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Omphalotus olivascens

by Michael Kuo, 8 September 2023

California's version of the "Jack O'Lantern mushroom," Omphalotus olivascens, passed as Omphalotus olearius or Omphalotus illudens until 1976, when Bigelow, Miller & Thiers named it as a separate species based on its duller orange colors, its "olive overtones or stains," the fact that dried specimens are darker, its slightly larger spores, the encrusted elements in its pileipellis, and differences in features of cultured mycelium. In the years since, Omphalotus olivascens has been supported as a biological species (Petersen & Hughes 1998) and a phylogenetic species (Kirchmair et al. 2004).

Thanks to Mila Visser 't Hooft for documenting, collecting, and preserving Omphalotus olivascens for study; her collection is deposited in The Herbarium of Michael Kuo.


Ecology: Saprobic; growing in large clusters on the stumps or buried roots of hardwoods, especially oaks; winter; originally described from California (Bigelow et al. 1976); reported from California and Baja California. The illustrated and described collections are from California.

Cap: 5–20 or more cm across; at first convex, becoming flat or shallowly vase-shaped; bald; dry; dull brownish orange, often with olive discolorations; becoming orangish brown to olive brown or brown with age; the margin incurved when young.

Gills: Running down the stem; close; yellowish olive when young, becoming yellow to orange; short-gills frequent; luminescent when fresh.

Stem: 5–15 cm long; 1–3 cm thick; tapering to base; solid; bald; yellowish, often with olive stains.

Flesh: Pale orange to pale olive; unchanging when sliced.

Odor: Not distinctive.

Spore Print: White.

Microscopic Features: Spores 5.5–7.5 x 4.5–6 µm; broadly ellipsoid or subglobose; smooth; yellowish in KOH; inamyloid. Basidia 35–38 x 4–6 µm; clavate; 4-sterigmate. Cystidia not found. Pileipellis a cutis; elements 5–7.5 µm wide, smooth or slightly roughened, hyaline to golden in KOH.

REFERENCES: H. E. Bigelow & O. K. Miller, Jr., 1976. (Smith, 1975; Bigelow et al., 1976; Smith, Smith & Weber, 1979; Arora, 1986; Petersen & Hughes, 1998; Kirchmair et al., 2004; Desjardin, Wood & Stevens, 2015; Siegel & Schwarz, 2016.) Herb. Kuo 01132101.

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Omphalotus olivascens

Omphalotus olivascens

Omphalotus olivascens

Omphalotus olivascens

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Kuo, M. (2023, September). Omphalotus olivascens. Retrieved from the MushroomExpert.Com Web site: