Butter Cap
Rhodocollybia butyracea
Also called buttery collybia, greasy toughshank, butter collybia
A late-season litter mushroom recognised by its greasy-feeling cap, crowded white gills, distinctly club-shaped stem base and pale pinkish spore print.
- Group
- Gilled
- Cap
- Smooth greasy cap, dark brown fading buff
- Spore print
- Pale pinkish cream
- Habitat
- Conifer needle beds and hardwood litter
- Season
- Autumn into early winter
Overview
Rhodocollybia butyracea, formerly Collybia butyracea, is a common autumn and early winter agaric of conifer plantations and mixed woodland. The genus Rhodocollybia was separated from Collybia on the basis of its faintly pink spore deposit and dextrinoid spores, characters that also make it the easiest way to confirm this species.
The English name refers to the surface of the cap, which feels slippery or soapy to the touch when damp, as though lightly greased. Two forms are usually recognised: the type form with a dark reddish-brown cap, and form asema with a grey-brown to smoky cap; both fade dramatically as they dry.
It is one of the last common litter mushrooms of the season, often still fruiting under conifers after the first frosts.
How to identify it
Cap
The cap is 3-7 cm across, convex then flattened with a low broad umbo, smooth and bald, and distinctly greasy or soapy to the touch when moist. It is strongly hygrophanous: dark red-brown or grey-brown when wet, drying from the centre outward to buff or pale tan so that fresh caps often show a two-tone zonation.
Gills
Gills are white to cream, narrow and crowded, narrowly attached to the stem or nearly free, with finely eroded or minutely serrated edges visible with a lens.
Stipe
The stem is 3-8 cm long, cartilaginous and hollow, tapering upward from a markedly swollen club-shaped base that is wrapped in white mycelial down. The surface is reddish brown, paler above, and finely fibrous or striate lengthwise.
Flesh and spore print
Flesh is whitish and watery. The spore print is pale pinkish cream to pale buff, a key character separating the genus from the white-spored toughshanks.
Where and when it grows
Butter Cap fruits in deep needle beds under spruce, pine and fir, and also in the leaf litter of broadleaved and mixed woodland. It grows scattered, in troops, or in loose clusters, and often appears in large numbers along path edges and in plantation rides.
The main season is autumn, extending into early winter and outlasting most other litter agarics. The species is common throughout Europe, temperate Asia and North America.
Ecological role
The fungus is a saprotroph of conifer needles and leaf litter, decomposing accumulated litter that many other fungi colonise only slowly. Its late season suggests tolerance of low temperatures, and fruiting frequently continues after frosts have ended other flushes.
The swollen, felted stem base sits within the litter mat where the mycelium is densest, anchoring the fruit body in loose needle beds that offer little support.
Similar species
Gymnopus dryophilus is similar in size and stature but has a dry cap, a stem of even thickness without the pronounced club-shaped base, and a white spore print. Rhodocollybia maculata is larger and whitish with rust-red spotting on cap and gills, though it shares the pinkish print.
Collybiopsis and Marasmius species in the same litter have tougher, more pliant flesh and white prints. Brown Mycena species are separated by their fragile flesh, more conical and finely lined caps, and slender stems without the felted, clubbed base.