Western Jumbo Gym

The cap is 5 to 30 cm (2 to 11+3⁄4 in) or larger in diameter, bright yellow-orange to rusty orange, covered with minute yellow hairs, sometimes becoming scaly. The flesh is thick, yellow and bitter. The gills are yellow to rusty orange, close, adnate to slightly decurrent. The stipe is 7-21 cm long, 1-4 cm thick, yellow-orange, streaked with brown fibrils, club-shaped or ventricose, usually narrowed at the base; partial veil yellowish, forming a superior membranous ring. White mycelium at the base of the stipe. Spores are ellipsoid or ovoid, warty, 7.5–9 x 4–5.5μm. The spore print is rusty brown to rusty orange. Clamp connections are present. This species contains no psilocybin, and is considered inedible; it is very bitter.

Gymnopilus ventricosus grows in groups or dense tufts on dead wood or living pines, also on conifers and hardwoods.