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The Science (And Magic) Of Wyoming's Fairy Rings

Wally Eberhart / Getty Images
Fairy rings are formed by fungus as it spreads through grass.

Fairy rings are all around Wyoming, so it's possible you have seen them without noticing - they look like rings of extra-green grass or mushrooms. The circles can be explained by science, but, as their name suggests, are the subject of many folklore stories. How that came about starts with a story about dancing.

Sabina Magliocco is an anthropology professor at the University of British Columbia. She said dancing used to look quite different than it does today.

"At one time, circle dancing was actually the most prevalent form of folk dance all over Europe," she said. "People would dance in a circle, usually at festivals and celebrations."

Magliocco said people would dance outside of churches or their homes and not many other places. But fairies were different.

"Fairies would dance in these places out in the countryside, and they would leave this evidence that they had been there," she said.

This evidence was fairy rings, or perfect circles of green grass and mushrooms. Magliocco said fairies were a way for people to explain the unexplainable rings they were seeing.

"The word 'weird' actually is tied to the old Anglo-Saxon word that means fate or destiny," she said. "If something was weird in the old days, it was somehow connected with fate or destiny or mystery or the unknown. And fairy rings were definitely weird to our ancestors."

Magliocco said people were often afraid of fairies. It was commonly believed that fairies would punish people for breaking certain social norms. Intruding inside a fairy ring was one of them.

"Stepping inside the fairy ring, because that was fairy space, because that had been marked as fairy space, could get you into trouble," said Magliocco.

But University of Wyoming botany professor Steve Miller said it's probably ok to step inside one of the rings since it's now understood that they are created by fungus as it grows through grass.

"The ring itself is a zone where they have killed the grass and then they have kind of fertilized the next layer of grass out," he said. "So the grass that forms the fairy ring is much greener than the other grass around it."

Credit Petr Brož
Caption: Fairy rings don't have to include mushrooms. Many are just dark circles of grass.

Miller said the circles can continue to grow as long as they have a flat and moist area.

"Because it takes all of the nutrients in a certain zone around the growth of the fungus, it can only grow outward," he said. "In an area that's very, very large, they can continue to grow for a very, very long period of time."

Miller first noticed the fairy rings in Wyoming from the air. As a botanist, he said he was fascinated.

"I used to be a pilot, and I had a small airplane, so I flew all over the Laramie Basin because I loved to look at the different physiographic features: the grass and the lakes and the rivers and everything. And I was just astounded by how many fairy rings that were out there."

And it's not hard to find fairy rings on your own.

"If you go to Google Earth and you look at the westernmost runway at the Laramie Regional Airport, it looks like big olympic rings off of the end of the runway," said Miller. "Those are fairy rings. And once you see those, then you can start looking all over."

Using Google Earth and historical images, Miller and his research team measured the age and size of fairy rings in the Laramie Basin. The largest circles are 100 meters across and grow about 4 centimeters per year, meaning they've been around for a long time.

"We've traced the fairy rings over the years and created an average growth rate and from that we can back calculate how old they are," he said. "Some of the fairy rings are easily 2000 years old."

Many species of fungi form fairy rings, and in some cases, they come in contact with each other and create complicated structures.

"You end up with not necessarily full rings, but all kinds of arcs and half moons and things like that," said Miller.

Of course, not everybody loves fairy rings. They can be pesky when they show up on golf courses or yards because they're notoriously hard to get rid of. But anthropologist Magliocco said that's part of the magic.

"I think that human beings must have been fascinated by these formations, right?" she said. "I mean they are perfectly round, and they often occur seasonally. They often occur in the same areas again and again."

Miller said fairy rings are a natural part of life. Instead of getting rid of them, he said we should enjoy them and the stories they inspire.


Ashley is a PhD student in Astronomy and Physics at UW. She loves to communicate science and does so with WPM, on the Astrobites blog, and through outreach events. She was born in Colorado and got her BS in Engineering Physics at Colorado School of Mines. Ashley loves hiking and backpacking during Wyoming days and the clear starry skies at night!
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