Sepia Brittlegill Identification Guide

The find and the setting

Sepia Brittlegill is a mushroom of trodden ground rather than deep woodland. You usually meet it on the compacted margin of a woodland ride, along the mown verge of a parkland avenue, at the edge of a gravel car park under planted oaks, or in a churchyard where roots run under short turf. The first impression is unglamorous: a squat, dull grey-brown cap sitting almost flush with the soil, often half-buried, frequently crusted with grit and flattened leaf fragments, and looking somehow tired before it has finished growing. They rarely appear singly. Scan the same twenty metres of path edge and you will normally find a scattered troop of five or ten at different ages, the youngest domed and the oldest sunken and split.

Confirming the genus before the species

Settle the genus first, because it costs ten seconds and saves a long detour. Snap the stipe sideways: a brittlegill breaks cleanly and abruptly, like a stick of blackboard chalk, with no stringy fibres bridging the break. That texture comes from the rounded inflated cells packed through the tissue. Next brush a thumb across the gills; they crumble and shatter rather than bending. Then check the base for what is absent, since a brittlegill has no ring, no sheathing sac and no cobwebby veil. Finally, cut a gill and watch for a few seconds: nothing should seep from the cut. A milky or watery droplet would move you to the milkcaps instead.

Reading the cap

The cap is usually 4 to 9 cm across, convex at first, then flattening and finally dishing inwards at the centre. Colour is the sepia of an old photograph, a mid grey-brown that is darkest, sometimes almost blackish, over the central disc and washes out to a paler grey-buff towards the rim. In wet weather the surface is faintly greasy to the touch; in dry weather it is matt and slightly felted. The skin peels roughly half way in from the edge.

The single most useful cap character is the margin. In a mature specimen it is strongly and coarsely grooved, with furrows running 10 to 20 mm inwards and small blunt bumps standing between the grooves, so the rim looks pleated and lumpy rather than smooth. Hold the cap up to the light and those radial furrows are unmistakable. That grooved, tuberculate rim places the mushroom firmly among the drab brittlegills.

Gills, stipe, base and flesh

The gills are adnexed to almost free, moderately spaced rather than crowded, and unequal in length with a few forks near the stipe. Young gills are whitish, ageing to a dirty cream, and they very often develop rusty or greyish-brown spotting along the edges where they have been handled or grazed.

The stipe is short and stout, typically 3 to 6 cm long and 1 to 2 cm thick, white when it first emerges but quickly staining dingy grey-brown from the base upwards, most obviously on the side that touched the soil. Slice it lengthways and the interior of an older specimen is chambered and spongy, sometimes hollow. The flesh is white and does not redden or blacken; it simply drifts to a soft dull grey over some minutes. The base is blunt, not swollen and not sheathed, and usually carries a plug of adhering earth. The smell is a genuine character here: strong, earthy and oily, with a stale, cellar-like edge that becomes more obvious if you break the cap and cup it in your hands.

Taking and reading a spore print

Cut the stipe flush, lay the cap gills-down half on white paper and half on dark glass, cover it with a cup to hold humidity, and leave it three to six hours or overnight. Brittlegill prints are ranked on a fine colour scale from pure white through cream to deep ochre, so a thin, scattered dusting will mislead you into reading it too pale. Scrape the deposit into a small heap with a blade and judge that heap in daylight against white paper. Sepia Brittlegill sits at the pale end: white to at most a very pale cream. If your heap is a solid butter-yellow or ochre, you are somewhere else in the genus entirely.

Substrate, season and partners

This is a root-partner species, not a wood rotter, so it will always be growing from soil in reach of living tree roots. Oak is the overwhelming favourite, with beech, lime and hornbeam as secondary partners. It has a clear preference for heavy, compacted, base-rich ground, which is exactly why path edges, verges and worn picnic areas suit it so well. The season runs from July into October, and it is one of the earlier drab brittlegills to appear, often fruiting during a warm damp spell in high summer when little else is out.

Separating it from its closest relatives

Everything difficult here lives in the same group of dull, grooved-margin brittlegills, so work on measurable structure.

Russula amoenolens is generally smaller and more slender, with a warmer sepia-ochre cap, more crowded gills, a narrower stipe and a very distinctive smell that is nothing like the oily-earthy note of Sepia Brittlegill.

Russula pectinatoides is paler and yellower, more ochre-brown than grey-brown, with a slimmer stipe and finer, shorter marginal grooves; its gill edges are typically brown-spotted early.

Russula farinipes has a straw to honey-yellow cap and a stipe that is finely mealy towards the apex, and its gills are noticeably pliable and elastic rather than crisply brittle, which is odd for the genus and diagnostic once felt.

Russula foetens is far bigger, reaching 15 cm, honey to tan rather than sepia, with a distinctly glutinous cap in wet weather, an extremely coarse pleated rim and a hollow chambered stipe.

The blackening brittlegills, Russula nigricans and Russula densifolia, are separated instantly by flesh that reddens then blacks on cutting and by their thick, widely spaced gills.

A working checklist

Chalky snap in the stipe, shattering gills, no ring or sac at the base, no seepage from a cut gill. Sepia to grey-brown cap darkest at the centre, rim coarsely pleated for a centimetre or more. Cream-white gills spotting brown, short white stipe greying from the base, flesh greying but never reddening, strong oily-earthy smell. Very pale spore deposit. Compacted soil under oak, midsummer to mid autumn. That combination will land you on Sepia Brittlegill without needing a microscope.