Beneath a row of fir trees River Shannon Aloia walks along a remote dirt road on national forest land, scanning the ground for morels.

“Find it,” she commands her dog, Jasper.

The search pays off for Ms. Aloia, an avid forager: She spies a solitary honey-colored morel, and plucks it.

“Foraging changes your relationship with nature,” she said. “You are out in the woods using all of your senses. And it’s gratifying when you can identify something and take it home and prepare it for your family.”

Spring in the northern hemisphere is a favorite time of year for foragers like Ms. Aloia. It is especially popular in the American West because of the millions of acres of publicly owned lands that give foragers the freedom to roam and harvest to their liking.

Once the snow melts, a variety of fungi begin popping their heads above ground — oyster mushrooms, king boletes and several types of morels. A profusion of flowers and other edible and medicinal plants, including wild onions and asparagus, fiddleheads, nettles and miner’s lettuce, are also highly sought.

Come summer, the berry crop beckons in the Rocky Mountain West: chokecherries, wild strawberries and plump, purple huckleberries. In late summer and fall, other wild crops emerge, such as piñon or pine nuts in the Southwest and mushrooms like chicken of the woods, shaggy manes and the prized matsutake.

Although most national parks ban commercial foraging, about three-fourths allow people to explore and collect their favorite crops for personal use. Individual parks set limits each year, some like Death Valley in California and Nevada restrict the collection of foods like nuts and berries to a quart a day, and only for personal consumption. Foraging is banned altogether in about a quarter of all national parks.

But things are changing in the woods, worrying those who for years have enjoyed the seasonal taste of food growing in the wild and foraging’s connection to centuries of dependence on natural habitats.

Foraging has grown so popular since the pandemic that state and federal agencies are weighing whether to impose additional restrictions.

Some leading foragers, for both personal and commercial food, say more public lands are being declared off limits, especially in places where wildfires have devastated the forest lands.

Their concern is based on the increasingly popular attraction to a striking ecological phenomenon: Charred landscapes and disturbed grounds provide ideal conditions for morels to flourish in plentiful numbers. That has attracted bigger and bigger crowds that swarm burned lands in the spring following a previous year’s big forest fire, and the foraging numbers have grown far too large to manage, officials say.

“Here in Oregon, they rarely closed burns before the pandemic,” said Trent Blizzard, president of the North American Mycological Association, who with his wife Kristen, runs The Modern Forager website. “But for the last three or four years, they have closed most of the fires, including all of the big ones.”

“We’re concerned about foraging access to all state and federal land, not just burns,” he said. Decisions on where and when to close national forest land are made at a local level. David Lawrence, special products program manager for the national office of the U.S. Forest Service, said that administering the commercial harvesting of any product was often low on the list of priorities. Some foragers who sell their foods are required to obtain permits.

“The first step is to ensure sustainable management,” he said. That might require historical and environmental analysis for commercial mushroom picking, or the deployment of law enforcement to manage large crowds that can lead to closures if there aren’t enough resources.

“I’ve seen that being a barrier to offering permits,” he said.

It’s not uncommon to have hundreds of commercial pickers show up for a giant flush of burn morels. At the matsutake harvest in Oregon, thousands have descended.

David Haupt, an official with the regional office of the U.S. Forest Service that includes Montana, Idaho, parts of North Dakota and Washington State, said no commercial mushroom gathering permits had been issued this year partly due to the size of the crowds that had showed up in the past to gather them. “Reduction of potential environmental damage is a top consideration when assessing applications for commercial permitting,” he said.

Other hazards have raised concerns, especially since all morels produced in the United States are gathered in the wild, not cultivated.

In May, Montana health officials warned residents about the dangers of morels after a series of illnesses and deaths. In the spring of 2023, 50 people were sickened and two died in Bozeman, apparently from morels that had been cultivated in China and shipped to a local restaurant. A Missoula lawyer died on a river rafting trip after he ate morels that he foraged.

Morels contain a toxic compound called hydrazine, and other mushrooms can also be poisonous. In the United States, few deaths occur annually from deadly mushrooms although dozens of people do become ill and recover each year.

Dennis E. Desjardin, a professor emeritus at San Francisco State University who has studied the ecology and evolution of fungi for over 40 years, said sellers of wild mushrooms should include instructions for consumption.

“The F.D.A. should require the posting of a warning that wild mushrooms should be thoroughly cooked before eating, especially morels, which are toxic when ingested raw,” he said.

Although foraging, especially for mushrooms, isn’t a new pastime, the pandemic fueled a quest for outdoor experiences. Traffic soared and the spotting of bountiful sites spread via social media.

