Verdigris Agaric

Description

The verdigris agaric has a cap 2–8 cm in diameter, covered with slime of an intense blue-green colour, with white scales near the margin. With age the colour fades to yellow-ochre, and on dry days the cap becomes smooth and shiny. The gills are at first whitish, then violet-blue, finally chocolate brown. The stem is white or pale beige, and below the fragile, quickly disappearing ring it is covered with white scales.

It grows in groups from September to November in deciduous and coniferous forests, in parks, in gardens on wood chips and along roads, on soil and on dead wood. In Poland it is common.

It is distinguished from Stropharia caerulea, which has a bluer, less slimy cap and pinkish gills. The edibility of the species is disputed and its chemical composition is poorly known, so it is not recommended for collecting for the table.

Identification features

Cap

Diameter 2–8(10) cm; convex when young, then bell-shaped to flat, with a broad umbo with age. The surface is covered with a layer of slime, at first intensely blue-green or bluish green, with white scales (veil remnants), especially near the margin. With age or after the slime is washed off, the colour fades to yellow-ochre, often in patches, first in the centre, and eventually the greenish-blue tint disappears completely. In dry weather the cap loses its slime and becomes smooth and shiny. The cuticle peels off easily.

Hymenophore (underside of the cap)

Gills crowded, adnate to the stem; covered by a veil in young fruiting bodies. At first whitish, then violet-blue to clay-brown, finally chocolate brown. Gill edges white, powdery.

Stem

Height up to about 8 cm, thickness up to 1 cm, cylindrical, hollow inside. Colour pale beige, whitish or pale greenish, turning brownish with time. Ring at mid-height, fragile, brownish to blackish, disappearing early. Below the ring the stem is covered with fine white fibrils or scales.

Flesh

Greenish white, then cream, fairly firm. Taste and smell indistinct (slightly acrid according to some descriptions). The flesh should not be tasted.

Spore print and spores

Spore print violet-brown (brownish violet). Spores elliptic-ovoid, about 7–10 × 4–5.5 µm (descriptions give different ranges).

Habitat and distribution

Ecology. Saprotroph growing on soil, on dead wood, in leaf litter and on wood chips; forms groups of many fruiting bodies. In Poland it most often grows under beech, less often under fir. It readily occurs on wood-chip mulch in gardens and parks.

Distribution. North America, Europe (including Great Britain) and Iran. In Poland common or fairly common: deciduous and coniferous forests, parks, grassy woods, roadsides. It is not legally protected in Poland.

Fruiting. In Poland usually from September to November (from spring to autumn according to some descriptions).

What can it be confused with?

• Stropharia caerulea (Polish: pierścieniak białoniebieski) — Cap bluer, gills pinkish, less slimy.
• Stropharia pseudocyanea — Smaller and more delicate, grows in grassy habitats, ring very fleeting.
• Psilocybe species — They stain blue when damaged and have a stem without scales.

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 epithet aeruginosa means "covered in verdigris" in Latin, i.e. the green coating on copper; hence the Polish name of the species.
• The intense blue-green colour of the cap comes from the slime and fades with age or after rain, which is why old fruiting bodies are yellow-ochre.
• In 2025 the Commission for Polish Fungal Nomenclature accepted the name "pierścieniak niebieskozielony".
• It readily grows on wood-chip mulch in gardens and parks.