Common Name: Western Giant Puffball
Fruiting body 10-25 cm in height, 20-50 cm broad, compressed-globose to cushion-shaped, attached to the substrate by a cord-like rhizomorph; exoperidium up to 5.0 mm thick, surface glabrous to inconspicuously tomentose, at first whitish, then greyish-white to greyish-tan, in age developing large, flat to raised, polygonal to irregularly shaped warts with brownish centers; at maturity warts shallowly to deeply incised, falling away to reveal a pale greyish, glabrous to felty endoperidium, or dehiscing with the endoperidium exposing the underlying gleba; subgleba absent or rudimentary; gleba white, becoming yellowish-green, olive-brown, to brown, powdery in age; odor and taste not tried.
Spores 4.0-5.0 x 4.0-4.5 µm, globose to subglobose, smooth to minutely punctate, with a single oil drop, pedicel short, inconspicuous; spores olive-brown to brown in deposit. Capillitium "Calvatia type," wavy, septa common, readily fragmenting; pores frequent, very small; paracapillitium absent.
Solitary, scattered, or in fairy rings in coastal grasslands; also in montane regions in meadows, along dirt roads, forest openings, near stream drainages, and in sagebrush scrub; fruiting from mid-winter to spring in the coastal zone, late spring in the western slopes of the Sierra Nevada, and during the summer in the Eastern Sierra after thunderstorms; occasional, uncommon most years.
Presumably edible like most true puffballs when young and the gleba still white.
Calvatia booniana is California's largest puffball and the western counterpart to Calvatia gigantea, an equally large but usually smooth-skinned puffball found east of the Rocky Mountains. Besides size, distinguishing characters are a subglobose to cushion shape, broad flat to raised warts with brownish centers, and a root-like basal attachment. Although it is widely distributed in the western U.S., it is not common in California except in wet years. Calvatia booniana is sometimes confused with three medium-sized puffballs: Calbovista subsculpta, Calvatia sculpta, and Calvatia pachyderma. Calbovista subsculpta is most similar with an exoperidium of broad warts, and a rooted base, but it possesses a well developed subgleba, a feature lacking in Calvatia booniana. Microscopically the capillitium of Calbovista subsculpta is distinctive, composed of individual elements with short antler-like side branches. Calvatia sculpta is recognized by large, hooked warts and a usually well developed pseudostipe. Calvatia pachyderma differs in a nearly smooth exoperidium and fruiting body that tends to open by large vertical splits. A fourth species, Calvatia polygonia, known from Colorado, but not yet documented as occurring in California is very similar to Calvatia booniana. It is distinguished by conspicuously ornamented spores.