Never eat a wild mushroom identified only from a website, a book or an app. Have every find checked in person by an expert, such as a mycological society.
Identification
The fairy ring champignon is a small, slender mushroom with a tan, buff or pale reddish-brown cap 2–5 cm across. It is bell-shaped when young, then flattens, usually keeping a broad central umbo. The cap is hygrophanous: it is darker when moist and dries much paler, almost cream.
The gills are widely spaced, broad, free or slightly attached, and cream to pale buff. The stem is thin, buff, and remarkably tough and elastic: it can be twisted several times without breaking, a classic field test. There is no ring. The flesh is thin and pale with a pleasant, slightly almond-like smell. The spore print is white.
A special feature is that fruit bodies dry out on the lawn and revive after rain, which is why they can appear and disappear repeatedly in the same ring.
Habitat and ecology
Marasmius oreades is a saprotroph of grassland soils. It grows in lawns, pastures, parks, road verges and dunes, almost always in rings or arcs. As the mycelium spreads outwards, it creates zones of dark green, lush grass and sometimes a ring of dead grass, a classic fairy ring.
It fruits from late spring to autumn, particularly after rain, often several times a year. It is widespread in Europe and North America and occurs on other continents.
Uses and importance
The fairy ring champignon is a well-regarded edible with a pleasant, nutty flavour. Only the caps are used, as the stems are tough. It is excellent in sauces, soups and egg dishes and dries extremely well, rehydrating quickly.
Lawn owners often see it as a problem because the rings affect the grass. It is not cultivated commercially.
Safety and edibility
The fairy ring champignon is a good edible when correctly identified and cooked, but toxic species grow in exactly the same habitat, sometimes in the same ring. Have every wild mushroom checked in person by an expert, such as a mycological society or a trained mushroom adviser, and check every single specimen.
- Clitocybe dealbata and Clitocybe rivulosa are small, whitish mushrooms of lawns and pastures that also grow in rings. They have crowded, decurrent gills and contain muscarine, which causes sweating, salivation, tears, stomach upset, slowed heart rate and breathing problems, typically within minutes to a couple of hours.
- Small brown Inocybe species, which also contain muscarine, can occur at grass edges near trees.
- Small Entoloma species in grassland have pink spores.
- Lawns may be treated with herbicides or used by pets; avoid collecting from such places.
If a mix-up is suspected, seek emergency medical help immediately, even before symptoms appear.
If you suspect mushroom poisoning, call your local emergency number or poison centre straight away, even before any symptoms appear, and keep the remains of the mushrooms.
Look-alikes
Clitocybe dealbata has a white, flat or depressed cap, crowded decurrent gills and a fragile stem; it is toxic. Inocybe species, such as the Inocybe erubescens group, have fibrous, often conical caps and brown spore prints. Collybia and Gymnopus species such as Gymnopus dryophilus have crowded gills and grow in woods. Fairy ring champignons have widely spaced gills, a tough twistable stem and a white spore print.
Around the world
Worldwide, the fairy ring champignon is one of the most widespread grassland mushrooms and is collected in Europe, North America and Asia. Fairy rings have inspired folklore in many cultures, and in some countries the mushroom is sold dried in shops.
