Honey-yellow gilled mushrooms that fruit in dense clusters on stumps and roots. The underground network of a related species in Oregon (Armillaria ostoyae) is the largest known organism on Earth — spreading over 2,385 acres.

Also called: Honey Fungus, Stump Mushroom

Native status: Native; cosmopolitan in temperate forests

§ Quick facts

SizeFruiting body 5–30 cm diameter; massive clusters can be 1 m across
WeightIndividual caps 50–500 g; clusters often several kg
LifespanFruiting bodies 1–3 weeks; mycelial networks can persist for centuries
OrderAgaricales
FamilyLyophyllaceae

§ Encyclopedia

Armillaria mellea, commonly known as honey fungus, is an edible basidiomycete fungus in the genus Armillaria. It is a plant pathogen and part of a cryptic species complex of closely related and morphologically similar species. It causes Armillaria root rot in many plant species and produces mushrooms around the base of trees it has infected. The symptoms of infection appear in the crowns of infected trees as discoloured foliage, reduced growth, dieback of the branches and death. The mycelium is capable of producing light via bioluminescence.

Source: Wikipedia — Armillaria mellea Licensed under CC BY-SA 4.0

§ Identification

Field marks. Honey-yellow to brown mushroom; ringed stem; spore print white; ring of dark scales near base; growing in clusters at base of trees or on roots.

Similar species. Galerina marginata (deadly; rusty spore print). Pholiota species (different spore color). Other Armillaria species (require microscopy for definitive ID).

Voice. N/A

§ Diet & behavior

Diet. Saprotrophic and weakly parasitic: decomposes hardwoods and conifers; can kill stressed live trees.

Behavior. Various Armillaria species form some of the largest organisms on Earth — a single Armillaria ostoyae mycelium in Malheur National Forest, Oregon, covers 2,385 acres and is estimated at 2,400+ years old. Bioluminescent — the underground mycelium emits a faint green glow ("foxfire") seen at night on rotting logs in damp forests. Edible (with caution: cook thoroughly; some people get GI upset), but easily confused with toxic look-alikes including Galerina species (deadly).

§ Range

Throughout North America

§ Habitat

Decaying wood, tree roots — both saprophytic and parasitic on living trees

§ Threats

Forest fragmentation; conversely, these can be tree pathogens in stressed forests.

§ Conservation status

According to the IUCN Red List, the honey mushroom is currently classified as Least Concern.

§ What helps

Learn to identify edibles vs. poisonous lookalikes. Support diverse forests resistant to Armillaria attack.

Support our work More ways to help

§ Further reading

§ Sources cited

  • Mycological Society of America
  • USDA Forest Service
  • Oregon State Forestry (Malheur Armillaria)
  • North American Mycological Association