Omphalotus olivascens – The Western Jack O’Lantern Mushroom

]Omphalotus olivascens - Western Jack O'Lantern Mushroom
Omphalotus olivascens growing from the base of an interior live oak (Quercus wislizeni).

Over the past few weeks, I’ve been finding lots of Omphalotus olivascens, the “Western Jack O’Lantern Mushroom,” fruiting on interior live oak (Quercus wislizeni) in Placer County. This is a saprobic species that feeds on rotting or decaying hardwoods, especially oaks.

Omphalotus olivascens - Western Jack O'Lantern Mushroom
Detail of O. olivascens gills, showing subtle olive/violet tones.

This mushroom species is really charismatic, and is one of my favorites. To start, its gills bioluminesce. The bioluminescent effect is subtle, and I’ve only photographed it once. I had to expose this mushroom for 30 seconds at f/3.5 and ISO 3200 in order to show the glowing green bioluminescence.

Bioluminescent Western Jack-O'-Lantern Mushroom
Bioluminescing O. olivascens.

The bioluminescence of this species and its neighbor east of the Rocky Mountains, O. illudens, is undeniably cool. Michael Kuo’s frustrated descriptions of trying to get O. illudens to glow are very amusing and well worth reading. I haven’t been able to see the green glow with my naked eyes yet, but it wasn’t too hard to photograph.

Omphalotus olivascens spore prints
This fungus creates a pale-yellow sporeprint. I sporeprint directly on glass slides to facilitate microscopy.

Mykoweb states that the spores are “6.5-8 x 6-6.5 µm, globose to ovoid, smooth, nonamyloid. Spore print cream to pale yellow.” I’m still nailing down my microscopy technique, but the spores I measured were mostly globose and averaged 6.1 µm.

Omphalotus olivascens spores
Afocal photograph of O. olivascens spores with an iPhone. Measurement via Piximetre software.

This toxic species is sometimes mistaken for edible Chanterelles (Cantharellus sp.), but they’re easily differentiated by their true gills and olive tones. Despite its toxicity, O. olivascens has a fantastic use. It’s a remarkable dyeing mushroom, capable of producing a variety of tones, from gold to purple, depending on the dyeing methodology used.

All Photos-31
O. olivascens drying in my food dehydrator, to be used in wool-dying experiments.

I first learned of the dyeing-properties of mushrooms via Alissa Allen of Mycopigments, and Dustin’s writing and photographs of dyeing with Omphalotus on her blog are wonderful. I’m just starting to learn how to dye and work with fibers, and will write more later. I’ve been using The Rainbow Beneath My Feet: A Mushroom Dyer’s Field Guide, and working with the fine folks at the Mushroom Dyer’s Trading Post to learn more about fungal-based dyes.

Omphalotus olivascens – The Western Jack O’Lantern Mushroom

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