Staci O’Toole is lying face down in the dirt. “I can smell it!” she cries, nose to the roots of a hazelnut tree.

A funky, fungal odor emanates from a shallow hole in the ground of this Sonoma Valley orchard. It hints at a hidden treasure many years in the making: a French Périgord truffle, grown right here in California.

Commonly known as black truffles or even black diamonds, Périgords are one of the world’s most sought-after delicacies, selling for $800 or more per pound. Revered for lending an intoxicating flavor to everything from tagliatelle to sushi, they remain widely adored and shrouded in mystery.

With wild truffles increasingly scarce, scenes of affable farmers trawling the woods with a pot-bellied pig are becoming a rare sight. Most black truffles these days come from farms, where they are hunted by specially trained dogs. Cultivation secrets in this lucrative industry have traditionally been closely guarded, with the market dominated by France, Italy and Spain. But in recent years New World upstarts have been gaining ground: Australia is expected to produce 15 metric tons this year, while New Zealand, South Africa and Chile all have burgeoning industries.

For decades many have pinned their hopes on the Mediterranean climate, robust wine industry and thriving food scene of California as the world’s next truffle hotspot. Now, it appears, such hopes are paying off.

O’Toole and her truffle-hunting dogs in Santa Rosa. Photograph: Talia Herman/The Guardian

‘The birth of an industry’

On this bright winter day, O’Toole, AKA the Truffle Huntress, has brought her pedigree truffle dogs to survey a property in the heart of northern California’s wine country. Mila, the more experienced of the lagotto Romagnolo dogs, is leading the charge. Panettone, still in training, bounds close behind.

The pair survey the orchard with enthusiasm and ruthless efficiency: several quick sniffs at the base of a tree are enough to determine whether a truffle lurks beneath. They comb several rows of trees without luck before Mila pounces and paws at the ground: the sign to start digging.

Wearing knee-high wellies and oversized sunglasses, O’Toole uses a delicate truffle trowel, a tool that looks more like a blunt dagger than a shovel, to turn the soil, occasionally lowering herself to the ground to sniff at her progress. “I can tell if I’ve got something here because it will make my mouth start watering,” she explains, brimming with optimism.

Truffles can take up to 10 years to produce, and growing them is like farming in the dark: fiddling at the surface in the hopes something magic is taking root below.

O’Toole came to truffle hunting after a career as a health insurance executive living in Silicon Valley. She wasn’t ready to retire but wasn’t sure what to do next.

Turned out her dog held the key. The lagotto Romagnolo is a traditional Italian truffle hunting breed so attuned to its craft that, when she bought Mila from the breeder, they made her promise she would train it up properly. Mila was a natural, finding her first truffle at just 12 weeks old. O’Toole now works as a hunter on various orchards while running her own farm, which this year harvested almost 2lb.

O’Toole had ‘Truffle Huntress’ sewn on to her shirt. Photograph: Talia Herman/The Guardian

She is hardly alone. The orchard where I met her belongs to Harshal Sanghavi and Matt Hicks, a San Francisco couple who harvested their first truffle just before Christmas. The Sonoma winery Jackson Family Wines, meanwhile, found its first truffles in 2017 and this year hauled out slightly over 30lb.

“We’re witnessing the birth of an industry,” says Charles Lefevre, a longtime truffle consultant and the founder of New World Truffieres. Lefevre’s Oregon-based company sells trees whose roots have been inoculated with the black truffle fungus. When he started in the early 2000s, Lefevre recorded small flurries of success in places such as Idaho and Tennessee.

The truffle industry, he says, is no longer just a pipe dream but is seeing “exponential growth”. Of his 22 farms now in production, 10 have harvested their first truffles within the last two years. It may be the start of something big.

A truffle, sliced in half, at a Jackson Family Wines property. Photograph: Talia Herman/The Guardian

‘We proved them wrong’

The quest to grow truffles in California began decades ago when William Griner, a Vietnam veteran turned pot farmer, took a leap of faith and bought 100 hazelnut trees inoculated with the truffle fungus from a young Frenchman named François Picart.

Picart had arrived in California in the mid-1970s, determined to sell “truffle trees” and help America embrace truffle agriculture. He ultimately found few buyers, returned to France frustrated and went on to launch a highly successful chain of American-themed barbecue restaurants.

But Griner’s gamble paid off. He cultivated what is considered the first truffle ever grown in North America in 1987. His farm, Mendocino Black Diamonds, would go on to produce 35lb of truffles a year until his death in 2008.

“California really was the first state to get involved in growing truffles in North America,” says Griner’s old friend Todd Spanier.

Spanier, who founded California Truffle Orchards, a farm management company, sees clear parallels between the birth of the Napa Valley wine industry, originally viewed with skepticism by Europe, and the truffle pioneers of today. “In the 1970s we had the French saying: ‘No one can grow wine outside of France.’ And we proved them wrong,” he said.

A truffle hunter shows off his harvest. Photograph: Talia Herman/The Guardian

Since then, truffle farming’s bohemian origins have been replaced by an ambitious entrepreneurialism with a distinctly Silicon Valley edge. Truffle fever has taken root not just among professional farmers but many first-timers, bringing new players and new ideas to the industry.

Take Dr Paul Thomas and Robert Chang, a mycology scientist and a former tech executive who are building a giant database of truffle knowledge. Thomas had founded a UK-based truffle research company, Mycorrhizal Systems LTD, before teaming up with Chang for a new venture: the American Truffle Company. Now with orchards in the US and more than 20 other countries, this network feeds real-time information about climate, soil and irrigation back to their server in the Bay Area. “This is the big data of truffles,” Chang likes to say.

Truffle farmers now benefit from two major festivals – the Oregon truffle festival, founded by Lefevre in 2006, and the Napa truffle festival, founded by the American Truffle Company in 2010 – which provide a platform to mingle, learn and share breakthroughs.

“In Italy and France it’s all very secretive, but here it’s much more collaborative,” says O’Toole. “That’s why we’re having so much success. The California way is kind of different: we all share data. We are trying to build an industry.”

Farmers are encouraged by the prospect of serving the state’s ambitious dining scene, and in this regard time is on their side. A truffle’s odor and flavor drops precipitously once it’s out of the ground; a good truffle should be served within a week.

Jackson Family Wines, currently the jewel in California’s truffle crown, produced so many this year that it sold the extras to several Michelin-starred San Francisco restaurants. The winery’s executive chef, Justin Wrangler, says it has more demand than it can meet.

Justin Wrangler, the executive chief at Jackson Family Wines, and his daughter Delanie, nine, cook pasta with truffles, butter and cheese in Santa Rosa. Photograph: Talia Herman/The Guardian

A tipping point

It’s hard to imagine California’s truffles will stay secret for long. Rivalling Europe in volume won’t happen overnight, and many who have planted truffles are still waiting for results. But the mood is one of cautious optimism.

O’Toole’s truffle hunting expedition that day comes late in the season, but she’s confident there’s more to be found on the Jackson Family Wines property.

She heads out with her dogs, Wrangler, and the farm’s manager. In the end, the afternoon yields a couple of small truffles. Specimens found several days prior, however, are truly monumental.

From a ziplock bag, Wrangler produces an inky orb as thick as two tangerines. A portable burner is plugged in, red wine swiftly poured, and before long the chef is tossing slabs of truffle butter through hot pasta. He shaves a black cloud over each bowl before we slurp it up. O’Toole raises her glass to toast the moment: “This is what it’s all about.”