Wine Cap Identification Guide

First impressions and where you are standing

Wine Cap is a fungus of disturbed, mulched, human-made ground, and the setting is a large part of the identification. You are typically standing on a bed of fresh or half-rotted wood chips: a landscaped path in a park, a shrub border in a garden, a newly mulched roadside planting, a straw-mulched allotment bed, or a heap of chipped brash at the edge of a wood. Very rarely do you meet it in undisturbed woodland soil.

The first impression is of scale and colour. This is a large, solid mushroom, with caps commonly eight to fifteen centimetres across and occasionally much wider, standing on a thick white stem. Young caps are a deep wine-red, burgundy or reddish-brown, and they look almost varnished when moist. Older caps fade markedly to tan, clay-buff or almost dirty straw, which is why colour alone is not enough and the ring and gills have to be checked.

Reading the cap

Start with shape. The cap is strongly convex and dome-like when young, sometimes almost hemispherical, and expands to broadly convex then flat, often becoming slightly depressed at the centre in very old specimens. The margin is inrolled at first and frequently carries fine white veil remnants that soon vanish.

The surface is smooth and dry to slightly greasy, never truly slimy. Fresh caps are that characteristic vinous red-brown; sun and age bleach them from the centre outward, so a single troop can show everything from deep burgundy to pale tan. In dry weather the cuticle often cracks into fine radial or areolate fissures, particularly across the disc, giving an aged specimen a scuffed appearance.

Cap flesh is thick, firm and white, and it stays white when cut. There is no blueing, no reddening and no significant discolouration in the cap flesh, and that stability is itself a useful character.

The gills

Turn the mushroom over and look at the attachment. The gills are attached to the stipe, adnate to slightly sinuate or with a small decurrent tooth - they are not free, and separating them mentally from the free-gilled genera is the single most important step.

Colour changes dramatically with age and gives an instant read on maturity. Very young gills, once the veil breaks, are whitish to pale grey. They pass through lilac-grey and slate-grey to a deep purple-brown or almost blackish-purple in maturity, and the change is uneven, so a mature cap often shows a mottled dark-and-pale pattern across the gill faces. The gill edges usually remain paler than the faces, whitish and finely uneven under a lens, and this pale edge on a dark face is a good confirming detail.

Gills are crowded and moderately broad, with several tiers of shorter gills interleaved.

Stipe, ring and base

The stipe is stout, white to cream, typically eight to fifteen centimetres tall and one and a half to three centimetres thick, often thickening downwards into a slightly swollen, club-shaped or bulbous base.

The ring is the character to spend time on. It is thick, membranous and persistent, set high on the stipe, and the upper surface is strongly radially grooved or furrowed. The underside, where it flares away from the stipe, splits into stiff triangular segments so that the ring appears cogged or star-shaped - the so-called cogwheel ring that gives the species its scientific epithet. Look at a ring on a young specimen before it has collapsed, because in weathered material the segments break away and the ring can look like a plain skirt. In dark-spored maturity the top of the ring is usually dusted purple-brown with fallen spores.

The base is the second key. Excavate it carefully rather than snapping the stem. You will find the base attached to thick white mycelial cords or rhizomorphs that run out into the wood chips, sometimes for a considerable distance, binding chips into a mat. There is no volva, no sac and no free-standing membranous cup, although a thickened basal swelling can superficially suggest one until you look closely.

Stipe flesh is white and solid at first, becoming stuffed or hollow with age. Cut surfaces may pick up a faint yellowish or dingy tone over time but show no strong reaction.

Taking and reading a spore print

This species prints heavily and quickly. Cut the stipe flush with the gills, set the cap gills-down on white paper, cover, and leave it two to four hours; a mature cap can produce a solid print in less.

The print is dark purple-brown, sometimes described as blackish-purple or purple-grey. Look at a thin edge of the deposit against white to judge the tone accurately, because a thick print looks simply black. This colour is decisive: a chocolate-brown print points to a different genus, a rusty-brown one to another, and a pink or white one excludes the species entirely.

Spores are smooth and ellipsoid with a distinct apical germ pore, which is worth confirming if a microscope is available.

Substrate and season

Wine Cap is saprotrophic on woody debris and straw, and it thrives in nutrient-rich, disturbed, mulched habitats. Fresh hardwood chip is the classic substrate, but it also fruits in straw mulch, sawdust, garden compost, mixed leaf-and-chip mulch, and along woodland tracks where chipping has taken place. It is a fungus that follows machinery and landscaping rather than ancient habitat.

Fruiting runs from late spring through summer and into autumn, with the biggest flushes on newly laid mulch beds one to two seasons old. Fruit bodies commonly appear in troops or loose clusters, and a productive bed can push up dozens over a few weeks. Because the substrate is often watered in gardens, it can fruit in dry spells when woodland fungi are absent.

Separating it from the look-alikes

Agaricus species share the stature, the white stipe and a membranous ring, and they also grow in enriched ground. Separate them on gill attachment and print colour: Agaricus gills are free of the stipe and the print is a warm chocolate-brown, not purple-brown. Agaricus rings are also smooth or cottony beneath rather than cogged, and many species show pink young gills and yellowing or reddening flesh.

Other Stropharia species share the dark purple-brown print. Stropharia aeruginosa and its relatives are blue-green and slimy-capped, and much smaller. Stropharia coronilla is small, yellowish and grows in grass with a grooved but uncogged ring. Stropharia hornemannii is large but has a distinctly viscid cap and a strongly scaly lower stipe, and grows on conifer debris.

Cortinarius species can be similar in size and colour, but the young cap edge is joined to the stem by a cobwebby cortina rather than a membranous ring, mature gills and the ring zone are rust-brown, and the print is rusty brown.

Agrocybe species also colonise wood chips and carry a ring, but they are smaller, with tan to ochre caps, and the spore print is a dull brown rather than purple-brown.

Pholiota species on wood chips are usually scaly-capped, yellow to tawny, and give brown prints.

Quick field checklist

Large burgundy-fading-to-tan cap, attached gills passing from grey to purple-brown with pale edges, thick white stipe, a high membranous ring that is grooved above and cogged beneath, white mycelial cords in the substrate, wood chip or straw mulch, and a dark purple-brown spore print. All seven together are conclusive.