Butter Waxcap
Hygrocybe ceracea
Also called waxy butter cap, buttery waxcap
A small buttery-yellow waxcap with a slightly greasy cap, a dry stem and pale yellow gills that run a little way down the stipe.
Overview
The Butter Waxcap is one of the smaller yellow waxcaps of autumn grassland: a soft butter- to lemon-yellow cap rarely more than 3 cm across, on a slender dry stem of the same colour, appearing in scattered troops through mossy short turf. It looks like a miniature version of the Golden Waxcap and is often overlooked or lumped in with it.
As a member of Hygrocybe it shows the family signature of thick, soft, waxy, widely spaced gills and a white spore print. What sets it apart within the small yellow group is the combination of a cap that is only slightly greasy rather than truly viscid, a stem that is dry to the touch, and gills that are adnate with a distinct decurrent tooth — an intermediate gill attachment that is worth checking carefully in the field.
The yellow waxcaps are one of the harder parts of the genus, and H. ceracea, H. glutinipes, H. insipida and H. chlorophana are best separated by size, the presence or absence of slime on cap and stem, and the degree of gill decurrence.
How to identify it
Cap
Small, 1–3.5 cm across, convex then soon flattening and often becoming slightly depressed with a wavy margin. The surface is smooth, waxy and slightly greasy when damp but never coated in thick gluten, and the margin is translucently striate in wet weather. Colour is a clear butter-yellow to lemon or golden, sometimes fading to pale cream at the margin.
Gills
Thick, waxy and well spaced, adnate and typically with a short decurrent tooth running a little way down the stem. They are pale yellow to whitish-yellow, usually paler than the cap, and are often interveined near the stem apex.
Stipe
Slender, 2–5 cm tall and 2–5 mm thick, cylindrical or slightly flattened, dry and smooth, hollow and fragile. It is yellow like the cap, commonly whitish at the extreme base. There is no ring and no volva, and the stem is not glutinous, which is an important separator from Hygrocybe glutinipes.
Flesh and spore print
The flesh is thin, pale yellow and unchanging when cut, with no bruising reaction. The spore print is white and the spores are smooth and ellipsoid.
Where and when it grows
It grows in short, closed, unimproved grassland, particularly where moss is abundant: churchyards, old lawns, cemetery turf, unimproved pasture, upland grassland and dune slacks. It shows a slight preference for damper, mossier patches than some of its relatives, and can also appear on grassy woodland rides and banks.
The season runs from late summer through autumn, peaking in October, and the species usually fruits in small scattered troops rather than large flushes. It is widespread across temperate Europe and recorded in North America, and is a regular component of the waxcap assemblages used to assess the conservation value of old grassland.
Ecological role
The Butter Waxcap maintains a long-lived mycelium in grassland soil rather than decaying wood or coarse litter. Current evidence suggests that grassland waxcaps are biotrophic, obtaining carbon through associations with grassland plants or bryophytes, which fits the group's strong link to moss-rich, unfertilised turf and its resistance to laboratory cultivation.
Fruiting is triggered by autumn rain and cooling temperatures, and colonies typically reappear in the same square metre of turf across many seasons. Because the mycelium spreads slowly and is sensitive to fertiliser and ploughing, the species is a useful indicator of grassland continuity where it occurs alongside other waxcaps.
Similar species
Hygrocybe chlorophana, the Golden Waxcap, is larger, has a distinctly viscid cap and gills that are adnexed rather than decurrent. Hygrocybe glutinipes is similarly small but is thoroughly glutinous on both cap and stem, feeling slippery all over. Hygrocybe insipida is small and yellow-orange with a more orange centre and a viscid cap and stem, and Hygrocybe reidii is orange with a dry cap and a honey odour.
Small yellow Gliophorus species can be excluded by their thick slime coat, and yellow forms of Hygrocybe conica by the fact that they grey or blacken on bruising. The Butter Waxcap's own combination — small size, butter-yellow, only slightly greasy cap, dry stem and a short decurrent gill tooth — is the set to check against.