Marasmius oreades

Marasmius oreades
Conservation status
Secure  (NatureServe) [1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Fungi
Division:	Basidiomycota
Class:	Agaricomycetes
Order:	Agaricales
Family:	Marasmiaceae
Genus:	Marasmius
Species:	M. oreades
Binomial name
Marasmius oreades (Bolton) Fr (1836)

Marasmius oreades Mycological characteristics
	Gills on hymenium
	Cap is convex or umbonate
	Hymenium is adnexed
	Stipe is bare
	Spore print is white
	Ecology is saprotrophic
	Edibility is choice

Marasmius oreades, also known as the fairy ring mushroom, fairy ring champignon or Scotch bonnet, is a mushroom native to North America and Europe. Its common names can cause confusion, as many other mushrooms grow in fairy rings, such as the edible Agaricus campestris and the poisonous Chlorophyllum molybdites . It also resembles some toxic species, but is itself a choice edible mushroom.

Description

The cap is 1–5 centimetres (1⁄2–2 inches) across; ^[2] it is bell-shaped with a somewhat inrolled margin at first, becoming broadly convex with an even or uplifted margin. It usually retaining a slight central bump and is dry, smooth, pale tan or buff (occasionally white), or reddish tan; it usually changes color markedly as it dries out; the margin is sometimes faintly lined. ^[3]

The bare, pallid, and tough stem ^[4] grows up to about 2–6 cm (1–2+1⁄2 in) tall and 2–6 mm (1⁄16–1⁄4 in) in diameter. ^[5]

The gills are attached to the stem or free from it, ^[3] fairly thick and spaced apart, and white or pale tan, with a cyanide-like odor ^[4] and producing a white spore print. ^[6] The spores measure 7–10  μm × 4–6 μm; they are smooth, elliptical, and inamyloid. Cystidia are absent. The pileipellis is without broom cells. ^[3]

Underside

Similar species

It can resemble M. nigrodiscus . ^[6]

This mushroom can be mistaken for the toxic Clitocybe dealbata or C. rivulosa , which have closely spaced decurrent gills. ^[5] The latter lacks an umbo and is white to grey in color.

Some species of the Collybia , Marasmiellus , Micromphale , and Strobilurus genera are also similar, sometimes requiring microscopic analysis to differentiate. ^[4]

Distribution and habitat

Marasmius oreades grows extensively throughout North America, especially the east where they are also more diverse, ^[4] and Europe in the summer and autumn (May–November in the UK), ^[7] or year-round in warmer climates. It appears in grassy areas such as lawns, ^[4] meadows, and even dunes in coastal areas.

It grows gregariously in troops, arcs, or rings (type II, which causes the grass to grow and become greener).^{[ citation needed ]}

Edibility

A dried string of 50 fairy ring caps

Aside from its similarity to toxic species, M. oreades is a choice edible mushroom. ^[8] Mycologist David Arora calls it "one of the few [ little brown mushrooms] worth learning". ^[9] The mushroom reportedly has a firm, chewy texture and a meaty, spicy flavor. The mushrooms can be stored dry. ^[10]

Traditionally, the stems (which tend to be fibrous and unappetizing) are cut off and the caps are threaded and dried in strings. While used in foods such as soups and stews, its sweet taste lends it to baked goods such as cookies. The sweet taste may be due to the presence of trehalose, a type of sugar that allows the mushroom to resist death by desiccation. ^{[11] [ better source needed ]} When exposed to water after being completely dried out, the trehalose is digested as the cells completely revive, causing cellular processes, including the creation of new spores, to begin again.

References

1. NatureServe. "Marasmius oreades". NatureServe Explorer. Arlington, Virginia. Retrieved 2 May 2025.
2. Sisson, Liv; Vigus, Paula (2023). Fungi of Aotearoa: a curious forager's field guide. Auckland, New Zealand: Penguin Books. p. 122. ISBN   978-1-76104-787-9. OCLC   1372569849.
3. Marasmius oreades (MushroomExpert.com)
4. Trudell, Steve; Ammirati, Joe (2009). Mushrooms of the Pacific Northwest. Timber Press Field Guides. Portland, OR: Timber Press. pp. 113–114. ISBN   978-0-88192-935-5.
5. Davis, R. Michael; Sommer, Robert; Menge, John A. (2012). Field Guide to Mushrooms of Western North America. Berkeley: University of California Press. pp. 27, 188–189. ISBN   978-0-520-95360-4. OCLC   797915861.
6. Audubon (2023). Mushrooms of North America. Knopf. p. 458. ISBN   978-0-593-31998-7.
7. Francis-Baker, Tiffany (2021). Concise Foraging Guide. The Wildlife Trusts. London: Bloomsbury. p. 141. ISBN   978-1-4729-8474-6.
8. Miller Jr., Orson K.; Miller, Hope H. (2006). North American Mushrooms: A Field Guide to Edible and Inedible Fungi. Guilford, CN: FalconGuide. p. 196. ISBN   978-0-7627-3109-1.
9. Arora, David (1986) [1979]. Mushrooms Demystified: A Comprehensive Guide to the Fleshy Fungi (2nd ed.). Berkeley, CA: Ten Speed Press. pp. 208–209. ISBN   978-0-89815-170-1.
10. Russell, Bill (2006). Field Guide to Wild Mushrooms of Pennsylvania and the Mid-Atlantic. University Park, PA: Pennsylvania State University Press. p. 37. ISBN   0-271-02891-2. OCLC   64510388.
11. Marasmius oreades, the fairy ring mushroom, leprechaun. Tom Volk's Fungus of the Month for March 2003

External links

• Media related to Marasmius oreades at Wikimedia Commons