Cap 6-18 cm broad, convex, broadly convex at maturity; margin incurved at first, expanding and becoming wavy, upturned in age; surface smooth, moist, dull orange to orange-brown, developing olive tones; flesh thin, pliant, same color as cap; odor and taste mild.
Gills decurrent, concolorous with cap or lighter, luminescent; veil absent.
Stipe 5-15 cm long, 1-4 cm thick, central to off-central, tapering downward, smooth, yellowish-olive, with brown stains at the base.
Spores 6.5-8 x 6-6.5 µm, globose to ovoid, smooth, nonamyloid. Spore print cream to pale yellow.
Clustered at the base of hardwood stumps or from buried roots; most common with oaks and Eucalyptus. Fruits from late fall through mid-winter.
Toxic; causes severe gastrointestinal upsets.
The Jack O'Lantern fungus is sometimes also called a False Chanterelle because of its yellowish color and decurrent gills. It can, however, be distinguished from the true chanterelle, Cantharellus cibarius, by a combination of characters: Cantharellus cibarius has ridges rather than true gills, never develops the olive tones of the Jack O'Lantern, and grows in oak duff, not on rotting wood. Omphalotus olivascens is interesting in that the fruiting bodies are luminescent, at least when fresh, though to appreciate this quality requires sitting for many minutes in a completely dark room before the greenish glow becomes visible. In fresh specimens this glow is sometimes bright enough to read a newspaper!