|gills on hymenium|
|cap is convex|
|hymenium is free|
|stipe has a ring|
|spore print is brown to blackish-brown|
|ecology is saprotrophic|
The cap is 7–20 cm (2.8–7.9 in), whitish, smooth, and dry; it stains yellow, particularly when young. The gills are pale pink to white at first, later passing through grey and brown to become dull chocolate. There is a large spreading ring, white above but sometimes with yellowish scales underneath. Viewed from below, on a closed-cap specimen, the twin-layered ring has a well-developed 'cogwheel' pattern around the stipe. This is the lower part of the double ring. The stalk is 5–12 cm (2.0–4.7 in) long and 1–3 cm wide. The spores are brown and smooth. The odor is described as like anise. It belongs to a group of Agaricus which tend to stain yellow on bruising.
When young, this fungus is often confused with species of the deadly genus Amanita.
- Agaricus osecanus is rare, and is without the aniseed smell.
- Agaricus xanthodermus, the yellow stainer, can cause stomach upsets.
- Agaricus silvicola, the wood mushroom, is a touch more arboreal, with a frail and delicate ring, but also edible.
- Agaricus campestris, the field mushroom, is generally (but not always) smaller, has pink gills when young, and is also edible.
- Agaricus bitorquis, the spring agaricus, looks similar to arvensis and campestris, which are more common in the summer and autumn.
- Agaricus bisporus is the most commonly cultivated mushroom of the genus Agaricus.
Distribution and habitat
It is one of the largest white Agaricus species in Britain (where it appears during the months of July–November), West Asia (Iran) and North America. Frequently found near stables, as well as in meadows, it may form fairy rings. The mushroom is often found growing with nettles (a plant that also likes nutrient-rich soil). It is sometimes found associated with spruce.
This mushroom is considered common and widespread, and is not a conservation concern.
This is a choice edible species which has been much prized by farmers for generations, being regarded as one of the most delicious of all edible fungi. Despite this, the fruitbodies of this and other yellow-staining Agaricus species often have a build-up of heavy metals, such as cadmium and copper.
- Davis, R. Michael; Sommer, Robert; Menge, John A. (2012). Field Guide to Mushrooms of Western North America. Berkeley: University of California Press. p. 220. ISBN 978-0-520-95360-4. OCLC 797915861.
- Miller, Orson. Mushrooms of North America. New York: E.P. Dutton, 1984.
- Roger Phillips (2006). Mushrooms. Pan MacMillan. ISBN 0-330-44237-6.
- Asef Shayan MR. (2010). قارچهای سمی ایران (Qarch-ha-ye Sammi-ye Iran) [Poisonous mushrooms of Iran] (in Persian). Iran shenasi. p. 214. ISBN 978-964-2725-29-8.
- Lincoff, Gary. The Audubon Society Field Guide to North American Mushrooms. Chanticleer Press: New York, 1981.
- "Plants & Fungi: Agaricus arvensis (horse mushroom) - Species profile from". Kew. Archived from the original on 2013-03-18. Retrieved 2013-05-19.
- Miller Jr., Orson K.; Miller, Hope H. (2006). North American Mushrooms: A Field Guide to Edible and Inedible Fungi. Guilford, CN: FalconGuide. p. 280. ISBN 978-0-7627-3109-1.
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