CORVALLIS, Ore. — On a crisp February morning, about 60 people plodded through an orchard that grower Kathleen Sedehi had established for cultivating truffles, edible subterranean fungi widely prized as a food delicacy.

The group was on a field trip during the Oregon Truffle Festival. Attendees were learning to produce truffles by encouraging natural symbiosis between trees and fungi.

“There is such a demand for truffles,” said Sedehi. “It’s exciting.”

Truffles are successfully grown in many countries, said Connie Green, a purveyor of truffles to high-end restaurants. In the Northern Hemisphere, France, Spain, Italy, Croatia, Bulgaria, Romania, England and Turkey have truffle industries. In the Southern Hemisphere, producing countries include Australia, Tasmania, New Zealand, Chile, Argentina and South Africa.

In North America, the industry is young. Growers are pioneers in what is still an experimental space. Experts predict many people won’t jump into the industry until early adopters can prove that the economic benefits of cultivating truffles outweigh the risks.

America’s truffle industry, though highly niche, is gradually gaining momentum.

Charles Lefevre, owner of New World Truffieres Inc. and founder of the Oregon Truffle Festival, said there are now dozens of orchards in each of the four Western states. He estimated California has hundreds of acres devoted to truffle cultivation, Oregon and Idaho each have more than 100 acres and Washington has up to 70 acres.

About truffles

According to Shannon Berch, a scientist with British Columbia’s government and adjunct professor at the University of British Columbia, a truffle is the “underground fruiting body of certain fungi.”

Many types of truffles exist, some of which are fit for human consumption. Among culinary varieties, each has a distinct color, flavor and aroma.

Truffles in the wild colonize the roots of many tree species. In the symbiotic relationship, the fungus acts as an extension of the tree’s root system, helping it absorb nutrients and water. In exchange, the tree supplies the fungus with starches and sugars for growth.

Certain animals, including wild boars, help with the natural dispersal process. When truffles ripen, boars sniff them out, dig them up and eat them, depositing spores in new locations and allowing a new generation of truffles to form.

Growers can encourage production by planting trees whose roots have been inoculated with truffle spores in an ideal habitat. Trained dogs are used to sniff out ripe truffles for harvest.

It’s not an industry for the impatient; orchards often do not begin producing truffles until at least five to 10 years after planting, and crop volumes generally increase over time.

Truffle farmers

People from many backgrounds cultivate truffles. Some do it as a retirement project. Others aim to transition away from non-agricultural jobs. Yet others are farmers diversifying their operations.

Mike Davis, who runs a marine construction company, planted hazelnut trees on his property in Arlington, Wash., north of Seattle, about a decade ago.

He spent about $25,000 per acre to establish the orchard. Since then, he has spent $3,000 to $4,000 per acre per year to maintain it.

Davis is in the midst of harvesting truffles and expects a total harvest of about 30 pounds this winter, which he is selling for $500 to $700 per pound.

He also started an agritourism venture in which people pay $250 each to visit his orchard and watch his dogs sniff out truffles with a tour group. This on-farm “experience” sells out every weekend.

Davis said he is making a good profit and expects a full return on his initial investment in three years.

Other growers are just starting out in the business. Kathleen Sedehi is one of them.

Twelve years ago, Sedehi, an accountant, became interested in cultivating truffles while visiting a grower in Australia.

“I always knew I wanted an ag background,” said Sedehi. “I considered other crops. But when I was introduced to truffles, I thought: ‘Oh, this fits the bill because it’s something I can do on a small scale and something I can manage myself.’”

In 2018, after an extensive search, she bought land in Corvallis. She treated the soil in 2019, installed irrigation systems in 2020 and planted host trees — oaks and hazelnuts — in 2021.

Because the trees are young, she still has years to go before harvest, but she is already researching markets and thinking about getting truffle dogs.

“I’m learning so much,” she said.

Cultivating truffles

The Oregon Truffle Festival drew dozens of people from across the West who are interested in growing truffles for a variety of reasons.

A couple with a 12-acre hobby farm are interested in growing a diverse mix of crops, including lavender, olives and truffles.

The executive director of a nonprofit produces wine and grows cider apples on his property and is interested in adding one acre of truffles.

A semi-retired Oregon farming couple with a hay farm and equestrian operation are interested in adding a small truffle orchard to their property for supplemental retirement income.

A Washington tree fruit grower with about 500 acres of apples, cherries and pears is interested in cultivating truffles on a portion of his acreage to diversify his income sources.

A Napa Valley vineyardist recently bought land in the Willamette Valley and learned that some of the trees on the property had been inoculated with truffle spores, so he was at the conference to learn about the industry and decide whether to maintain the trees.

At the festival, about 60 people participated in a two-day workshop on how to cultivate truffles. The workshop covered site evaluation, orchard planning, maintenance, harvest and markets.

Site evaluation

To successfully cultivate truffles, industry experts say it’s important to have the right site.