“The number of people foraging exploded in number,” Ms. Aloia said. “Everybody wanted to go to the places that are easy to get to, and those places are wiped out. Then they go on to the next place and the next place.”

Ms. Aloia oversees a Facebook group devoted to foraging. She said newcomers didn’t always understand the unwritten etiquette of foraging, and many gave away “honey holes” — places rich in mushrooms — on social media. Or, she said, they invaded places that, while on public lands, others had long considered their sacred, secret spots.

“There has been a lot of claim jumping,” she said.

“The learning curve of what used to be esoteric knowledge, which took years to cobble together, has been flattened by social media,” said Langdon Cook, who teaches foraging in the Seattle region and who wrote “The Mushroom Hunters,” a book about the underground subculture of commercial foragers. “You can even get coordinates as a first-time picker out there, finding mushroom species that maybe in the past it took amateurs years to figure out.”

Uncontrolled crowds have prompted those trying to rein in foragers to take action. Because of soaring numbers, Salt Point, the only state park in California that allows mushroom foraging, recently lowered its collection limit to two pounds per person from five pounds. Minnesota is considering new restrictions on gathering mushrooms in state parks for personal use, too.

Climate change is also upending some aspects of mushrooming. “The number of species and abundance has diminished quite a bit,” Dr. Desjardin said. “And it’s gotten drier and the season has gotten later.”

This is the time of year when morels and other foraged ingredients make their way to the table.

“A lot of menus have morels on them because the season’s just kicking in,” said Chris DiMaio, a chef in Whitefish, Montana. “We went out a few days ago and picked a few pounds, and I’ll incorporate them into this weekend’s menus.”

Urban foraging has long been popular, too. The well-known “Wildman” Steve Brill has taught the practice in Central Park for decades, and a group in Los Angeles called Hollywood Orchard gathers fruit that grows in abundance and often goes to waste, and preserves it in pop-up kitchens to donate to local charities.

Indigenous and Native American tribes have long embraced foraging as a way to healthier diets and as part of a food sovereignty movement to restore traditional foods. Some studies suggest that eating wild foods can provide essential nutrients.

“With food sovereignty, we are looking at the ability to put healthy foods and ancestral foods, which we used to survive for thousands of years, back on the table,” said Jill Falcon Ramaker, an assistant professor of community nutrition and sustainable food systems at Montana State University.

Sean Sherman, known as the Sioux Chef, and the founder of the Indigenous restaurant Owamni in Minneapolis, is among those who are adapting foraged food for the modern palate.

“We’re not cooking like it’s 1491,” Mr. Sherman said in an interview on NPR’s “Fresh Air,” referring to the period before European colonization. Two signature dishes that rely on foraging are roast turkey with a berry-mint sauce and black walnuts and a wild rice pilaf with wild mushrooms, cranberries and chestnuts.

Mushrooms still get most of the attention from the foraging community. “Everybody wants to find fungi these days,” said Mr. Cook, the author and Seattle forager. “They’re sexy and hip and the poster child for foraging.”

Fungi play a key role in natural systems, and they have a symbiotic relationship with the forest. Some are the product of a vast web of mycelium that laces tree roots and that gathers water and nutrients and shuttles it to the tree in exchange for sugar. The mushrooms pop to the surface where they release spores that are borne by the wind, as part of mycelium reproduction. Other fungi break down dead plant material and send jolts of phosphorous and nitrogen into the roots of growing trees.

Picking mushrooms does not harm the forest or future mushroom harvests, as long as the underground mycelium is not damaged. “The only thing that would be adverse is that you are also removing a food source of lots of insects and other small animals and deer that feed on them,” Dr. Desjardin said.

Foraged produce can be pricey. Wild chanterelles were recently selling for $32 a pound at Far West Fungi, a popular mushroom store in San Francisco, while porcinis fetched $56 a pound and morels for $36 per pound.

Another valuable and unusually tasty mushroom is the matsutake, or pine mushroom. They have a distinctive aroma — many compare their smell to a combination of dirty socks and Red Hots candy.Others say the smell is reminiscent of cinnamon, with subtle floral and citrus nuances. They grow in pine forests around the West and can be collected on public lands beneath the pine needles and forest duff beneath pine trees from early September until early November. National forest land near Chemult, Ore., is one of the premier spots for pickers who come from around the country to harvest them during the two-month-long season.

There is a Mushroom Trail in the West that itinerant pickers follow seasonally, a path Mr. Cook has written about.

If you drew a circle around the Pacific Northwest and into British Columbia and the Yukon, “you could pick mushrooms somewhere inside that circle every day of the year,” Mr. Cook said.