Jumbo Gym (Gymnopilus ventricosus)

🏷️ Description

If you ever stumble upon a massive, golden-orange mushroom with a thick stem and dinner plate-sized cap growing on decaying wood, you might have found Gymnopilus ventricosus, also known as the jumbo gym! This striking member of the Hymenogastraceae family is a true spectacle in the fungal world.

🌱 Origins & Classification Originally described in 1902 by mycologist Franklin Sumner Earle, Gymnopilus ventricosus was first classified as Pholiota ventricosa before being reassigned to its current genus. For years, it was confused with Gymnopilus spectabilis (now Gymnopilus junonius), but recent research suggests G. ventricosus is a distinct species found primarily in North America, especially along the West Coast.

🔎 Identification

• Cap: 5-30 cm (2-11+ inches) wide, yellow-orange to rusty orange, convex at first, then flattening with age. The surface has fine brown scales.

• Gills: Attached to the stem (adnate to adnexed), initially yellow, turning orange with age.

• Stipe (Stem): Thick, bulbous, and club-shaped, 7-21 cm (3-8 inches) long, with a membranous ring that often collects spores.

• Spores: Elliptical, roughened, measuring 7.5-10 x 4.5-6 µm, with a rusty-orange spore print.

• Odor & Taste: Smells mild to pungent, but the taste is extremely bitter!

🌲 Habitat & Growth

Gymnopilus ventricosus is saprotrophic, meaning it feeds on decaying wood. It prefers rotting logs, stumps, and snags of both hardwoods and conifers. You’ll typically find it in dense clusters from early fall to mid-winter.

🥦 Edibility & Psychoactivity

Despite its impressive appearance, Gymnopilus ventricosus is inedible due to its overwhelming bitterness. Unlike its close relative, G. junonius (also called the Big Laughing Gym), G. ventricosus does not contain psilocybin and has no known hallucinogenic effects.

👀 Look-Alikes

• Gymnopilus junonius: Smaller, thinner stipe, and potentially hallucinogenic in some regions.

• Large Pholiota species: Have a similar clustered growth habit, but lack the bright orange hues and rusty spores of Gymnopilus.

Uses

Though inedible, dried Gymnopilus ventricosus can be used as a natural dye, producing shades ranging from light brown to dark brown depending on the mordant used. This makes it a valuable resource for fiber artists and natural dye enthusiasts.

Photo sources:

Photo 1 - Author: John Hibbard (CC BY 4.0)

Photo 2 - Author: Nelson Balcar (CC BY 4.0)

Photo 3 - Author: Irina Mitine (CC BY 4.0)

Photo 4 - Author: Cricket Raspet (CC BY 4.0)