Soapy Knight

Description

The soapy knight is a fairly large mushroom with a cap 5–10 cm, of very variable colour: most often grey-green, but it can also be whitish, olive or almost blackish-brown. The cap margin is usually paler, the cuticle shiny, cracked in dry weather. The gills are sparse and whitish, the stem has no ring, and the distinguishing feature is the soapy smell.

It grows from September to November in coniferous and mixed forests, under firs and pines, sometimes in groups. In Poland it is common.

It is easily confused with knights, e.g. the charbonnier, and by its colour also with brittlegills. Clues are the soapy smell and flesh that turns red after a time, but these features can be indistinct. If in doubt, do not collect or eat it.

Identification features

Cap

Diameter 5–10 cm (descriptions also give 4–15 cm). Bell-shaped or hemispherical when young, then flat-arched, with the margin long inrolled, finally flat and wavy; with an indistinct low umbo. Fleshy, smooth, shiny, with a cracked cuticle in dry weather, sticky in wet weather. Colour extremely variable: most often grey-green, but from whitish, through olive and yellowish, to blackish-brown; margin usually paler, the colour fades with age.

Hymenophore (underside of the cap)

Gills widely spaced, slightly thickened, notched with a tooth (according to some descriptions attached with a notch), white at first, then yellow-grey, sometimes with a greenish tint; when damaged they turn black or pink (descriptions differ).

Stem

Height 6–10 cm (descriptions also give 4–12 cm), thickness 1–2.5 cm (descriptions also give 1–3 cm). Cylindrical or spindle-shaped, pointed towards the bottom, usually smooth, bare or scaly, sometimes with ochre spots; colour like the cap, but paler. No ring.

Flesh

Whitish, fleshy; reddish-flushed at the base of the stem, and some time after cutting it may turn red or pink-orange (an inconstant feature, often appearing after several hours). Smell distinct, soapy, compared to a freshly scrubbed floor. Taste described variously: sometimes bitterish-mealy, according to other descriptions mild; do not taste it.

Spore print and spores

Spore print white. Spores smooth, non-amyloid, broadly ellipsoid to oval. Size 5–7.5 × 3–5 µm (descriptions give different ranges).

Habitat and distribution

Ecology. A mycorrhizal, terrestrial fungus. Grows in coniferous and mixed forests (fir, pine, spruce), in Central and southern Europe also associated with oak; in the western United States also with live oak, tanoak and madrone.

Distribution. On all continents except Antarctica; common in Poland. Grows singly or in groups. Not legally protected in Poland.

Fruiting. From September to November (according to some descriptions from late summer to late autumn).

What can it be confused with?

• Tricholoma portentosum (charbonnier) — Cap grey-brown, not greenish; the soapy smell and the reddening of the flesh are not described.
• Tricholoma terreum (grey knight) — sometimes confused — Detailed differences — no data.
• Tricholoma griseoviolaceum — Listed as similar; detailed differences — no data.
• Brittlegills (Russula) — The stem of brittlegills is brittle and snaps easily; in the soapy knight it is fibrous and does not snap.
• Species of the genus Hygrophorus (waxcaps) — The gills may lead to confusion; 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 species name saponaceum comes from the Latin word meaning "soapy"; the French and German names sound similar (Seifenritterling).
• The cap colour is so variable that several varieties differing in colouring have been described; the species is probably a complex of at least two species.
• The characteristic features (smell, reddening of the flesh) often appear only several hours after collecting.
• The Polish name was proposed by Władysław Wojewoda in 2003.