# Fairy ring champignon (Marasmius oreades)

**Marasmius oreades**

**Known today as.** A small tan mushroom that grows in rings on lawns and pasture.

Kind: Fungus

## What was it used for?

A choice edible, which revives when wetted after drying.

## What does modern science say?

The ring is the living edge of the fungus’s mycelium, spreading outward through the soil as the centre dies.

## Pharmacognosy and toxicology

- **trehalose**: which lets it revive after drying
- **a cyanide-like odour**: in the gills

**Mechanism.** A choice edible whose trehalose lets it survive drying and revive when wetted. The hazard is its ring-forming lookalike, the fool’s funnel (*Clitocybe*, now *Collybia*, *rivulosa*), whose main toxin is muscarine.

**Dose.** A food.

**Standing.** A food; deaths from the lookalike are rare but possible.

## What lore surrounds it?

The rings in the grass were where fairies or elves danced, or, in German tradition, where witches danced on Walpurgis Night; in the Netherlands they were where the Devil set down his milk churn. To step inside one was to risk being held there by the fairies, made to dance to exhaustion, or kept for years.

## Sources

- Wikipedia contributors. “Marasmius oreades.” *Wikipedia, The Free Encyclopedia*. en.wikipedia.org/wiki/Marasmius_oreades (read 2 October 2026).
- Wikipedia contributors. “Fairy ring.” *Wikipedia, The Free Encyclopedia*. en.wikipedia.org/wiki/Fairy_ring (read 2 October 2026).
- Wikipedia contributors. “Clitocybe rivulosa.” *Wikipedia, The Free Encyclopedia*. en.wikipedia.org/wiki/Clitocybe_rivulosa (read 2 October 2026).

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*Fairy ring champignon.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-10-03. The Thinking Press. https://thethinkingpress.org/materia-medica/fairy-ring-champignon

Historical description, not medical advice.