almond mushroom

The cap is initially hemispherical, later becoming convex, with a diameter of 5 to 25 centimetres (2 to 10 inches). The color of the cap may range from white to grayish or dull reddish brown; it stains yellow in KOH. Its surface is covered with silk-like fibers, although in maturity it develops small scales (squamulose). The cap margin typically splits with age. The flesh is white, and has the taste of "green nuts", with the odor of almonds. The gills are not attached to the stalk (free), narrow, and crowded closely together. They start out whitish in color, then later pinkish, and finally black-brown as the spores mature. The spore print is brown. The spores are ellipsoid, smooth, dark purplish-brown when viewed microscopically, with dimensions of 5.5–7 by 4–5 μm. The stipe is 6 to 15 cm (2+1⁄2 to 6 in) long and 1 to 4 cm (1⁄2 to 1+1⁄2 in) thick, and sometimes bulbous at the base. Initially solid, the stipe becomes hollow with age; it is cottony (floccose) to scaly toward the base. The annulus is abundant and double-layered; it is bent downward toward the stem, smooth and whitish on the upper side, and covered with cottony scales on the lower side. A type of ergostane-type compounds called blazeispirols have been isolated from A. subrufescens.

A. subrufescens forms fruit bodies singly or in clusters in leaf litter in rich soil, often in domestic habitats. Originally described from the northeastern U.S. and Canada, it has been found growing in California, Hawaii, Great Britain, the Netherlands, Taiwan, Japan, Philippines, Iran, Australia, Brazil, and Uruguay.

The mushroom is edible for most people, with a somewhat sweet almond-like aroma and flavor resulting from benzaldehyde, benzyl alcohol, benzonitrile, and methyl benzoate. Used in traditional and alternative medicine for supposed anti-cancer effects, Agaricus mushrooms have not been assessed by sufficient high-quality clinical research to define safety and biological properties upon consumption as a food, dietary supplement, or drug.