The North Coast California is segmented into several over-arching AVAs that can be thought of as a very large GI zone. These AVAs encompass sweeping geographical and climatic similarities while also serving a commercial purpose in permitting appellation designations to appear on a label. The North Coast AVA includes the counties of Mendocino, Sonoma, Napa, Marin, San Francisco, Lake and Solano. It covers over 8,000 square kilometres and more than 50 AVAs, including Napa Valley and North America’s smallest AVA―Cole Ranch―a single-producer AVA that’s home to just 24 hectares of vines. Mendocino County Mendocino County sits directly north of Sonoma. It’s one of California’s most aesthetically striking areas, with dense forests cloaking low-lying mountains. The Mendocino AVA has stricter boundaries than the county itself and is located at the confluence of the Navarro and Russian Rivers. Established in 1984, the AVA covers 111,369 hectares of land and holds a number of sub-AVAs within its borders. Pinot Noir and Chardonnay thrive across the region with notable examples of traditional-method sparkling wine bottled by the likes of William Selyem and Littorai. Syrah, Zinfandel and Carignan find success in the warmer AVAs further inland. Cabernet Sauvignon has some commercial appeal here due to easier access to water compared to Napa or Sonoma. Anderson Valley A cool-climate region in Mendocino County, this AVA lies on the western slope of the Coastal Mountain range, 90 kilometres north of San Francisco and just 16 kilometres from the Pacific Ocean. The Anderson Valley AVA was established in 1983 and has just under 1000 hectares under vine. It’s 16 kilometres end to end and under two kilometres wide, but elevation ranges from 240 to 400 metres. The coastal edge―where most vineyards are located―is influenced by cool winds and fog from the coast. The valley is closely framed by steep hills, with only a couple of patches of land that might pass for valley floor; the vast majority of the vineyards are located on the south-facing slopes. Beyond the valley, the area is surrounded by forests of Douglas fir and California redwoods. The AVA is prone to wide temperature swings, with the average yearly temperature coming in at less than 15 degrees Celsius―cementing it as one of California's coolest wine regions. Louis Roederer bases its US operations in this AVA, likening the weather conditions to that of its home in Champagne. The Anderson Valley is well known for making premium sparkling and still wines using Pinot Noir and Chardonnay, as well as some aromatic whites like Riesling and Gewürztraminer. Sonoma Sonoma County is one of the largest of northern California’s coastal counties. Vineyards are everywhere, and it’s a geologically and climatically diverse area. To the east, the Mayacamas mountains mark the boundary between Sonoma and Napa, and the Pacific Ocean laps at its western edge. Some 80 kilometres of coastline are buffered by a ridge protecting vineyards nearest the coast from conditions too extreme to ripen grapes. The county contains 19 AVAs, ranging from warm regions where Cabernet Sauvignon and old-vine Zinfandel can reach 16% alcohol and above to cooler areas that can produce lean, racy Chardonnay. Sonoma and Napa counties enforce labelling laws requiring the county to be listed on the label, regardless of whether the label already states an AVA (e.g. Sonoma Coast). Unlike Mendocino or Napa, there is not an overarching AVA for Sonoma; however, all 25,000 hectares under vine are included in at least one of the county’s 19 AVAs. Sonoma Coast The Sonoma Coast AVA is a vast appellation that spans over 200,000 hectares of land, incorporating miles of rugged coastline and extending further inland than the Russian River Valley in some places. The coolest areas of the AVA can be found in the northern reaches near the coast, where altitude, exposure, high rainfall, cool sea air and fog combine to moderate temperatures and provide ideal conditions for Pinot Noir, Chardonnay and cooler-styled Rhône reds. Conditions further inland and towards the south are typically warmer and produce bolder-styled wines. Importantly, West Sonoma Coast AVA, which was approved in 2022 and accounts for about 20% of the vineyard plantings within the Sonoma Coast AVA, celebrates the uniquely cold, marginal and maritime growing conditions of this region, providing distinction to those vineyards which are truly coastal. The border of this AVA hugs the