I had no idea that phosphorescent fungi existed, and suspected the photographer, Damon Tighe, of photoshopping the glow onto this image, but it turns out the photo is legitimate. Once again I am astounded at the diversity of the botanical world (sorry to have doubted you, Damon!).
Omphalotus olivascens, or the Western jack-o-lantern fungus, earns its common name from the phosphorescent enzyme that is secreted from its gills. This enzyme makes the fruiting fungus glow in the dark. The fruiting period coincides with Hallowe’en, but the Western jack-o-lantern is all trick and no treat. The mushroom smells delicious, and looks quite similar to a chanterelle (Cantherellus spp.), but when ingested will result in multiple days of diarrhea and vomiting–a tummy ache worse even than the one my 5 year-old had the year that he decided to eat most of his Hallowe’en treats in one sitting.
Although Omphalotus olivascens is found abundantly in north-central California, I could not find information about its exact entire range. It is often described as a western North American species, and on the east coast of North America the very similar Omphalotus olearius can be found. The western species of jack-o-lantern fungus has a brownish-orange to olive coloured cap and large spores, while the eastern species is bright orange and has smaller spores. Botany Photo of the Day published a great write-up about the eastern Omphalotus olearius in 2009, which explains in more detail the phenomenon of phosphorescence found in both of these species of Omphalotus.
Moselio and Elio Schaechter, in In the Company of Mushrooms: A Biologist’s Tale, shed more light (haha) on the topic of fungal phosphorescence. According to the Schaechters, the greenish glow emitted by Omphalotus species is called “foxfire”, and is found not only on the mushroom’s gills, but also in the fungus’ mycelium. Rotting wood full of such mycelium can be seen to glow for a couple of weeks, and this “touchwood” has a rich cultural history. The Schaechters describe it as having been used by native American shamans, lost Scandinavians, World War 1 soldiers, and maybe even Moses, for lighting and night-time wayfinding.