Gasteroid Agaricus

The fruit body can grow up to 5 to 18 cm (2 to 7 in) in height. Fresh specimens are usually white, but will age to a pale tan; dried fruit bodies are light gray or tan mixed with some yellow. The cap is 4 to 10 cm (1.5 to 4 in) in diameter, initially conic, later becoming convex to broadly convex as it matures. The cap is composed of three distinct tissue layers: an outer volval layer, a middle cuticular layer (cutis), and an inner (tramal) layer which supports the gleba. The surface of the cap is white with yellow-brown to brown-tipped raised small scales; these scales result from the breakup of the volva and the cutis. Initially, the caps are covered by a peridium—an outer covering layer of tissue. After the fruit body matures and begins to dry out, the lower part of the peridium starts to rip, usually starting from small longitudinal slits near where the peridium attaches to the top of the stem. However, the pattern of tearing is variable; in some instances, the slits may appear higher up on the peridium, in others, the peridium rips more irregularly. The peridium may also rip in such a way that it appears as if there is a ring at the top of the stem. The torn peridium exposes the internal gleba. The gleba is divided into wavy plates or lamellae, some of which are fused together to form irregular chambers. …

Like other Agaricus species, A. deserticola is saprobic—feeding off dead or decaying organic matter. The fruit bodies are found growing singly to sometimes more numerous, at low elevations, and typically in sandy soil. The species' usual habitats include drylands, coastal sage scrub, and desert ecosystems. It also grows in lawns and fields. The range of the fungus is restricted to southwestern and western North America, where it fruits throughout the year, typically during or following cold, wet weather. Zeller gives a range that includes as its eastern border central Texas, and extends westward to San Diego County, California, and north to Josephine County, Oregon. The mushroom used to be common in the San Francisco Bay area before land development reduced its preferred habitats. A. deserticola has been collected in several states in northwestern Mexico, including Sonora, Chihuahua, and Baja California.

The edibility of A. deserticola fruit bodies is not known definitively, and there are conflicting opinions in the literature, with some sources claiming that the edibility is unknown and consumption should be avoided. However, one popular field guide to North American mushrooms suggests they are edible when they are young and have a pleasant odor and mild taste.