Petaluma Gap AVA Map

Windswept Petaluma Gap’s growers reach for wine imprimatur

Posted on Aug 30, 2017

The former egg capital of the world is poised to gain official recognition as a premium wine region.

The Petaluma Gap is on track to be named California’s newest American Viticultural Area. A public comment period ended Dec. 27, with no opposition. Now it’s up to the Alcohol and Tobacco Tax and Trade Bureau to issue final approval, expected in the next few months.

Stretching over 203,000 acres of Sonoma and Marin counties, the Petaluma Gap AVA would extend from the coast at the northern tip of Tomales Bay to Sonoma Mountain. It would be the 17th sub-AVA within Sonoma County — and to the petition drafters’ knowledge, the only AVA in California defined by its wind patterns.

“The wind is our constant,” said Rickey Trombetta Stancliff, president of the Petaluma Gap Winegrowers Alliance and owner of Trombetta Family Wines.

Passage of the AVA would be a huge boon to Stancliff and the other vintners who make wines from the Petaluma Gap. An AVA brings marketing possibilities, codifying the area’s distinctiveness for consumers. One vintner’s success becomes the AVA’s. Not to mention that AVA-designated wines usually command higher prices.

An AVA, in basic terms, is a government-designated geographic boundary for grape- growing. Essentially, it’s a labeling issue. If you grow your grapes within the official borders of the Napa Valley AVA, for example, you can label the resulting wine “Napa Valley.” 

That process owes much to the appellation systems of Old World winegrowing countries like France and Italy. But unlike the French AOC system or the Italian DOCG system, which sometimes dictate how you can make the wine, and which endorse an explicit hierarchy of vineyard sites (some are grand cru, for instance; some merely village), American Viticultural Areas impose no restrictions other than physical boundaries.

To approve an AVA, the Tax and Trade Bureau requires evidence that the area in question is geographically distinct from its immediate surroundings. Consider Healdsburg’s Russian River and Dry Creek valleys: Though adjacent, the former gets shrouded in fog, the latter pounded relentlessly by sun, and as a result they grow different grape varieties (Pinot and Zinfandel, respectively).

“When people talk about Petaluma Gap, the wind is the first thing that comes up,” said Doug Cover, a home winemaker in Petaluma who drafted the petition on behalf of the Winegrowers Alliance. Even the AVA’s name is a reference to what’s called the wind gap. “The major cooling influence isn’t the fog, like a lot of people think, but the wind tunnel.”

Wind blows in from the Pacific Ocean and funnels through this low-lying gap, nestled among coastal mountain ranges, until it hits Sonoma Mountain. A powerful wind continues to channel south toward San Pablo Bay. As in Santa Barbara’s Santa Rita Hills, the wind pattern runs west to east, as opposed to north to south — rare for California.

High winds can lead to smaller berries and thicker skins, which affect the wine’s skin-to-juice ratio. Crucially, the vineyards included in the Petaluma Gap’s boundaries get afternoon winds of at least 8 mph for much of the growing season. Cover cites studies that show 8-mph winds to be the threshold for stomatal conductance. In other words, high-speed winds can actually cause the plant stomata to close, slowing photosynthesis. That can result in a longer hang time for the grape: more flavor development.

The terrain has its challenges. Extremely poor clay soils dominate the San Pablo Bay-adjacent southern portions, which used to be marshland. The western extremities of the proposed AVA are probably too rugged for grape-growing, excessively cold and brutally windy.

The Petaluma Gap’s sweet spots are its eastern edges, near Sonoma Mountain, Bennett Valley and Carneros. The area’s Chardonnays generally show yellow apple, baked pear, lemon, salinity. Many of the Pinot Noirs feature lush, opulent black and red fruit.

“We get the triumvirate,” said Evan Pontoriero of Fogline Vineyards. “Great natural acidity, concentration of flavors and lower alcohol.”