|gills on hymenium|
|cap is convex|
|hymenium is free|
|stipe has a ring|
|spore print is brown to blackish-brown|
|ecology is saprotrophic|
Described as Agaricus arvensis by Jacob Christian Schaeffer in 1762, and given numerous binomial descriptions since. Its present name arvensis means 'of the field'.
The cap is similar to that of Agaricus campestris (The Field Mushroom). The gills are white at first (when this fungus is most often confused with deadly Amanita genus). They later pass 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 odor is described as like anise. It belongs to a group of Agaricus which tend to stain yellow on bruising.
- Agaricus osecanus. Which is rare, and is without the aniseed smell.
- Agaricus xanthodermus. (The Yellow Stainer), which can cause stomach upsets.
- Agaricus silvicola. (The Wood Mushroom), which is a touch more arboreal, with a frail and delicate ring, but also edible.
- Agaricus campestris, (The Field Mushroom), which is generally (but not always) smaller, has pink gills when young, and is also edible.
Distribution and Habitat
It is one of the largest white Agaricus species in Britain and North America. Frequently found near stables, as well as in meadows, where 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.
Much prized by farmers and gypsies for generations, the 'Horse Mushroom' is one of the most delicious edible fungi.
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