A fairy ring, also known as a fairy court, fairy walk, fairy ground or hag track, is a dark patch of grassy ground that produces a circle, or partial circle, of small mushrooms, usually in autumn.

What causes a fairy rings?

Fairy rings are common on lawns and playing fields, and are normally caused by the fairy ring champignon Marasmius oreades. The species is quite harmless, unless you require blemish-free turf.

People once believed that fairy rings were dance floors for night- time fairies, with the mushrooms providing seats for the little folk. In fact, a fairy ring marks the outer limit of a single fungus that is hidden away in the soil for most of the year. Just like mould on jam, fungi radiate outwards in circles – the bigger the ring, the older the fungus.

The mushrooms are reproductive fruitbodies that sprout above ground when the conditions are right. They appear at the edge of the growth ring and all belong to the same organism, like apples on a tree.

The dark patch in the grass is also created by the fungus, which produces plant-suppressing chemicals as it develops. However, it also liberates nutrients in the soil, enabling the vegetation at the edge of the circle to grow taller.

Main image © Mrs skippy, Public domain, via Wikimedia Commons