Banded Mottlegill Identification Guide

The Setting

Open, enriched, disturbed ground. Manured lawns, well-fed pasture, racecourse verges, compost heaps, straw-mulched beds, wood-chip paths, allotment margins, and the grassy edges of stock yards and stables. Spring through autumn in temperate regions, and effectively year-round where winters are mild, with the biggest flushes appearing three or four days after a warm rain.

The typical encounter is not with one mushroom but with a scattered troop: dozens of small brown caps standing across a patch of short grass, sometimes loosely clustered where the substrate is richest, occasionally in an irregular arc.

First Impression

A small, plain brown mushroom on a long, thin stalk, standing straight rather than leaning. Young caps are dome-shaped or bluntly conical; older ones flatten. The whole fruit body looks fragile without being papery, and the stalk seems too thin for the cap it carries.

What stops an experienced eye is the gills. Even from above at an oblique angle you can see they are not uniformly coloured but blotchy — patchy black on grey. That mottling is the character the common name and the genus both rest on.

The Cap

One and a half to five centimetres across. It begins hemispherical to bluntly conical, expands to broadly convex, and finishes almost flat, occasionally with a very low broad umbo. The surface is smooth: no scales, no fibrils across the disc, no slime.

The cap is strongly hygrophanous, and this produces the second half of the common name. Fully moist, it is a rich dark reddish-brown, chestnut or cinnamon. As it loses water it pales from the centre outward to buff, tan or dull cream, and for a period during that transition a distinctly darker band of still-moist tissue remains around the margin, ringing the pale disc. Catch a group at the right moment and half the caps show the band.

In dry weather older caps can crack into fine plates or become finely wrinkled. Veil remnants are usually absent altogether, though very young caps sometimes carry a few pale fibrils on the extreme margin.

The Gills

Attached to the stalk — adnexed to adnate, sometimes with a slight notch — moderately close, broad, and rather thick for a mushroom this size.

The colour progression is the genus signature. Young gills are pale greyish-brown. As the spores mature they do so unevenly, in patches, so the gill face becomes marbled and cloudy, with dark and light areas side by side. At full maturity the gills are nearly black. Put a lens on the gill edge and you will see it stays finely white and floccose, contrasting sharply with the dark face — a small feature but a useful one.

The Stipe

Four to ten centimetres long, occasionally twelve, and only two to four millimetres thick. It is equal or very slightly thickened at the base, hollow, and brittle enough to snap cleanly rather than tear.

The surface is pale buff to reddish-brown, finely silky-fibrillose along its length, and minutely powdery at the extreme apex. Many collections are noticeably reddish-brown or rusty in the lower half and paler above. There is no ring and no ring zone. At the base, white mycelial threads usually bind grass roots, straw fragments and soil into a small mat.

Flesh and Colour Change

Thin and pale brownish, watery in the cap and fibrous in the stalk. On cutting there is generally no dramatic change. Some collections develop a faint greenish or bluish tinge at the stalk base or where the fruit body has been handled or bruised, appearing over several minutes; note it as a character if present, but its absence is not an objection.

Taking a Spore Print

Essential here, and quick. Cut a mature cap and lay it gills-down on white paper — or better, on a sheet half white and half black, which lets you judge dark deposits accurately — cover with a glass or bowl, and leave two to four hours. This species drops spores readily and you rarely need to wait overnight.

The print is jet black. A smear on white paper looks like soot, with no brown, no rust, and no purple cast when you look at a thin edge of the deposit against the light. That one result removes an enormous number of candidates in a single step.

Microscopically the spores are large for the size of the mushroom: 11–14 by 7–9 micrometres, smooth, lemon-shaped in face view and somewhat flattened in side view, very dark under the lens, and each with a broad germ pore at the narrow end.

Substrate, Ecology and Season

The fungus is saprotrophic, breaking down dead plant material where the ground has been enriched with dung, compost or rotting straw. Unlike some of its relatives it is not usually found sitting on a dung pat itself; more often it fruits from enriched soil, spent compost, mulch, straw or wood chips a little distance from the source.

That preference explains its distribution: it is cosmopolitan and strongly tied to land people manage, appearing wherever grazing animals, manure spreading, composting or heavy mulching concentrate nutrients. Fruiting runs from spring through late autumn, with mild-climate populations producing in winter too.

Separating It from Look-alikes

Panaeolus papilionaceus and P. sphinctrinus. They share the mottled gills and the black print, but their caps are grey to grey-brown rather than warm reddish and are not conspicuously banded, and the cap margin is hung with small triangular white veil teeth. They sit directly on dung far more often.

Panaeolina foenisecii, the lawn mower's mushroom. The trap. It grows in the same lawns, at the same time, at the same size, with a similarly hygrophanous cap that also shows a darker marginal band. Take a print. The deposit is dark brown with a purplish cast, never jet black, and under a microscope the spores are roughened or warted rather than smooth. Never skip the print on a small brown lawn mushroom.

Panaeolus fimicola. Smaller and greyer, with a fine dark band around the cap margin, typically on dung or dung-enriched turf.

Panaeolus semiovatus and P. antillarum. Much larger and paler, with tan to whitish ovoid caps that often wrinkle as they dry, growing directly on dung; the first has a distinct ring on the stalk.

Psathyrella species. Very fragile, often with white veil fibrils along the cap edge, gills that darken evenly rather than in mottled patches, and prints that are dark purplish-brown to blackish-brown. Their stalks are usually white and even more brittle.

Protostropharia semiglobata. Viscid yellowish hemispherical cap, a ring zone on a long slender stalk, and a purple-brown print.

Deconica species. Prints are purple-brown to violet-black rather than jet black, and their gills darken evenly instead of mottling.

Conocybe and Pholiotina. Rusty-brown prints, conical caps, and even more slender stalks.

Agaricus species. Gills free from the stalk, a chocolate-brown print, and a well-formed ring.

Field Checklist

Small hygrophanous cap, dark reddish-brown when moist and drying pale with a lingering darker marginal band; mottled grey-and-black gills with white edges; slim hollow ringless stalk; jet-black spore print with smooth lemon-shaped spores; growing in troops on manured grass, compost, straw or mulch.