What Causes Fairy Rings?

Fairy rings are circles (sometimes arcs or incomplete circles) of mushrooms or brown grass that appear in lawns. The name comes from folktales about fairies dancing around in a circle to cause the ring in the lawn.

A fairy ring of mushrooms. Image via Wikimedia Commons.

Scientifically, fairy rings indicate the precesnce of a mycelium, which is the threadlike, vegetative portion of a fungus that is typically belowground. There are many different kinds of fungi that can cause a fairy ring, but no one knows exactly how they become established. In some fairy rings, the mycelium prevents water from penetrating the soil, effectively killing the grass and forming a brown circle. Proper lawn care can prevent or help cure such fungal infections. Other fairy rings are harmless to your lawn and only produce mushrooms as a cosmetic issue. However, they can still indicate excessive moisture that can invite harmful fungi to your yard as well.

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