consequently, the number of wineries increased.

The Mendocino viticultural area encompasses cultivated agricultural areas in the southernmost one-third of Mendocino County. The Mendocino area is shaped like the letter “V” with two forks. It includes the watershed areas and drainage basins of both the Navarro and Russian Rivers. The eastern fork encompasses the Russian River watershed, starts at the headwaters of the Russian River and extends approximately {{convert|30|mi|km|0}} south. At its widest point on the north end, the viticultural area is about {{convert|12|mi|km|0}} wide, encompassing Redwood and Potter Valley with a hilly outcropping separating them. Its narrowest point just south of the middle is {{convert|6|mi|km|0|spell=in}} wide. The east fork is approximately {{convert|30|mi|km|0}} inland from the Pacific Ocean and runs almost parallel to the coastline. The west fork of the viticultural area, consisting of agricultural areas found in both the Navarro and Russian River watersheds, starts approximately {{convert|1|mi|km|0|spell=in}} south of a fork in the Navarro River

and extends southeast approximately {{convert|34|mi|km|0}}. At its widest point on the north end it is approximately {{convert|8|mi|km|0|spell=in}} wide and in the middle at its narrowest point, it is {{convert|4|mi|km|0|spell=in}} wide. The west fork also runs parallel to the Pacific coastline, approximately {{convert|15|mi|km|0|}} inland. At its south end the west fork bends sharply to the east, joining the east fork at its southwestern boundary.

The majority of AVA's vineyards are at elevations ranging from {{convert|250|to(-)|1100|ft|m|0}}, with some at {{convert|1600|ft|m|0}} on the hillsides in the area. The surrounding mountain ridges define the Upper Russian River and Navarro River drainage basins. These ridges, rising as high as {{convert|3500|ft|m|0}}, are the natural boundaries of area climates referenced in the petition for the Mendocino viticultural area.

The Mendocino viticultural area is distinguished from surrounding areas by climate generally separating the coastal and interior climate areas and has a very unusual climate pattern. It lies in a climate area called "Transitional." The area is unusual in climate because either the coastal or the interior climates can dominate the Mendocino climate for either short or long periods of time. Generally this is reflected by a warmer winter and a cooler summer than the interior climate area east of the viticultural area. Also, it provides a grape growing season that has many warm, dry days, and generally cool nights.

The north end of the west fork of the Mendocino area, near Philo has a very unique microclimate. This area is cooler than the rest of the viticultural area and is classified as Region I on the University of California heat summation scale developed by Amerine and Winkler. All references to heat summation and distribution of heat, mentioned throughout this document, were gathered from climate studies made by the University of California Agricultural Extension Service offices located at Lake, Mendocino and Sonoma Counties. The Boonville area, which is located southeast of Philo, is warmer and is therefore classified as Region II. The overall climate of the Anderson Valley area is described as "Coastal" by the Mendocino County Farm Advisor's Office, in their booklet, "The Climate of Mendocino County." The total average heat summation for Mendocino AVA for the period of April through October is 3,097 cumulative degree-days and is therefore classified as Region III.

The Mendocino area has a rainy season of moderate temperatures and a dry season with high temperatures. The rainy season occurs in the winter months from October through April and the rainfall in this area is greater than the state’s Central Valley area. The five months from May through September constitute the summer or dry season. The average annual temperature for the area is about {{cvt|59|F|C}} and the annual precipitation varies from about {{cvt|44|in|mm|0}} in the northern area of the western fork of the proposed area to about {{cvt|37|in|mm|0}} in the south.

Climatically, Mendocino falls somewhere in the middle between Sonoma County and Lake County. The average Mendocino growing season is 268 days and rainfall averages {{cvt|39.42|in|mm|2}} per year. The distribution of heat for June, July, and August averages 602 degree-days and falls between Lake County (678) and Sonoma County (541).

In comparison, Sonoma County, a major grape-growing region to the south of "Mendocino” displays a profound marine influence. This is apparent in the distribution of heat summation (cumulative degree-days) for the area. Winter is mild, resulting in an average growing season of 308 days with the marine influence providing a slightly warmer spring which promotes a bud break up to 10 days earlier than in the Mendocino area or in Lake County. The marine air influence in Sonoma County extends throughout the summer, holding cumulative degree-days for June, July and August to a lower average than either Mendocino or Lake County. The total average heat summation for Sonoma County for the period of April through October is 3,046 cumulative degree-days, placing it just at the lower range of Region III for grape growing as defined by the University of California. Average rainfall across Sonoma County is the lowest of the three areas being compared, with a range of from {{cvt|40.50|to(-)|24.10|in|mm|2}} and an average of from {{cvt|32.32|in|mm|2}}.

Lake County, east of Mendocino, represents a more harsh continental influence with some moderation occurring due to the location of Clear Lake. The average growing season in Lake County (223 days) is shorter than in Mendocino or Sonoma County. Also, cumulative degree-days for June, July and August are much higher in Lake County than in the other two areas. Average cumulative degree-days for Lake County for the months of June, July and August are 491, 771, and 771 degree-days, respectively. The average heat summation of cumulative. degree-days

for Lake County for the months of April through October is 3,380 and is therefore classified at the higher range of Region II. In addition, the beginning of the Lake County growing season is cooler than Sonoma County, with a more rapid drop (comparatively) to winter temperatures. Also, annual rainfall is more variable throughout Lake County, ranging from {{cvt|30.65|to(-)|62.16|in|mm|2}} with an average of {{cvt|45.21|in|mm|2}}.

{{reflist}}

• [https://www.mendowine.com/ Mendocino Winegrowers]
• [https://www.ttb.gov/AVA/ TTB AVA Map]

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Category:American Viticultural Areas of Mendocino County, California

Category:1984 establishments in California

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