coastline and runs south from Mendocino. Fort-Ross Seaview This coastal AVA was recognised 11 years before the West Sonoma Coast AVA, and is now fully nested within it. Its westernmost vineyards do not reach the coast, as the West Sonoma Coast AVA includes all potential vineyard land up to the coastline. Pinot Noir is the headline act here. Petaluma Gap Petaluma Gap is just 40 kilometres from the Golden Gate Bridge and was designated an AVA in 2018. It takes its name from a gap in the Coastal Range that stretches from the Pacific Ocean to the town of Petaluma, granting cool winds and fogs inland access. Winters are cool and wet, and summers warm and dry, making this a cool area with a wide diurnal range and a long growing season. The AVA spans more than 80,000 hectares, of which only 1,600 or so are under vine. It is renowned for its Chardonnay, Pinot Noir and Syrah. Russian River Valley This sub-AVA lies at the heart of Sonoma County. The Russian River itself flows from Mendocino County south through Alexander Valley before cutting west at the town of Healdsburg and making its way towards the Pacific. Approximately 25 kilometres east to west and the same north to south, the AVA lies at the heart of this western kick, a sweet spot with ideal growing conditions. Established in 1983, and with 5,733 hectares currently under vine, the AVA is regarded for Pinot Noir and Chardonnay, but its varied climate also allows for the production of Zinfandel and Rhône varieties. The soils are fertile and alluvial, with plenty of the Goldridge sandy loams characteristic of the valley. Warm daytime temperatures are moderated by the river and fog from the Petaluma Gap to the south. The Russian River Valley growers association has drafted five unofficial sub-regions to better distinguish the diverse soils and climates: Santa Rosa Plains, Middle Reach, Laguna Ridge, Sebastopol Hills and Eastern Hills. The fully nested Green Valley AVA was established at the same time as the Russian River Valley AVA. Castelli Knight Ranch Vineyard: photo by Leigh-Ann Beverley Chalk Hill Chalk Hill is a small AVA at the bottom of Alexander Valley, mostly nested within the northwestern corner of the Russian River Valley. Merlot and Cabernet Sauvignon dominate. The soils here don’t contain chalk but are chalky white in colour, hence the name. Bennett Valley Recognised as an AVA in 2003, this is a gently sloping, elevated valley set between three mountains in Sonoma County. It’s a small AVA, spanning over 3200 hectares but with just over 260 of those under vine. The Valley enjoys a combination of rocky volcanic soils and cooling marine influences (fog and ocean winds), allowing for long, moderate growing seasons. Dry Creek Valley Dry Creek Valley is one of the northern AVAs in Sonoma County, enjoying a warmer climate than those like the Russian River Valley to the south. The area is 25 kilometres long and 3.5 kilometres wide and is home to just over 3,500 hectares of vines. Established as an AVA in 1983, it’s best known for producing ripe and powerful Zinfandel, although some excellent Cabernet and Syrahs have gained attention more recently. Alexander Valley Sandwiched between the Dry Creek and Knights Valleys, Alexander Valley is a warm, inland, northern AVA of Sonoma. Cabernet Sauvignon and Merlot predominate, and the area is home to some very old material (some Zinfandel and Carignan vineyards date back to the 1890s). Carneros Recognised in 1983, this AVA spans both Sonoma and Napa counties. The hills of Carneros are the first vineyards visible as you move north from San Francisco. The Napa side of the AVA is referred to as Los Carneros, while the Sonoma side is known simply as Carneros. It has the lowest rainfall in the Napa Valley, and the soils are predominately sandy loam over clay. The area comprises low rolling hills (elevations range from zero to 215 metres) north of San Pablo Bay and is heavily influenced by fog and cooling breezes. This results in conditions suitable for cool climate varieties like Pinot Noir and Chardonnay. Many sparkling wine producers are based here, for instance, Moët’s Domaine Carneros. Other Sonoma County Avas Some of these AVAs are recent additions formed to bring distinction to areas which have grown in importance over the years. Others were formed in the county’s first tranche of AVAs in 1983: Fountain Grove District; Moon Mountain; Northern Sonoma; Pine Mountain-Cloverdale Peak; Rockpile; Sonoma Mountain; and Sonoma Valley.