Meet Your Neighbors

Foxfire Mushrooms:
Haunted Fungi

The glow of honey mushroom hyphae

The glow of honey mushroom hyphae

Photo: John Denk

Glow-in-the dark woods?! Must be Halloween. But unlike the ghosts, witches, and goblins supposedly floating in the air during autumn, glow-in-the-dark woods are real--and you can find them in Chicago Wilderness.

The glow comes from two native fungi, the honey mushroom (Armillaria mellea) and the Jack o' lantern mushroom (Omphalotus illudens). Your best chance to see these ghost-like fungi is in local oak woodlands.

The glow, popularly called foxfire, comes from bioluminescence, the same chemical reaction that occurs in a firefly. Oxygen combines with a substance called luciferin (also a bit fiendish, no?) to convert chemical energy into light energy.

Magical, glowing mushrooms have been described in literature since 382 B.C. when Aristotle wrote about "luminous wood." Mark Twain described the luminescent mushroom in the Adventures of Huckleberry Finn as "rotten chunks...that just makes a soft kind of glow when you lay them in a dark place."

Some 30 to 40 types of glowing fungus have been described in the world. The two most visible species in the Chicago Wilderness region actually glow in different ways. Bioluminescence occurs in the mycelium of the honey mushroom. The mycelium is the group of tentacle-like structures or hyphae that grow underground and into rotting wood, such as dying tree roots and downed logs. The fruiting body, or the mushroom, is above ground. When the mycelium glows, it appears as if the wood is burning from within.

"The honey mushroom is bright enough to see in the woods on a moonless or cloudy night in autumn," says Greg Mueller, mycologist at The Field Museum. "That's when people call and tell me that their wood piles are glowing." Mueller jokes that he saved taxpayers lots of money once when he convinced officials not to send a hazardous materials team out to a park that was "glowing in the dark."

Aging Jack o'lanterns

Aging Jack o'lanterns

Photo: Bill Beatty/AKM Images, Inc.

The Jack o' lantern's luminescence comes from its gills, the underpart of the fruiting body. During the day, you'll instantly understand the common name of this species. "A large group of cup-like pumpkin-colored fungi grows at the base of a tree," says Mueller. He has taken specimens into a dark room and waited for his eyes to get adjusted; then, suddenly there's a glowing green "being" in the room with him. "The Jack o' lantern mushroom is a decomposer," he says. "It helps restore nutrients to the soil."

But beware! Do not pick or eat the Jack o' lantern, which can cause major gastrointestinal problems. Mueller says he gets calls every fall from the Illinois Poison Control Center about someone who has mistakenly eaten them.

Scientists continue to debate why certain fungi glow in the dark. "Fungal luminescence consumes very little energy and may have no ecological value," writes Nicholas P. Money in Mr. Bloomfield's Orchard: The mysterious world of mushrooms, molds, and mycologists. But, he writes, some "have speculated that glowing fruiting bodies might attract insects that would serve as vectors for spore dispersal."

According to University of Wisconsin mycologist Tom Volk, the glow of the Jack o' lantern's fruiting body is the result of the fungus clearing byproducts of metabolism--luciferases--from its mycelium. "Putting the wastes into the above-ground fruiting structure," he writes, "is the fungus' way of getting rid of its waste products."

Mushrooms may glow in the dark to make sure they and their species survive. But, just maybe, it's also to create a mysterious shine in the woods at the time of year when our thoughts turn to ghosts.

— Sheryl DeVore

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