Wood mushroom

Description

The wood mushroom (also called the bulbous or flat-bulbed agaricus in Polish) is a white, silky-shiny agaricus with a cap 6–14 cm across and a low umbo. It turns yellow when touched or cut and smells pleasantly of aniseed or almonds. Its stem is slender, bent, with a thin, hanging ring and a distinctly widened, bulbous base. The gills are initially whitish, then greyish-red and dark brown.

It grows from July to October, usually singly, in pine and spruce forests, also under beeches, and likes grassy edges. In Poland it is fairly common. It accumulates cadmium, so it should not be eaten in large quantities and often.

Young, still closed fruiting bodies can be confused with deadly poisonous amanitas; the base of the stem decides (a volva in the amanita). Also distinguish it from the yellow stainer, which smells of phenol. If you have doubts, do not pick or eat it.

Identification features

Cap

Diameter 5–15 cm (descriptions give different ranges), somewhat smaller than in the horse mushroom. Initially hemispherical, later opening umbrella-like, with a weak, blunt umbo; fairly fleshy. Colour white, sometimes whitish-cream, sulphur-yellow or ochre-yellow. Surface from silky to finely fibrillose, even fibrillose-woolly. Turns yellow when pressed or damaged (according to some descriptions yellow-ochre).

Hymenophore (underside of the cap)

Gills free, very crowded; whitish in young ones, then greyish-red, finally dark red to blackish-brown.

Stem

Height 5–15 cm (descriptions give different ranges), width 1.5–3 cm; slender, cylindrical, somewhat tapering towards the top, silky fibrous above the ring. Mostly bent above the bulb, characteristically widened into a bulb at the base. Ring very thin, hanging, edged from below with leathery warts (according to some descriptions fragile). Colour similar to the cap. No volva at the base.

Flesh

In the cap white, very thin, with a cavity near the stem; turns yellow when cut or crushed. Smell pleasant, aniseed or almond; the aniseed smell disappears on cooking and is caused by a small amount of a mixture of benzyl alcohol and benzaldehyde. Do not taste wild specimens.

Spore print and spores

Spore print purplish-brown to brown. Spores elliptical, smooth, 6–7.5(8) × 4–5.5 µm, without a germ pore. Schäffer's reaction and KOH reaction positive (like other species of section Arvenses).

Habitat and distribution

Ecology. Terrestrial saprotroph in pine and spruce forests, also under beeches, fond of grassy edges among coniferous litter; grows mostly singly (according to some descriptions also in deciduous forests, usually a few specimens or singly). The species can accumulate cadmium — its concentration in the fruiting body may be up to 300 times higher than in the soil.

Distribution. North America and Europe (including Great Britain); according to some descriptions also Bangladesh and Pakistan. Fairly common in Poland. It is not legally protected in Poland; it appears on the list of fungi approved for sale (Ministry of Health item 43, as A. silvicola).

Fruiting. From July to October (summer to late autumn).

What can it be confused with?

• Amanita virosa (destroying angel) and young Amanita phalloides (death cap) — Young, conically closed fruiting bodies can be confused with the deadly poisonous destroying angel. In the amanita the cap skin does not turn yellow when damaged, and the base of the stem has a volva; the gills of amanitas stay white. The species also looks similar to the young death cap.
• Agaricus arvensis (horse mushroom) — Its gills never have a pink tinge.
• Agaricus xanthodermus (yellow stainer) — Inedible; smell of carbolic acid, flesh turns strongly yellow when damaged.
• Agaricus campestris and other agaricus mushrooms of section Arvenses (e.g. A. albolutescens, A. abruptibulbus, A. osecanus, A. subrutilescens) — Listed as similar; detailed differences — no data.

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 aniseed smell is caused by a small mixture of benzyl alcohol and benzaldehyde.
• The species can accumulate cadmium at a concentration up to about 300 times higher than in the soil.
• In 2025 the Commission for Polish Fungal Nomenclature of the PTMy recommended the name "pieczarka płaskobulwkowa".
• Originally described as a variety of the field mushroom: Agaricus campestris var. sylvicola (Vittadini, 1832).