On a bright and chilly autumn morning, 30 or so outdoorsy types are huddled in a parking lot at the Fermilab nature area in suburban Batavia, walking sticks and wicker baskets in hand. The ragtag crew ranges from boomers in smart L.L.Bean attire to younger folks with a crunchy Birkenstock vibe. On the periphery, a pair of women in puffy jackets take turns dousing each other with bug spray. It’s a good crowd for the Illinois Mycological Association’s last mushroom hunt of the season.

A lanky 60-year-old with a salt-and-pepper beard steps toward the middle of the group. He wears tattered jeans and a Columbia jacket that’s seen better days. Patrick Leacock is the club’s president and, not for nothing, a rock star in the field of mycology, or the study of fungi. In a placid voice, he delivers a brief, if less than rousing, pregame pep talk: “There’s no rule what to leave and what to pick. Just try to pick good stuff in good condition. What we don’t want are big clods of dirt—it gets all over everything.”

Dipping into his backpack, he doles out maps along with a dense one-sheeter that reminds me of a science nerd’s version of an NCAA March Madness bracket. The page, filled with scientific names that look like alphabet soup to anyone who didn’t study Latin, details the more than 80 distinct species of regional fungi previously found at this location.

“Now, a lot of people are going to find the same stuff,” Leacock continues. “But everyone is also going to probably find something that’s different than what somebody else found. There’s no way to know what everybody is finding unless, you know, we all had implants in our heads.” He pauses for comic effect. “That’s coming next year.” His dystopian wisecrack gets surprisingly hearty laughs.

Finally, the hunt begins. The mushroom enthusiasts—just a small cross-section of the 200-member club—fan out into the woods of the 6,800-acre Fermilab campus, with a sizable contingent following hopefully in Leacock’s wake as he methodically scans the ground for a specimen worthy of his attention. After a minute or two, he spots something and scampers away from the group. He returns a few seconds later holding a tree branch speckled with delicate cream-colored caps.

“Oh, cool!” says a young woman in a red pea coat. A long-haired rocker type strides over to gawk as well.

“This is different from the polypore we saw earlier,” Leacock declares, referring to a type of fungus that holds its spores—a mushroom’s reproductive apparatus—in tube-like structures on its underside.

Leacock plucks off a mushroom, smells it, and holds it up as if he were a jeweler checking the clarity of a diamond. As he drops the sample into his bag, a blond woman wielding a small knife saunters up and asks him the question he hears more often than any other.

“Is it edible?”

Though Leacock has reminded his flock that the purpose of the club’s forays is scientific and not gastronomic, on this excursion alone he will be asked that same question at least a dozen times. He understands. Until he became lactose intolerant a few years ago, he loved cream of morel soup as much as the next guy.

Still, a little respect for the science would be nice. Leacock, who has been affiliated with the Field Museum since 1997, is one of the country’s foremost experts on fungi, a dogged researcher with a doctorate in plant biology who can rattle off details about gill structure and spore production with the ease of a true savant. His renowned ability to discern subtle differences among species using just his senses makes him in demand nationwide for research projects and conservation efforts.

Last fall, Leacock achieved something virtually unheard of in the field of mycology: fame. Or at least what passes for it in his line of work. In an unexpected publicity coup, he and several colleagues announced the discovery of a new species of chanterelle found predominantly in northeastern Illinois, southern Wisconsin, and northwestern Indiana. They decided to name the newly identified mushroom—which had likely always been growing in our midst but had hitherto been lumped in with similar-looking chanterelles until Leacock spotted a distinction—after Chicago.

While the revelation of a new species of fungus isn’t exceedingly rare, this one, because of the mushroom’s pedigree, caused a local stir. The news about Cantharellus chicagoensis—covered in the Reader and on Chicago Tonight, among other outlets—turned a spotlight on Leacock’s work and on local mushroom seekers in general. And, for laypeople at least, the discovery shed light on an overlooked truth about Chicago: It’s one of the more diverse mushroom habitats in the country—a region where Eastern deciduous forests meet the prairie, creating a varied geography characterized by glacial soils, forests, swamps, and bogs that together constitute a very comfortable home for fungi. With 1,200 species confirmed in the greater Chicago area alone—in city parks, in county forest preserves, even at the edges of weedy parking lots—fungi are literally all around us. All we have to do is look.

In many ways, mushroom hunting is akin to bird watching, another pursuit built around sightings, cataloging, and life lists. In fact, when Leacock—a native of Minnesota—was 14, he joined the local chapter of the National Audubon Society and instantly got hooked on birding. For Minnesota bird sightings, he recalls, “the big number to hit was 300. And I got to 302.”

