Honey fungus

Description

The honey fungus forms large clusters of fruiting bodies on wood with honey-yellow to olive-brown caps (3–13 cm), covered with fine darker scales, densest in the centre. The gills are whitish, later beige-pinkish, and on the slender, bent stem there is a broad, membranous ring with a golden-yellow, fibrillose underside. The stems of neighbouring mushrooms fuse together, and the flesh is white and does not change colour.

It grows mainly from September to November, gregariously, on trunks, stumps and roots of trees, also in gardens and orchards. It is a dangerous tree parasite: it causes Armillaria root rot and can kill a tree. Sometimes the fruiting bodies grow from roots hidden in the ground and seem to grow straight from the soil.

Raw or undercooked it can be poisonous. Young caps are collected, and the hard, stringy stem is usually discarded. It is easily confused with the poisonous sulphur tuft, and other dangerous mushrooms also grow on wood, so collect only specimens you recognise with certainty.

Identification features

Cap

Diameter 3–15 cm (descriptions give different ranges). Young ones hemispherical or convex, then flattened, often with a low umbo, with age sometimes slightly concave; margin arched when mature. Colour honey-yellow, honey-brown or olive-yellow, then olive-brown to dark red-brown; appearance quite variable. Surface covered with fine red-brown, brown or blackish scales, densest and darkest in the centre; in old specimens the scales vanish and the cap is bare. A wet cap may be sticky.

Hymenophore (underside of the cap)

Gills thin, at first whitish, later beige-pinkish or yellowish with brownish spots, running down the stem or attached at a right angle (sometimes described as broad and fairly distant).

Stem

Height 5–20 cm, thickness 0.5–3.5 cm (descriptions give different ranges); slender, cylindrical, often bent, paler at the top, yellowish lower down, honey-brown to black-brown, widened at the base, rough and darker. The stems of neighbouring fruiting bodies often fuse into clusters. Ring broad, membranous, persistent, golden-yellow, with yellow fibrils on the underside; in young fruiting bodies it forms a white partial veil protecting the gills. With age the stem becomes hollow.

Flesh

Whitish, pale flesh-coloured, does not change colour when cut. In young fruiting bodies soft and fleshy, in old ones hard and stringy, especially in the stem. Smell faint, pleasant (compared to Camembert-type cheese); taste described as at first mild with an acrid aftertaste. Raw flesh should not be tasted; raw or undercooked it can be harmful.

Spore print and spores

Spore print white. Spores ellipsoidal, smooth, non-amyloid, with a distinct projection at the base; size 6–9 × 5–7 µm (descriptions give different ranges).

Habitat and distribution

Ecology. Saprotroph and tree parasite: attacks both dead and living wood, causing Armillaria root rot and white rot of wood. Grows on trunks, stumps, branches and roots, mainly of deciduous trees, but also infects conifers (especially young pine and spruce stands), as well as orchards, vineyards and gardens. Infects trees with rhizomorphs growing through the soil (up to about 1 m a year). It is also sometimes a host to other fungi; secondary parasitism of Entoloma abortivum on its fruiting bodies has been described.

Distribution. Temperate zone of the Northern Hemisphere; according to some descriptions on all continents except Antarctica and South America. Common in Poland. Fruiting bodies grow gregariously, often in great numbers, in forests, parks, gardens and orchards. Not legally protected in Poland; included in the list of mushrooms approved for sale (Ministry of Health, item 34).

Fruiting. Most often from September to November, sometimes already from the beginning of August.

What can it be confused with?

• Hypholoma fasciculare (sulphur tuft) — Regarded as poisonous and confused by inexperienced mushroom pickers. Also grows in clusters on wood, but has no persistent membranous ring; other differences — no data.
• Armillaria ostoyae (dark honey fungus) — Grows only on conifers, cap with distinct fibrils.
• Armillaria tabescens (ringless honey mushroom) — Has no ring on the stem; rare in Poland.
• Galerina marginata (funeral bell) — Not in the folder. A deadly poisonous species growing on wood, found among honey fungus; for differences see the verification notes.

Never rely on a single feature. If you are not sure — do not pick it; show the mushroom to a qualified mushroom expert.

Interesting facts

• The rhizomorphs of the honey fungus glow in the dark (bioluminescence of the mycelium); the activity has a daily cycle, with a maximum at about 17:30 and a minimum at about 7:30.
• Before dying, attacked conifers often produce exceptionally many cones and exude resin from the trunk.
• Whitish, deformed fruiting bodies looking like a malformed honey fungus are honey fungus fruiting bodies overrun by the parasitic fungus Entoloma abortivum; in 1974 it was thought the other way round, and a 2001 study showed that it is Entoloma that is the parasite.
• In one plum orchard a honey fungus spreading by rhizomorphs killed 600 trees within 6 years.