Stumble into a circle of mushrooms while out rambling over hill and dale, and who knows what fate may befall you. You might be cursed or eaten by a giant toad, doomed to die young, or endowed with increased fertility. Most likely, you’ll anger the fairies, who’ll render you invisible, trap you inside the ring, and either force you to dance ‘til exhaustion or drag you into their realm. 

If you’re lucky enough to have a friend mount a successful rescue mission, you may find you’ve been away longer than you thought, have no memory of the experience, or crumble to dust upon emerging. But it might not be all bad: if it’s a full moon when you enter the circle, you’ll be blessed with good fortune.    

These are just some of the myriad stories that emerge around mushroom-dotted “fairy rings.” But contrary to popular belief, fairy rings are not the result of fairies, witches, or other supernatural beings dancing and cavorting in circles. 

They form when a fungal spore grows into a mycelium—the underground threads that form a single fungal organism—and sends out a subterranean network of tubular threads called hyphae. The hyphae that make up the mycelium grow evenly in all directions and then produce a near-perfect circle of “fruiting bodies”—mushrooms—above ground. When the central mycelium eventually dies out, the edges keep growing, and the ring gets wider every year. 

Fairy rings are found mostly on grasslands, but can also be spotted in woodlands, living in symbiosis with trees.

A meeting of mycelium

Fairy rings are formed by the union of two mycelia into a singular mycelium. 

“They melt their nuclei, and then live the rest of their life with a divided nucleus,” says Maurizio Zotti, a mycologist and soil community ecologist at the University of Naples Federico II who specializes in plant-fungus interactions. “This is quite amazing because they are able to switch on and switch off a different nucleus of each cell to adapt to any environmental condition.” 

He explains that fairy rings develop only if the soil they consume is homogenous. Their circular formation also improves their chances of surviving potential pathogens.

Fairy ring of mushrooms in the woods.
Fairy rings are commonly found in forests and grasslands. The mushrooms, also known as fruiting bodies, are the reproductive tips of a larger fungus growing underground. PHOTOGRAPH BY MARTIN SHIELDS, SCIENCE PHOTO LIBRARY

It’s not well understood why fairy rings develop, but Zotti is developing a predictive model. “This summer I will take samplings in different areas where they turn up and try to understand the age of the colonies and the geomorphological and environmental conditions,” Zotti explains. “I’m trying to predict where they will form. It’s going to be really tricky.” 

Because we are still coaxing fairy rings to give up their secrets, it’s no surprise that previous generations turned to the supernatural to explain their origins. Fairy rings are found across the globe, and, fascinatingly, nearly every culture also associates them with the supernatural in some way. 

Fertile ground for folklore

Stories about fairy rings date back centuries in Europe, Africa, and North America. They’re also referred to as fairy circles, witches’ rings, or sorcerer’s rings. In Japan, they’re called shiro, which means “white” and “castle,” referring to both the color of the mushrooms and the underground palace they’ve built. Dancing fairies or witches are the most common origin myth, but some cultures believe fairy rings are where the devil placed his milk churn or where a dragon laid their fiery tail.

“Since fairies are the quintessential supernatural agents in the Gaelic world, they would almost inevitably be associated with strange ‘unnatural’ or inexplicable phenomena in the landscape,” explains Barbara Hillers, associate professor of folklore at Indiana University Bloomington. “So it makes complete sense that mushroom rings would be associated with fairies as a kind of etiological explanatory device.”

While fairy ring folklore may be even older, we can date it to at least the 12th century with the Middle English term elferingewort, or elf-ring. Fairy rings themselves can live for hundreds of years, with the oldest found in Belfort, France, measuring nearly a half-mile in diameter and thought to be 700 years old.

Zotti asserts much of what we know about the formation of fairy rings originated in folklore. And some superstitions are rooted in truth. 

In England, it’s believed that building houses in grasslands with fairy rings means the house will never fall down. Zotti says, indeed, houses built on this soil will have no basement moisture problems “because this kind of fungi needs good soil drainage.” 

Dutch shepherds assert the butter will taste bad if they let their cows graze in pastures with fairy rings. “We discovered the reason for this is that inside fairy rings, there is a form of broadleaf plants that release chemicals that are bitter and give this taste to the milk and cheese,” Zotti notes.

Landscapes often evoke the supernatural

According to Hillers, fairies are strongly associated with landscapes in Ireland and Scotland.

Fairies are also frequently connected with mushrooms in folklore, notes Jonny Dillon, an archivist at the Irish National Folklore Collection at University College Dublin, and not in a positive way. “Fungi have long been looked on with a culture of suspicion and skepticism, being popularly associated with the devil, púca, or fairy.”  

Many cultures view mushrooms as eerily uncanny; they erupt in odd places and coalesce into weird shapes; they don’t grow and develop the same way as fruits, vegetables, or other plants. Their potential poisonousness adds to this malevolent reputation. While it’s wise for cultures to be wary of ingesting unknown fungi, mushrooms are a key part of nature. “Fungi are nature’s great recyclers, and they beautifully represent the interconnected cycles of decay, regeneration, and rebirth that underpin our world,” observes Dillon.

Fairy rings encourage biodiversity and keep soil chemistry balanced. 

“The importance of fungi in regulating the biogeochemical cycle, decomposing organic matter, and restoring nutrients is absolutely crucial to the environment,” Zotti affirms. His paper, “One ring to rule them all,” discusses how fairy ring fungi work as ecosystem engineers that foster plant and microbial diversity. Zotti says it’s a fascinating area to study because you can witness so many different biological phenomena, such as competition, decomposition, and entropic relationships.

“I hope in the future, more people will concentrate on studying fairy rings because it’s the perfect phenomenon to study nature and how it works,” Zotti declares. “I think everyone who wants to study soil biology or ecology should study fairy rings. It’s so exciting to put your hand in the soil.”