Observation, identification, classification—these became Leacock’s passions. After graduating from the University of Minnesota in 1979, he stayed involved with the Audubon Society and other conservation clubs while working various restaurant jobs and, for a spell, doing clerical work for an insurance company. (For a year and a half in his 20s, he lived in Arizona, working at a coffee shop at Grand Canyon National Park.) “I kind of became disjointed from people my own age,” he says, “because I was always out bird-watching with retirees.”

It was while looking for warblers in Minnesota’s Itasca State Park that Leacock spotted his first morel, the honeycombed mushroom that appears for a few fleeting weeks in spring and is often called a gateway drug for future fungi fanatics. (Before then, his only exposure to mushrooms had been the rubbery canned ones his parents tried to get him to eat at dinner.) Soon enough, Leacock had traded his binoculars for a mushroom basket—though birding remains in his blood: “I can still hear them, I can still recognize them. But they’re kind of in the background now.”

While birds have always enjoyed a special cachet among naturalists, fungi were long the Rodney Dangerfields of the botanical world, not receiving their due until 1969, when they stopped being classified as “lower plants” and were enshrined in their own kingdom, one distinct from both plants and animals. Unlike plants, fungi do not contain chlorophyll and do not photosynthesize. They get their nutrients by serving as nature’s recyclers, processing dead plant matter, such as rotten tree branches and moldering leaves. The magic starts underground, as the vegetative part of the fungus, known as the mycelium, absorbs nutrients from its surroundings until—boom!—a mushroom pops up, in a process whimsically called fruiting. Scientists estimate that there are more than a million species of fungi, though only 100,000 or so have been cataloged scientifically and given names.

Mycology is still a relatively small field. In fact, so few people have studied mushrooms over the years that there’s a dearth of historical data for researchers to base their work on. “What sets fungi apart is they are ephemeral,” says Greg Mueller, the former head of the botany department at the Field Museum and currently the lead scientist for the Chicago Botanic Garden. “Finding them is like a treasure hunt. That’s the exciting part. But they’re not always there. That’s the challenge. And it chases some people away.

Even for a mycologist with the undisputed bona fides of Leacock, finding steady work can be catch-as-catch-can. His career is a patchwork of professional affiliations and consultative work, of which his position at the Field Museum is just the most visible. To make a living, he frequently has to bounce from one extended research project to another, doing things like gauging the impact of air pollution on fungi growth or studying the effects of woodland restoration on local mushroom species. Municipalities will occasionally hire him to do field surveys to assist with preservation efforts.

Among his more interesting roles is serving as an adviser to Chicago’s poison control center, which relies on Leacock when it can’t identify a wild mushroom that has made someone sick. No one has died on Leacock’s watch, he tells me, but one woman did need a liver transplant after eating an innocuous-looking Lepiota subincarnata, a highly toxic gilled mushroom. And then there was the time he had to identify the variety of psychedelic mushroom that had given a suburban teenager a very bad trip.

Mushrooming also dominates Leacock’s limited free time. He keeps a camera set up in his Irving Park apartment to snap photos of the constant flow of specimens from his forays and fieldwork. A few months ago, he started teaching a mycology class at the Art Institute and was an onsite expert at a nature exhibit at the Backroom, an über-cool pop-up bar at the Chicago Athletic Association Hotel. Leacock, who is single, fills his social calendar with mushroom events where he meets up with friends and colleagues from other clubs around the country—sort of like vintage record collectors getting together to scour bins for rarities.

As a field researcher, Leacock is something of an anomaly. These days, taxonomy—the science of classifying organisms—is increasingly shifting away from personal examinations of living things in differentiating their characteristics. DNA analysis is where most of the grant money is going. It’s sexy and high-tech, but it reduces the prestige of researchers like Leacock, who prefer having their faces in the dirt.

The Field Museum has its own DNA lab. A sign above the entrance announces, “DNA Analysis Is Going on Right Here, Right Now.” In the area open to the public, visitors can inspect large three-dimensional double helix displays, and a plastic shark is suspended from the ceiling. (“The person who runs the DNA lab is a shark guy,” Leacock points out.) Inside, white-coated technicians mill about.

In a far corner of the public area stands a narrow glass case. Arrayed along the bottom shelf are several trumpet-shaped mushroom specimens. These are samples of Cantharellus chicagoensis, the illustrious Chicago chanterelle. Leacock explains that the characteristics distinguishing this mushroom from other chanterelles that grow in our region are incredibly subtle: It is slightly smaller, with a green tint around the edge of its cap. It has virtually no aroma, whereas other chanterelles exude a fruity scent. The differences were so hard to discern that Leacock’s colleagues weren’t initially certain he’d identified a new species, but Leacock was adamant.

“I didn’t see the forest for the trees,” says Mueller, describing his reaction when Leacock pointed out the distinctions. “But he convinced me.”

