Surprise Webcap Identification Guide

The First Impression

The Surprise Webcap earns its name in a single movement. Walking through mossy conifer plantation or a damp heathy woodland edge in autumn, you pass a small, dull, olive-brown mushroom that looks entirely unremarkable — one of hundreds of little brown caps on the forest floor. Tip it over and the underside is blood-red to cinnabar, a shock of colour completely unheralded by the cap. That contrast between a drab top and a vividly red-gilled underside is the species in a sentence.

The habitat is part of the recognition. Look on acid, humus-rich soil among Sphagnum, Polytrichum or feather mosses, under spruce and pine, sometimes with birch mixed in, in the second half of the year. The fruitbodies are usually scattered or in loose troops, pushing up through moss rather than litter.

Reading the Cap

The cap is 2–5 cm across, occasionally to 7 cm, conical or bell-shaped when young, expanding to convex or flat and usually retaining a distinct pointed or broad umbo at the centre. The surface is dry and finely silky-fibrillose — with a lens you can see radiating innate fibrils — and it is matt, not viscid or glutinous.

Colour is olive-brown, tawny, yellow-brown or dull rust, often a little darker in the centre and slightly more yellow-olive toward the margin. Weathered caps fade toward ochre. The margin is usually even, sometimes minutely fringed with pale fibrils in young material.

The Gills and the Cortina

The gills are the point of the species:

• Colour: bright blood-red, cinnabar or deep crimson when young; as spores mature they become progressively dusted with rust and end up a muddy purplish-brown to cinnamon, though the red usually persists at the gill edge and in the depths between plates
• Spacing: moderately crowded to slightly distant
• Attachment: adnate to emarginate, sometimes with a fine decurrent tooth
• Edges: even, slightly paler

On a young fruitbody, look for the cortina: a fine, cobwebby veil of silky threads running from the cap margin to the stipe and covering the gills. It is ephemeral. In older specimens it collapses onto the stipe as a fibrillose zone that is stained rusty brown where spores have caught in it. Finding either the intact cortina or the rusty ring zone places the fungus in Cortinarius and is a necessary step in the identification.

Stipe, Base and Flesh

The stipe is 3–8 cm long, 0.4–1 cm thick, cylindrical or slightly widening downward, often somewhat flexuous, and stuffed then hollow. It is yellow to yellow-ochre — a clear, slightly greenish yellow rather than red — sometimes flushed olive or brownish with age, and covered with fine longitudinal fibrils. Above mid-height sits the rusty cortina zone.

Excavate the base rather than snapping the stipe. There is usually a conspicuous felt of bright yellow to chrome-yellow mycelium binding moss and needle litter to the stipe foot, and it is a valuable confirming character.

Split the fruitbody lengthwise. The flesh is pale yellow to straw in the stipe and cap, tinted reddish only in the gill tissue itself. It does not change colour appreciably on exposure. The odour is faint and radish-like or simply earthy.

Taking a Spore Print

Cut a mature cap free and set it gills-down on white paper, cover with a bowl, and leave for two to four hours. The deposit is rust-brown to cinnamon, sometimes with a faint reddish cast. This is one of the most decisive tests available: a rust-brown print combined with red gills eliminates every white-spored and purple-spored candidate immediately. Under the microscope the spores are ellipsoid, distinctly warty-roughened and about 6–8 × 4–5 µm.

Substrate and Season

Cortinarius semisanguineus is ectomycorrhizal, forming sheaths on the roots of conifers — spruce and pine in particular — and occasionally on birch. It cannot grow without a living partner tree, so it appears from soil in woodland and plantation, never on stumps, dead wood or compost. It favours acidic, humus-rich, well-mossed ground, and is common in upland conifer plantations, on heathy woodland margins, and in old pine woods.

The season runs from late summer to late autumn, peaking in September and October, and the species often refruits generously in the same mossy patches year after year.

Separating the Look-alikes

The red-gilled webcaps, historically grouped as Dermocybe, need to be split carefully on the colour relationship between cap, gills and stipe:

• Blood-red Webcap (Cortinarius sanguineus) — everything is deep blood-red: cap, gills, stipe and flesh. The Surprise Webcap's dull olive-brown cap and yellow stipe are the contrast that names it.
• Cinnabar Webcap (Cortinarius cinnabarinus) — bright brick to cinnabar cap as well as gills, and a species of broadleaf woodland, especially beech on calcareous soil.
• Saffron Webcap (Cortinarius croceus) — very similar cap and stipe, but the gills are yellow to olive-yellow or saffron, never blood-red.
• Orange-gilled webcaps (Cortinarius malicorius and allies) — gills orange rather than crimson, with orange-tinged fibrils on the stipe and often an olive cap.
• Rustgills (Gymnopilus spp.) — also rust-spored, but larger, brighter tawny-orange overall, usually with a scaly cap and a membranous ring, and growing on wood.
• Brownies and Tufts (Hypholoma spp.) — clustered on wood with purple-brown spore prints and no red in the gills.
• Milkcaps (Lactarius spp.) — some have reddish gills, but exude latex when the gills are scratched and give a pale cream spore print.

Field Checklist

Olive-brown silky umbonate cap; blood-red gills dulling to rust; cobwebby cortina or rusty ring zone; yellow fibrillose stipe; yellow basal mycelium; pale yellow flesh; rust-brown spore print; mossy acid soil with conifers in autumn.