“Having a soil that’s well-structured is really important,” said Lefevre, of New World Truffieres.

Lefevre recommends growers use remote site evaluation tools, such as the Web Soil Survey platform operated by USDA’s Natural Resources Conservation Service, to analyze soil profiles to determine whether a piece of land is suitable. He recommends growers then hire a soil scientist to evaluate the site in person.

Andy Gallagher, a certified soil scientist, said truffle orchards generally lie in soil ranging from sandy loam to silty clay. The ideal soil texture is “fluffy,” he said — granular or crumbly.

Truffles tend to thrive in soils with high pH levels that are neutral to alkaline in nature rather than acidic, so experts say growers should expect to apply a significant volume of agricultural lime to their soil.

Truffles are an irrigated crop, so growers also need to plant orchards where they have reliable water rights. Experts say spray irrigation is preferable to drip irrigation.

The overall climate matters, too. Truffles tend to perform best in temperate climates. Lefevre suggests growers analyze their region’s temperature extremes charted over time.

Experts say growers should also consider land use history. Ideal previous uses include fallow land, lightly used pastures and hay fields. Potentially problematic sites include those with salt buildup, recent excessive grazing, excessive chemical contamination or recently cleared woodlands.

Experts generally recommend growers build buffer zones around each truffle orchard to prevent cross-contamination between truffle species. The ideal buffer, experts say, is 100 feet, but Lefevre said he has only a 45-foot buffer between truffle varieties.

Host trees, planning

Truffles can form symbiotic relationships with many types of host trees, according to Berch, the scientist from British Columbia.

In North America, common host trees include the European or common hazelnut, the English oak and the evergreen oak, also known as the holly or holm oak.

“Experience is showing there are advantages and disadvantages of each,” said Berch.

Native trees, she said, may be more resistant to pests and diseases, but some are not yet proven to reliably produce truffles.

Because truffle cultivation in North America is still largely experimental, experts’ opinions vary on how far apart to plant trees for truffle cultivation. Most agree that high- and low-density planting models each have their own set of pros and cons.

Lefevre said a north-south orchard orientation appears ideal for climates with hot summers, while an east-west orientation appears preferable for climates with cooler summers.

Maintenance matters

After planting the initial trees, experts say growers should maintain their orchards over time with pest control, weed control, nutritional supplementation, ongoing irrigation and pruning.

One of the major challenges is preventing rodent damage, especially from gophers. Left to their own devices, gophers will browse on tree roots, stressing the trees and preventing truffles from forming.

“Gophers are probably the single biggest challenge for growers on the West Coast,” said Lefevre.

Growers use a variety of tools — including traps, owls and feral cats — to deter gophers.

Many truffle orchards look similar to hazelnut orchards at first glance. Some growers, however, have adopted an integrated “regenerative agriculture” approach to cultivating truffles that involves planting cover crops or native plants around inoculated trees.

According to Christine Fischer, a specialist in mycorrhizal fungi at the Forest Sciences and Technology Centre of Catalonia, some truffle producers in Spain have adopted integrated practices and seen benefits, including fewer insect and disease outbreaks.

One farm, for example, grows rows of lavender between trees in the truffle orchard. The producers sell truffles along with lavender honey and ice cream.

Fischer advised growers to be careful about what they plant around host trees. Some cover crops have natural antifungal properties that could inhibit truffle growth.

Annual harvest

Truffle harvest comes once a year, and the timeframe varies by variety. Some cultivated varieties commonly grown by U.S. producers ripen in the winter and are harvested from December through March.

Many producers use dogs to sniff out the truffles when they are ripe. Some growers train their own dogs, while others hire dog handlers. Any breed of dog can be trained to sniff out truffles; Lefevre said the individual dog’s temperament is more important than the breed. An Italian breed called the Lagotto Romagnolo is a popular choice that some consider the “gold standard.”

“The fun part is harvesting the truffles with your animals,” said Davis, the Washington producer.

Varied markets

Truffles should ideally be packaged and shipped within one day of harvest.

“A fresher truffle is more valuable,” said Lefevre.

Green, the purveyor, said it’s important to make sure truffles are packaged appropriately.

“Packaging is not to be taken lightly,” she said.

Like fruit, truffles fall into different grading categories worth different amounts based on their size and other characteristics.

Truffle cultivators sell into a variety of markets, including to restaurants, wineries and directly to consumers. Some producers even create value-added products such as truffle-infused olive oil.

Davis, the Washington producer, sells his truffles to chefs, restaurant buyers and consumers. He is also exploring value-added products.

“My truffles don’t all make it to market, though. I end up eating a lot of them,” said Davis.

He laughed.

As the group at the Oregon Truffle Festival visited a series of truffle orchards throughout the Willamette Valley, many people expressed their uncertainty about the experimental nature of the industry mingled with excitement about its potential.

One Corvallis farmer said she is excited to experiment with truffle cultivation on a portion of her acreage that is not currently producing anything.

“Right now, it’s a blank canvas,” she said.