The Chicago chanterelle had more or less been hiding in plain sight. Its identification was the result not of stumbling on a strikingly new specimen but of Leacock deciding to conduct a renewed comparison of specimens he and his colleagues had collected over time. Mueller says that Leacock has an almost preternatural gift for such comparisons. “He has this incredible internal data set in his head. He can say, ‘Well, I know that’s new, because I haven’t seen that before.’ ”

Ultimately, DNA analysis sealed the deal. Leacock and his colleagues ran tissue samples from what he believed to be the distinct species through the Field’s DNA sequencer, then compared the results against the genetic sequencing of other known chanterelles to make the finding official. Leacock dropped the news with an article in the July–August 2016 issue of Mycologia, the official publication of the Mycological Society of America.

Such moments of glory are rare for mycologists. The bulk of their job entails painstaking cataloging and record keeping that goes unnoticed. But Leacock may be poised to change that, too. He is planning to write a full botanical compendium of all the species in the Chicago area. It’s a colossal undertaking, one not attempted since the 1920s, and will require him to merge 20 years’ worth of his own fieldwork—recorded in a research database of more than 53,000 entries—with museum files that go back to the late 19th century.

Leacock’s compendium could be groundbreaking. Mueller says that the data Leacock has been collecting on our region’s mushrooms are much more extensive than the work of his predecessors. Thanks to Leacock’s project, Mueller says, “we have the chance to be one of the best-known regions [for mycology] in the U.S.”

Leacock sees his work as the continuation of that of the turn-of-the-century naturalists who first began documenting the area’s fungi. “I’m old-school,” he says. “I like the fieldwork. Besides, without it, you’d have no DNA to sequence.”

Leacock’s cluttered office in the Field Museum is a testament to his old-school predilections. A map of the Chicago area hangs on the wall. It’s studded with a few dozen colored pushpins indicating where he’s conducted field studies. Specimen boxes line the floor. Leacock opens one and pulls out what looks like a plastic police-evidence bag. In it are a few shriveled mushrooms that were dried in a food dehydrator that resembles a Crock-Pot, sitting on a nearby side table.

Upstairs, in the Field’s fourth-floor herbarium—the museum’s archives of botanical specimens—Leacock walks over to a bank of floor-to-ceiling filing cabinets and spins a crank to slide one of the units aside so he can access a specific drawer. From it he produces a sepia-toned cardboard specimen mount with a label dated 1902. The mushroom on it has deteriorated to nothing more than a rusty spot, but to Leacock it’s proof that this particular life form existed, was seen, and was documented by a naturalist of yore.

“It’s about knowledge,” Leacock says, squinting through his glasses at what’s left of the sample. “It’s our quest to catalog the life on the planet. And this is my little corner of the planet.”

The mushroom hunt at Fermilab concludes with a sort of show-and-tell in the cafeteria of Wilson Hall, the monolithic central building of the vast campus. The fruits of the day’s labor have been spread out on the tables. There’s something for everyone: from the familiar caps and stems of classically shaped mushrooms to alien-looking organisms that resemble brains and blobs and go by names such as “puffball” and “stinkhorn.” Leacock hurriedly tags as many as he can with note cards pulled from a cigar box. His fellow mushroom hunters hover about, snapping photos of various specimens.

Having assessed the group’s haul, Leacock asks for everyone’s attention and, brandishing one mushroom after another, embarks on an hourlong mycology tutorial for his rapt audience. He covers a wide range of mushroom minutiae, from demonstrating how to take a spore print to describing in gripping detail how one particularly charming-looking little brown mushroom (“an LBM,” he jokes)—the deadly Galerina marginata, also known as autumn skullcap—can kill you by releasing toxins that attack the cells in your liver. And as a sop to the foodies in the crowd, he even shares his insights on the texture and flavor of certain mushrooms, pointing out which are best suited for stir-fries and which are better for soups.

Now he holds up a small dark blue mushroom that he says belongs to the genus Cortinarius. He explains that Cortinarius comprises more than 2,000 species, many of them—like the one in his hand—still unclassified. “I’ve got six collections of this, but we don’t have a name for it yet,” he tells the group. “We searched online last year and couldn’t find anything that matched this blue.”

Leacock suddenly appears more animated, more alive. Even after all his years rummaging through forests, bogs, and wetlands for fungi, it’s this potential for experiencing something new that seems to excite him more than anything.

His presentation complete, Leacock is mobbed by people with burning questions about their finds. I half expect a few of them to ask Leacock to sign their mushroom cap. Just as he seems on the verge of calling it a day, he spies a small gray mushroom in the hands of a woman in rubber boots a few paces away.

“Oh, that one’s cute,” he says (of the mushroom, presumably). He remarks on the powdery residue on its surface. Gently, but without asking, he exercises his professional prerogative, taking the mushroom from its owner and placing it in his specimen bag so he can take it with him for further study.