Common Names: The Sidewalk Mushroom, Torq, The Firm Champignon, The Banded Agaric and the Spring Agaric.
Etymology: bitorquis is Latin for “having two collars”.
Pileus: 4-14(18)cm wide, broadly convex soon becoming plane to slightly depressed in the center. Often dirty. Glabrous with tiny appressed fibrils, very finely scaly-flaky. White or whitish, sometimes finely cracking in age, not staining yellowish, but sometimes with a dingy yellowish or slightly grayish discoloration. Margin inrolled when young and often extending beyond the gills. Dry.
Stipe: 2–5cm long, 1.5–3(4)cm thick, white to whitish, very firm,solid, smooth, partial veil white, membranous, leaving a large and distinctive double annulus with a flaring upper edge, the lower thinner one somewhat resembles a volva in very short-stemmed individuals. Equal to enlarged at the base. Often narrowed or pointed, subterraneously.
Flesh: White, not staining but may discolor faintly pink when injured. Solid and firm.
Gills: Nearly free to free, very narrow, close to crowded, very pale pink when young, becoming pinkish brown to deep blackish brown in age.
Odor: Mild to pleasant, faintly almond.
Taste: Not distinctive or slightly mushroomy.
Frequency: Somewhat rare in the Northeast.
Season: Late spring to autumn.
Spore print: Deep chocolate brown.
Microscopy: Spores subglobose to broadly elliptical, 4–6.5 × 4–5µ. smooth, apical pore absent. Nonamyloid. Basidia 4-spored, but often 2-spored. Cheliocystidia clavate, thin walled and numerous.
Habitat: Gregarious or scattered on hard-packed soil, often found along roadsides where salt is used and near barnyards. Sometimes in gardens or on compost piles. You’ll often see the ground cracking above them before the mushrooms actually appear, sometimes they are found growing right through pavement. They often fully mature while still underground.
Agaricus bitorquis is recognized by its double annuli and frequently short and stout stature as well as a strongly inrolled pileus margin. The stipe is typically very firm, this is also a key feature. Similar to the common button mushroom Agaricus bisporus and regarded as just as tasty by most who have eaten it.
Compare to Agaricus andrewii, Agaricus campestris and Agaricus arvensis