Agaricus arvensis

The horse mushroom, Agaricus arvensis, is a mushroom of the genus Agaricus. It is one of the largest white Agaricus species in Britain and North America. It is frequently found near stables, as well as in meadows, where it may form fairy rings. It is sometimes found associated with spruce.

The cap is similar to that of Agaricus campestris, but the gills are white at first (when this fungus is most often confused with deadly Amanita species), but later pass through grey and brown to become dull chocolate. There is a large spreading ring, white above but sometimes with yellowish scales underneath. The odor is described as like anise. It belongs to a group of Agaricus which tend to stain yellow on bruising.