Blackening Russula

Description

The Blackening Russula is a large, massive and very hard mushroom with a cap 5–20 cm across, depressed in the centre, with an inrolled margin. When young it is dingy white, then turns brown and finally black. The thick, widely spaced gills and the short, solid stem also darken with age. The most characteristic feature is the behaviour of the flesh: when cut or pressed, it first turns red, then grey and black.

It grows from July to November in deciduous and coniferous forests, including under beech and fir. In Poland it is fairly common.

In the field it is easily confused with other russulas that blacken when damaged, e.g. the crowded-gilled and white-black russulas. Collect only young, firm fruiting bodies; older ones have stringy flesh and are usually wormy. If you are not sure of the species, do not pick it or eat it.

Identification features

Cap

Diameter 5–20 cm (descriptions give different ranges); arched when young, later spreading and depressed in the centre, with an inrolled margin; very hard and thick-fleshed. The colour changes from whitish or dingy white through olive-grey and brown to black. The cuticle is slightly shiny.

Hymenophore (underside of the cap)

Gills very thick, brittle, widely spaced, plate-like, attached or slightly attached to the stipe. White or cream when young, darkening with age to black. When damaged they first turn red, then grey and then black.

Stem

Height 2–8 cm, thickness 1–5 cm (descriptions give different ranges); stout, cylindrical, solid and very hard, short compared with other russulas. Like the cap, it changes colour from white through brown to black; it turns red when pressed.

Flesh

Very hard, white; when cut it first turns red (light brick-coloured), then grey and black, usually within about 20 minutes. Smell weak, slightly insipid or fruity (descriptions differ), taste mild. The flesh should not be tasted.

Spore print and spores

Spore print white. Spores spherical to broadly obovate, 6–8 × 6–7 µm (descriptions give slightly different ranges), surface finely warty with a weakly defined reticulum.

Habitat and distribution

Ecology. A mycorrhizal fungus growing in deciduous and coniferous forests, including under beech and fir; in descriptions from Western Europe and North America mainly under conifers. The species is sometimes parasitised on old fruiting bodies by fungi of the genera Asterophora and Nyctalis (Nyctalis parasitica and Nyctalis asterophora are mentioned in descriptions).

Distribution. Europe, North and Central America, as well as Morocco, Korea, Japan and Australia. Fairly common in Poland. It is not legally protected in Poland.

Fruiting. From July to November (in Europe mainly late summer and autumn).

What can it be confused with?

• Russula densifolia (crowded-gilled russula) — More closely spaced gills.
• Russula albonigra (white-black russula) — Denser gills, bitterish-minty taste; blackens directly, without a reddening stage; rarer.
• Russula adusta (scorched russula) — In some descriptions: cap paler towards the margins, flesh turns red when cut but does not turn black. The extent to which the two species differ is disputed.
• Russula acrifolia and Russula dissimulans — They also turn red and then black when damaged; they require comparison of microscopic features and taste.

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 first description is by Pierre Bulliard in 1785, who named it Agaricus nigricans; the species name in the current genus was given by Elias Fries.
• The Polish name was given in 1876 by Feliks Berdau.
• Old fruiting bodies are often parasitised by fungi of the genera Asterophora and Nyctalis.
• In English descriptions, the smell of an old fruiting body is compared to empty wine barrels.