Splendid Webcap Identification Guide

First Impression Under Beech

Splendid Webcap is a fungus of bright colour in a dim place. The setting is mature beech woodland on chalk or limestone, in late summer or autumn, where the litter is deep and the ground flora sparse. Against that brown floor the caps read as vivid chrome or sulphur yellow, glossy after rain, 4 to 10 cm across, usually scattered in small groups with fruit bodies at several stages of expansion. Because the species is ectomycorrhizal, the groups follow the root spread of particular trees, so once you find one you should search a radius of several metres rather than moving on. The overall build is stout: a firm fleshy cap on a solid yellow stem that ends in an abrupt swollen bulb, and the whole fungus feels heavy in the hand compared with the thin-fleshed woodland mushrooms around it.

Reading the Cap

Start with surface texture. The cap is viscid, tacky in damp conditions and shiny and slightly varnished-looking when dry, and litter fragments and beech leaf scraps commonly stick to it. Shape moves from hemispherical with a strongly inrolled margin to convex and finally broadly flattened, sometimes with a low umbo. The base colour is bright chrome-yellow to sulphur-yellow, and the diagnostic detail is the discoloration of the disc: mature caps typically develop a rusty-brown, ochre or olive-brown blotch or diffuse zone at or near the centre, sometimes as spots, sometimes as a broad wash, while the margin remains clean bright yellow. Wipe the cap clean before judging colour, because a film of debris will dull it. The margin may be finely wrinkled and, in young specimens, carries pale yellowish veil fibres that link it to the stem.

Reading the Gills and the Cortina

Webcaps take their name from the cortina, the cobweb-like partial veil that stretches from cap margin to stem in young fruit bodies. In this species that veil is yellowish and delicate. Find a button and confirm it before you look at anything else, because its presence places you in the genus and rules out large families of look-alikes in one stroke. In mature specimens the cortina is gone, but its remains persist as a fine fibrillose zone in the upper third of the stipe, usually stained rusty by trapped spores.

The gills themselves are crowded, moderately broad, and adnate to emarginate, often notched at the stem. They are bright chrome-yellow when young, an unusual and memorable shade, and they shift gradually to olive-yellow, then clay, then rusty cinnamon as spores mature, so a group of mixed ages shows the full colour sequence side by side. Gill edges may be slightly paler and finely eroded.

Stipe, Bulb and Flesh

The stipe is 4 to 9 cm long and 1 to 2 cm thick, solid, dry and fibrillose, coloured yellow along its length. At the base it swells abruptly into a marginate bulb, meaning the bulb has a distinct rim or shoulder where its upper edge flares outward like the base of a spinning top, rather than tapering smoothly. Check this by clearing away litter and lifting the whole fruit body: a rounded, non-rimmed base points elsewhere. Remnants of the yellowish universal veil often coat the bulb and its rim, and rusty spore fall may stain the shoulder brown.

Slice the fruit body vertically. The flesh is firm and sulphur-yellow throughout, particularly saturated in the bulb, which is one of the better confirmatory features. There is no strong or rapid colour change on cutting; the flesh may dull slowly to a duller yellow-ochre but does not turn blue, red or black. The odour is mild to slightly earthy, occasionally faintly sweetish.

Taking a Spore Print

Sever a mature cap where it joins the stem and lay it gills down on white paper for four to six hours under a cover. The deposit is rusty-brown to ferruginous, which is the defining spore colour for the whole webcap genus and the single most decisive test available in the field kit. Read it against white, not black. If your print comes out white, cream, pink or purple-brown you are not in Cortinarius at all, and every yellow-capped alternative below is settled at once.

Substrate, Season and Setting

This species forms mycorrhizal partnerships with broadleaved trees, above all beech, and it is closely tied to base-rich, calcareous soils. Chalk escarpment beech woods, limestone hangers, old beech avenues on lime-rich ground and mixed beech-oak stands on marl are the productive habitats. It fruits from late summer into autumn, favouring warm, wet spells, and is far commoner in central and southern parts of its range than in cool northern woods. In acid soils and conifer plantations, look for other yellow webcaps instead.

Separating the Look-alikes

Within the webcaps, the group of yellow viscid-capped species with bulbous stems is genuinely difficult and some determinations need microscopy. Cortinarius citrinus is paler, more greenish-lemon, with less contrast between margin and disc. Cortinarius elegantior and its relatives tend toward orange-ochre or olive-tawny tones with a browner overall cast rather than clean chrome yellow. Cortinarius odorifer carries a distinct aniseed odour and greener tints. If your fruit body has a dry, silky, tawny-orange to reddish-brown cap and a stem that tapers rather than ending in a rimmed bulb, you are in the Cortinarius orellanus and rubellus group instead, which shares nothing but the genus.

Outside the webcaps, the main confusions are quickly resolved. Yellow knight, Tricholoma equestre and its allies, has yellow gills and a yellow stem but no cortina at any stage, no marginate bulb, and a white spore print; it also favours sandy pine ground. Rustgills, Gymnopilus species, drop rusty spores like a webcap but grow in tufts on wood and carry a firm membranous ring rather than a cobweb. Hebeloma species are pallid buff to clay rather than chrome yellow, have a clay-brown print, and usually smell strongly of radish. Yellow-capped Amanita species can be excluded by their free white gills, white print and volva or ring.

Field Checklist

Beech, chalk, autumn; viscid chrome-yellow cap with a rusty-brown central blotch; yellowish cobwebby cortina in youth and a rust-stained fibrillose zone later; chrome-yellow gills ageing rusty; yellow stipe with an abrupt rimmed bulb; sulphur-yellow flesh, especially in the bulb; rusty-brown spore print. Six of these seven should be visible on any decent mature specimen.