Western Jack-O’-Lantern

Omphalotus olivascens

This large, orange-capped mushroom glows bright green in the dark and is found on oak and eucalyptus stumps from late fall to mid-winter.

Appearance

• Cap is orange and 6-18 cm. wide
• True gills present on the underside of the cap
• Spore print is cream to pale yellow
• Stipe (stem) is central or off-center, tapering from cap, and 5-15 cm. long, 1-4 cm. thick
• Often grows in clusters

ID Tips

• May be confused with California golden chanterelle (Cantharellus californicus), which has not yet been found in Edgewood
  • Western jack-o’-lantern
    • Grows on stumps or buried roots
    • Has true gills
  • California golden chanterelle
    • Grows in soil
    • Has ridges (or false gills)

At Edgewood

• See iNaturalist for observations in Edgewood

About

• Basidiomycetes – a major lineage of fungi that usually produce spores within basidia (club-like structures)
• Found from late fall through mid-winter
• Saprotrophic – common on oaks and eucalyptuses, especially on stumps or buried roots
• Edibility (San Mateo County Parks prohibits removal of any natural material)
  • Toxic
  • Unless you are an expert, do not pick and consume wild mushrooms

Fun Facts

• This mushroom will bioluminesce in the dark, glowing bright green when fresh, and is the West Coast’s most bioluminescent mushroom

Learn More

Kuo, M. 2021, Mar. The gilled mushrooms. MushroomExpert.Com.

Michelson, M. 2015, Mar. 26. Why Mushrooms Glow. California Academy of Sciences.

Mirus, R.S. 2023, Sep. 25. Why do some mushrooms glow in the dark? The Outside Story. Center for Northern Woodlands Education.

Roehl, T. 2017, Jul. 14. #013: Characteristics of division Basidiomycota. Fungus Fact List. Fungus Fact Friday.

Roehl, T. 2017, Jul. 7. #027: Gilled mushrooms (agarics). Fungus Fact List. Fungus Fact Friday.

References

Desjardin, D.E., M.G. Wood, and F.A. Stevens. 2016. California Mushrooms: The Comprehensive Identification Guide. Timber Press, Portland, Oregon.

Kuo, M. 2023, Sep. 8. Omphalotus olivascens. MushroomExpert.Com.

Viess, D. 2024. Omphalotus olivascens. Mushroom of the Month Archive. Bay Area Mycological Society.

Wood, M., and F. Stevens. 2020. Omphalotus olivascens. The Fungi of California. MykoWeb.