Another early adopter here is Paul Otellini, who retired as chief executive of Intel a couple of years ago. He and his wife, Sandy, are partners with the American Truffle Company and planted 1,500 to 2,000 nut and oak trees in 2011. “The demand seems very solid,” Mr. Otellini said.

The company has also planted orchards in Sonoma and in North Carolina, Alabama, and Ontario. This winter, farms in Kentucky and New Jersey will plant trees. But the company has focused much of its efforts on Napa Valley, with its constellation of high-end vineyard owners, chefs and other foodies.

One of the largest Perigord producers in the world is the Truffle and Wine Company, in the fertile valley of Manjimup in Western Australia. The company produces about seven tons of highly acclaimed winter truffles a year. It’s a model for what Mr. Chang, 45, and Dr. Thomas, 35, hope to achieve in Napa: a farm that grows a combination of wine grapes and truffles.

Each acre of truffle orchard can produce 30 to 50 pounds or more of Perigords and can earn seven times or more what an acre of wine grapes does. But it takes a minimum of five years for truffles to begin emerging after the trees are planted, and seven to 11 years to achieve peak production.

Truffles are fungi that process nutrients for trees in exchange for sugars secreted by the roots. They start out covering the roots as a glove covers fingers, and send threads into the soil that form larger masses that become truffles. Perigord truffles — black, knobby and redolent — are found a few inches underground and can range from as small as marbles to as large as softballs. Also called black truffles or winter truffles, they sell for top dollar at the peak of the season, wintertime, when the flavor is richest.

Only the white Alba truffle, which grows wild in Italy and has so far defied domestication, fetches more — up to $2,000 to $3,000 a pound. In 2014, a four-pound-plus white truffle sold at a Sotheby’s auction for more than $61,000 for its unusual size as well as its flavor. Another high-end variety, Burgundy truffles, bring $300 to $600 a pound, but trees produce two or three times as many of them. The prized black truffles once grew only in the Perigord region of France. But France figured out how to domesticate them 40 years ago. Now most French Perigords are farmed and are no longer gathered wild.

As a child, Dr. Thomas loved foraging for nuts and berries at his Manchester, England, home, and was particularly entranced by fungus. “Mushrooms are so bizarre — they appear for a few days, and then they’re gone — and it quite fascinated me,” he said. He learned about truffles while studying the methods that plants use to send messages to one another, called signaling. Mycorrhizae (the technical name for the fungi) assist in plant-to-plant communication. “It was like James Cameron’s ‘Avatar,’ here on Earth,” he said, referring to the sci-fi movie.