Petticoat mottlegillPanaeolus papilionaceus

The petticoat mottlegill (Panaeolus papilionaceus, often listed as P. sphinctrinus or P. campanulatus) is a small grey-brown mushroom of pastures that grows on old cow and horse dung. Its bell-shaped cap never opens out flat, white tooth-like scraps of veil hang from the rim like the lace of a petticoat, and the gills are mottled grey and black. It isn't edible.

How do you identify a petticoat mottlegill? The cap is 1.5 to 4 cm across, occasionally 5 cm, egg-shaped at first and then bell-shaped, grey-brown, pale brown or greyish, paling and often cracking as it dries. Young caps have white triangular teeth around the edge, but they rub off easily, so older caps may have lost them. The gills start grey and become mottled black as the spores ripen in patches, with white edges. The stem is long and slender, 5 to 12 cm tall and 2 to 4 mm thick, the colour of the cap or paler, finely powdered at the top, hollow and brittle, with no ring. The spore print is black.

Where does it grow? On old dung and dung-enriched soil in pastures, meadows and grazed commons, singly or in small groups. It's common, with finds from late spring, but most records come in autumn.

Is the petticoat mottlegill edible or psychedelic? It's not worth eating: it's small, thin and inedible. Lab analyses of the samples tested have not found psilocybin in it, although a few older reports from other countries claimed otherwise, and it may turn out to be a complex of similar species. So there's no reliable evidence that it's psychedelic. The real danger is its lookalikes: the same field can hold mushrooms that do contain psilocybin as well as deadly ones. If someone may have eaten an unknown little mushroom, get help straight away, even if they feel fine: call emergency services on 112 (999 in the UK) or your local poison centre and keep any leftovers.

What can you mistake it for? The liberty cap has a sharp nipple on the cap, unmottled gills and a purple-black spore print, no white teeth on the rim, and grows in grass rather than on dung. Some relatives, such as the banded mottlegill (Panaeolus cinctulus), do contain psilocybin, which makes them illegal in many countries. The egghead mottlegill is bigger and has a ring on the stem. The brown mottlegill (Panaeolina foenisecii) grows on lawns rather than dung and has a dark brown spore print. The most dangerous lookalike, Conocybe rugosa, contains the same amatoxins as the death cap: it's a small brown mushroom with a ring on the stem and a rusty-brown spore print, growing on wood chips, flowerbeds and compost. The fairy ring champignon, picked in the same meadows, has a white spore print and grows in rings in grass. So don't pick little brown mushrooms from pastures and lawns.