By Julia van der Vink
July 24, 2013

FORTUNE — Fifty miles northwest of Napa’s bright lights and gilded estates, a California flag hangs from the ceiling inside an old apple-processing plant. Led Zeppelin plays from the speakers while a Jack Russell named Jim darts around the fermentation tanks. If you’re looking for a trophy Cabernet, you’ve come to the wrong place. Forgoing Cabernet Sauvignon for grapes like Trousseau Gris and Valdiguié, a handful of renegade winemakers have begun experimenting with heirloom grape varieties from many of California’s oldest vineyards to produce some of the most compelling wines to come out of the state in decades.

Winemakers Pax Mahle, Scott Schultz, and husband and wife duo Ryan and Megan Glaab share ideas and equipment to make wine under their respective labels: Wind Gap, Jolie-Laide, and Ryme Cellars. “California is so diverse, it makes sense to grow different grape varieties, not just Cab and Chardonnay,” says Mahle. He and Schultz both make wine from Trousseau Gris, a grape that traditionally hails from Alsace-Lorraine. Though the variety has been widely planted in California since the early 20th century, today only one vineyard block remains standing in the Russian River Valley.

Though mainstream trends would make you think otherwise, “these grapes aren’t that esoteric,” says Chris Brockway, who runs his one-man urban winery, Broc Cellars, out of a warehouse in Berkeley, “they’ve been in California for years.” Though Brockway works with grapes as unusual as Valdiguié, he is quick to point out that the variety has been planted in California since the mid-1900’s. Brockway is particularly sentimental about his Carignan, which comes from 130-year-old vines in the Alexander Valley, north of Napa. “The Carignan vineyard was planted in 1879. Someone was going to tear it out and plant Cabernet Sauvignon. It’s a part of California history! I thought, ‘What do I have to do to save this?’” The fruit from the 1879 vineyard soon became the backbone of Brockway’s flagship wine.

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There are tiny vestiges of California’s early grape-growing history planted across the state if you know where to look. A 93-year-old man who planted Valdiguié vines next to his house in Calistoga with his father back in the 1960’s. Two Italian siblings who brought over Barbera from their backyard and planted it in the Sierra foothills to remind them of home. An old farmer who lives on a plot of Mourvèdre in Medocino that he has neglected for years. The winemakers who source grapes from these idiosyncratic diamonds in the rough are striving to resurrect the diverse viticultural traditions of the growers that came before them. In turn, they are making wines that are a commemoration of California’s immigrant heritage; they are a re-imagination of California’s viticultural potential; and they are a tribute to the unknown growers who had either the foresight or the foolishness to plant these unusual grapes in California in the first place.

According to Sam Bilbro of the winery Idlewild, today 93% of all of Northern California’s viticultural acreage is planted with the same eight major grape varieties. “But it is a myth that these are the only grapes that can do well here. In the last fifty years, many of the lesser-known varieties that make up the remaining 7% have become almost commercially non-existent. We’re trying to change that.”

Last year, winemaker Matthew Rorick of Forlorn Hope tried to narrow his focus down to four grapes. He ended up working with 21 different varieties. “I’ll get a call saying, ‘I found somebody growing Picpoul.’ How can I say no to that?!”

With equal parts playfulness and die-hard romanticism, Rorick has a soft spot for the lesser-known underdog grapes that pay homage to California’s viticultural heritage. “Many obscure grapes exist in California because immigrants brought them over and planted them in their backyards. As an immigrant country, isn’t having an eclectic selection of grapes what California is all about?” Rorick is currently leaving his own footprint by planting a new vineyard with a field blend of Trousseau Gris, Chenin Blanc, Green Hungarian, Putzscheere, and Chasselas.

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For newcomer Hardy Wallace [pictured], who began Dirty and Rowdy Family Winery with his wife and best friends in2010 after dropping a job in tech sales in 2009, relentless experimentation has gone hand in hand with his learn-as-you-go approach to winemaking. His flagship wines come from three old vineyards of Mourvèdre that he and his wife, Kate Graham have resuscitated. Combining ancient vines with a high-risk approach to winemaking, the wines are fermented using a technique that has traditionally only been used on Gamay grapes in the French region of Beaujolais. “We didn’t know of anyone who had ever tried to ferment Mourvédre that way,” says Wallace. “We took a risk because we were too ignorant to know whether or not it could be done.” Three years after their first vintage, they can hardly keep up with demand. Dirty and Rowdy sold all of their 2011 production in three weeks.

Within this grassroots movement, the winemakers would rather keep their wines accessible than rake in a bigger profit margin. Most of their wines ring in between $20-$30. “Wines should be on the table. They should be part of life,” says Dan Petroski, winemaker at Massican. With bootstrapped operations across the board, “having a model hinged on direct sales is the only way to keep business viable.” The goal of these wines is to have consumers experiment with them. “Wine shouldn’t be put on a pedestal,” says Petroski. “Wine should be personal.”

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