Mushroom of the Week: The Fairy Ring Mushroom


The Fairy Ring mushroom is delightfully named, evoking childhood legends of elves and fairies dancing around a ring of mushrooms.  They often grow in a circular pattern called fairy rings which were believed to be the place where dragons rested (Austria) or where the devil churned his milk (Holland) or where bisons danced (Native Americans). 

The species we are concerned with here is also known as the Scotch Bonnet, the Clover Windling (don't the British have cute little names?) and the Mousseron, but its true Latin name is Marasmius oreades. 

In the mushroom world Marasmius oreades is also referred to as an "LBM" or Little Brown Mushroom which is a term generated to deter beginners from attempting to eat any little brown mushrooms because that group includes a lot of hard to identify and poisonous species.  Best to err on the side of caution as one builds a bigger vocabulary of mushrooms that they can identify.  In all honesty though, this little brown mushroom is not too hard to learn to identify. It has a light brown cap typically with a bump or “umbo” in the center of it.  Its gills are widely spaced apart and are quite broad, or wide, for their size.  They produce white spores if you set them on dark paper overnight and their stems lack a ring, or partial veil, on them and are quite unusually tough, unlike the vast majority of other little brown mushrooms which have fragile stems. 

They also have a certain pleasant odor to them that you will come to recognize once you start noticing them.  They grow all over the place such as my lawn, Sweeney Park and probably three quarters of the lawns in town.

A fairy ring occurs when fungi produce fruiting bodies in a circular pattern.  The ring expands year after year as they digest grass or roots buried beneath the soil.  More often than not one will encounter just an arc or partial circle pattern or simply just a cluster of mushrooms.  Over 60 to 80 species can produce fairy rings if they want to and they fall into two groups: those made by saprobic fungi (decayers) are called “Free Fairy Rings” and those made by mycorrhizal fungi (symbiotic ones with trees) are called “Tethered Fairy Rings.”  Species that can produce them are numerous including our little Scotch Bonnet, Agaricus campestris (the white button mushroom), Chlorophyllum molybdites (the Sickener), and even Amanita muscaria (the Mario Brothers mushroom, my name for it). 

So, of all these species, why does the Scotch Bonnet receive the honor of often being called the Fairy Ring mushroom?  Probably because it is the most common of all of them and is a very good edible species too.

Free fairy rings are typically found in grass lawns and baseball fields.  Tethered fairy rings are typically found in woodlands circling the tree they are living with.  It is suspected that our little Clover Windling may release toxic levels of ammonia or cyanide into the soil as it digests the sugars hidden in the roots they decay there.  This may kill the grass in the area allowing fast growing plants such as weeds to take hold.  If you want to get rid of them don't try stepping on them as this will certainly not succeed.  The fungi is the mycelia living in a vast network in the soil and the mushrooms are merely fruiting bodies that one sees from time to time.  Porosity of the soil may be an issue so heavy watering might help your lawn survive if you find those pesky Windlings doing any damage.

In France it is claimed there exists a fairy ring of Mousseron that is 2,000 ft in diameter and over 700 years old.  Probably all you'll find in our town are little groups of a dozen or so or arcs comprising part of a ring.  They dry very easily for preserving and reconstitute just as easily with a remarkably pleasant flavor for making soups or sauces with. 

So, keep your eye out for those Scotch Bonnets, and imagine the dragons and fairies that may have lived here in our tiny town many centuries ago.

Gary Gilbert teaches and leads mushroom walks in the area and is a member of the Boston Mycological Club. He is the originator of “Mycocards”, flashcards for learning mushrooms by genus as well as having recipes in the recent Fantastic Fungi Community Cookbook.

fungi, fairy ring, mushroom