Why do some mushrooms glow in the dark?

Some mushrooms produce light through a reaction between a luciferin and a luciferase, two molecules they make themselves. The reaction consumes oxygen and releases energy as cold light, without heat. In the jack-o'-lantern mushroom, the glow is emitted by the gills and stays visible to the naked eye in total darkness.

Phenomenon biologytoxicology

Fungal Bioluminescence

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During an evening of ghost stories, one tale describes a will-o’-the-wisp glimpsed at the edge of a forest by terrified villagers. Maomao, unimpressed, quickly identifies the source: a basket of mushrooms carried at night, whose diffuse glow was enough to fuel the legend. She names the culprit, the jack-o’-lantern mushroom, and explains that it is often confused with the chanterelle, a highly sought-after edible mushroom. Its luminescence, far from being a harmless quirk, signals severe toxicity. The scene closes on a clear-eyed conclusion: the will-o’-the-wisp superstition had no basis beyond a misidentified mushroom in the dark.

The subject in depth

Bioluminescence refers to the production of light by a living organism through a biochemical reaction ^[Wikipedia]. The general principle rests on the oxidation of a molecule called luciferin by an enzyme, luciferase. The energy released by this reaction is not dissipated as heat but emitted directly as visible photons: this is called cold light, which distinguishes bioluminescence from simple incandescence.

Gills of the jack-o'-lantern mushroom emitting a green glow in the dark — The jack-o’-lantern’s cold light

In fungi, the mechanism was long poorly understood. Recent research has shown that fungal luciferin is a derivative of hispidin, a phenolic compound distinct from the luciferins known in fireflies or jellyfish. About eighty species of fungi are now recognized as bioluminescent, found across the globe.

The jack-o’-lantern mushroom (Omphalotus olearius) is the best-documented European species ^[Wikipedia]. Its greenish-blue glow is emitted by the gills beneath the cap. It is only perceptible to the naked eye in complete darkness and on fresh specimens: in daylight or once dried, nothing gives away this trait. The mushroom grows at the base of olive trees, oaks, and other broadleaf trees, often in clusters, from late summer through autumn.

Confusion with the chanterelle (Cantharellus cibarius) causes nearly all poisonings from the jack-o’-lantern mushroom. The two mushrooms share misleading traits: an orange to tawny color, an irregular cap, a forest habitat, and an overlapping picking season. Yet they can clearly be told apart on close inspection. The chanterelle shows thick, forked, anastomosing ridges under the cap, whereas the jack-o’-lantern mushroom has true gills, narrow, crowded, and decurrent, a vivid yellow-orange ^[Web]. The smell also differs: pleasantly fruity for the chanterelle, sharp and strong for its lookalike.

The toxicity of the jack-o’-lantern mushroom comes from compounds called omphalotins, recently characterized cyclic peptides. Poisoning causes intense gastrointestinal symptoms: nausea, repeated vomiting, diarrhea, abdominal cramps. Symptoms begin thirty minutes to three hours after ingestion and persist for several hours, sometimes a full day. The outcome is rarely fatal for a healthy adult, but severe and painful. In individuals weakened by malnutrition or a pre-existing illness, tolerance is markedly lower.

In real life

The chanterelle/jack-o’-lantern confusion regularly causes reported poisonings in southern Europe, particularly around the Mediterranean basin, where the olive tree grows and mushroom foraging is a strong cultural practice. Cases are also documented in North America with the related species Omphalotus olearius and its cousins. Fungal bioluminescence, for its part, has inspired supernatural interpretations across many cultures: will-o’-the-wisps in European forests and forest lights in various Asian traditions often trace back to glowing mushrooms observed at night, whether Panellus stipticus in Japan or species of the genus Mycena in Central America. The rational explanation for these glows, rooted in fungal chemistry, was only established during the 19th century and fully developed in the 20th.

The fact-checker's eye

The show is accurate on the two essential points. The jack-o’-lantern mushroom is indeed bioluminescent and indeed toxic, and confusion with the chanterelle is a real, documented cause of poisonings. One detail deserves a nuance: the glow is only visible in total darkness and on fresh specimens. Mushrooms carried in a closed basket, away from any light source, could indeed emit a glow visible from outside if the container let light through. Under normal outdoor transport conditions or in a woven basket, the effect would be subtle but not impossible. The show thus builds on a real phenomenon, amplifying it slightly for the story’s needs. On the mycological front, the recommendation remains absolute: never pick a mushroom without positively identifying it, ideally with the help of a field guide or an experienced mycologist.

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Published on May 30, 2026

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