What’s a fairy ring of mushrooms? Why is it a circle?

Painting of circle of mushrooms with a fairy sitting on each one.
A fairy ring by Walter Jenks Morgan (1847-1924). Watercolor on paper. Image via The Victorian Web.

Note: Fairy rings are different from fairy circles in arid grassland. Read about fairy circles here..

What’s a fairy ring?

An EarthSky Facebook friend wrote:

My girlfriend and I saw this big circle of mushrooms. She said ‘Wow, a fairy ring!’ I’ve noticed this before – mushrooms growing in big circular patterns. What causes it?

The fairy ring got that name because of an old belief that fairies danced inside the circle of mushrooms.

But the real explanation isn’t nearly so fanciful. Fairy rings form as a result of the way certain types of fungi grow. Paula Flynn, a plant pathologist from Iowa State University, has written:

Although once believed to be caused by fairies dancing in a circle during the night, we now know that fairy rings are caused by an assortment of fungi that feed on dead organic matter in the turfgrass and soil. As the fungi break down this organic matter, the nutrients released may lead to a darker area of turfgrass. If the fungal structures are very dense and interfere with the movement of water to the turfgrass roots, circles of dead grass may occur. Some fairy ring fungi produce mushrooms in the circle at certain times of the year, often in late summer or early fall.

So there’s a prosaic explanation for fairy rings. But they do have a certain magic about them. Consider the ages of some of them. Scientists can measure the advance of a fungus from the increasing size of a fairy ring. Therefore, they can figure out when the ring started to grow. According to

Fruiting bodies, produced near the edge of [the ring], may widen the ring for hundreds of years.

The 2024 lunar calendars are here! Best Christmas gifts in the universe! Check ’em out here.

Large white mushrooms growing in a nearly complete circle in a lawn of mowed green grass.
A large fairy ring in Germany. Image via unukorno/ Flickr (CC BY-SA 2.0 DEED).

Why are they circles?

A fairy ring might start growing underground from a single spore. The spore sprouts a tangle of tube-like threads, which spread out horizontally in all directions, like spokes radiating from the hub of a wheel.

That’s what gives rise to the circular pattern. The part of the fungus you see – the circle of mushrooms – springs up at the edge of the circle.

Have you seen a fairy ring? Share your photo!

Irregular circle of white mushrooms growing in short green grass.
A fairy ring at Schloss Charlottenburg. Image via Olivier Bruchez/ openverse (CC BY-SA 2.0).

The fungus might kill off grass

You can sometimes see rings of mushrooms as dark green circles surrounding patches of dead grass. That’s because, as the fungus grows, it gradually decomposes the grass in its path. The dark green color of the fairy ring arises from the release of phosphorus and nitrogen from the most recently decomposed grass.

So should you try to remove a fairy ring if you see one in your yard, so that it doesn’t kill your grass? Paula Flynn at Iowa State wrote:

Fairy rings are difficult to eradicate from an area. Fungicide products are not usually very effective, which leaves removal of the soil in the affected area the primary means of control.

This may not be feasible if the fairy ring has a large diameter.

And that’s why, Flynn said:

A mycologist (fungal expert) would likely recommend treating a fairy ring as an interesting curiosity rather than a problem.

A wooded area with a thick circle of mushrooms around a tree.
A fairy ring of Clitocybe nebularis (aka Clouded Agaric or Clouded Funnel) Image via Josimda/ Wikimedia Commons (CC BY-SA 3.0).

Bottom line: Mushrooms growing in a circle are known as a fairy ring. They begin as a single spore that sprouts a tangle of tube-like threads, which spread out horizontally in all directions.

Enjoying EarthSky? Sign up for our free daily newsletter today!

October 24, 2023

Like what you read?
Subscribe and receive daily news delivered to your inbox.

Your email address will only be used for EarthSky content. Privacy Policy
Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.

More from 

Deborah Byrd

View All