Why do some mushrooms grow in a circle, forming a 'fairy ring'?

QUESTION:

As a kid, I remember seeing rings of mushrooms on my parents’ lawn. It’s been a very long time since I saw that. Recently I took my own kids to a local park and saw a fresh new ring. It brought back a lot of memories.

But when my youngest asked me what it was, and why the mushrooms grew in a ring, I realized I didn’t know.

Please enlighten me!


ANSWER:

The sight of mushrooms growing in a circle, often called a "fairy ring," has intrigued people for centuries and is surrounded by various myths and folklore. However, the scientific explanation is equally fascinating.

A fairy ring forms when a mushroom's mycelium, the network of fungal threads that live underground, spreads outwards in a circular pattern. The mycelium grows from a central point, consuming nutrients in the soil as it expands. Once the mycelium has used up the nutrients in the center, it begins to die off there, but the outer edges continue to grow, forming a ring.

When the conditions are right, such as sufficient moisture and the right temperature, the mycelium will produce fruiting bodies (the mushrooms) at the outer edge of the circle. Over time, this process can result in a ring of mushrooms, sometimes several feet across. The ring often appears year after year, slowly expanding as the mycelium continues to grow outward.

Fairy rings can be found in various habitats, including lawns, meadows, and forests. Some species commonly associated with fairy rings include Marasmius oreades (the Scotch bonnet) and Agaricus campestris (the meadow mushroom).

In folklore, these rings were often associated with supernatural activity, such as fairies dancing in the circle, hence the name "fairy ring." People in the past sometimes believed that stepping inside a fairy ring could lead to being trapped in the fairy world or bring bad luck.

Today, while the mythological aspects are less believed, the sight of a fairy ring still captures the imagination and is a reminder of the mysterious and interconnected world of fungi beneath our feet.

Great question and I hope you enjoyed the answer!

Best wishes,

Nick