The work of fairies!

November 2023

On Friday 17 November, Gloucester the Dog, pictured above, hijacked our social media accounts and asked our followers to identify the mystical cluster of mushrooms he found on his walk.   In response to those who followed the thread, we solve the mystery below and it has nothing to do with dancing fairies!

Fairy Rings on Banstead Commons

Many different mushrooms form so-called fairy rings. Some of these rough circles can be made out throughout the year when they are in open grassland, a bit like the crop marks that can betray the presence of underground archaeology.

The cause of the marks is the variation in nutrients available to the grass growing on the surface. When the mushrooms are present, it is obvious what causes the visible ring in the grass but, without them, people wondered if the difference between the bright green inner edge and the browner outer edge was caused by fairies dancing around in a circle in the night and trampling a ring of grass.

What actually happens is that a single fungus grows underground.  The individual fungal mycelium, a network of fungal threads or hyphae, advances underground in an ever-expanding circle.  Fruiting is triggered by climatic conditions and, when the conditions are right, a ring of mushrooms, the fruiting bodies of the mycelium, can be found above the ground like in the pictures below. Some of these rings expand at a rate of six to eighteen inches a year.

The biggest recorded is 2km across so that meadow has been undisturbed for rather a long time!

The difference in colour in the grass scientists believe is a result of the fungal hyphae collecting nutrients from the grass and releasing nitrogen that promotes lush growth in the grass.

The most common mushroom with this habit is actually called the Fairy Ring Champignon (Marasmius oreades) and they can be found widely on Banstead Commons. But several other mushrooms grow in rings not only in the grass but also in the woods (where they are only visible when the mushrooms’ fruiting bodies are present).


Image: Fairy Ring on Banstead Heath

Article written by Conservator, David Hatcher

Photographs:  Gloucester the dog sitting in the middle of a Fairy Ring on Banstead Downs (John Buckland) and the Fairy Ring on Banstead Heath (Ian Mockford)