Conocybe rugosa

A tiny brown lawn mushroom carrying the same amatoxins as the death cap. It grows in gardens, flower beds, wood chip mulch and other rich disturbed ground across Eurasia and North America, and its danger lies entirely in the mismatch between what it looks like and what it does — nobody expects a two-centimetre mushroom from a suburban lawn to cause liver failure. It has passed through several names and genera, appearing in the literature as Conocybe filaris, Pholiotina rugosa and Pholiotina filaris, and different guides will place it in different genera; they are the same fungus, and this site previously listed two of those names as separate species. It is most often encountered by people weeding a border or by parents finding mushrooms in a garden where small children play, and it is one of the few genuinely serious hazards in ordinary domestic ground.

What it looks like

Cap 1–2.5 cm, tawny to cinnamon-brown, conical then bell-shaped, sometimes finely wrinkled or grooved when moist and drying paler. Gills pale then rusty brown, crowded, narrowly attached. Stem very slender, pale brownish, and carrying a distinct membranous ring — unusual in this group of small mushrooms and the most useful feature it has, though the ring is fragile and often lost in older or weather-beaten specimens. Spore print rust-brown. It is small, thin-fleshed and entirely unremarkable, which is the whole problem.

Habitat

Lawns, flower beds, wood chip and other rich, disturbed ground.

Season

Spring to autumn.

Spore print

Rust-brown.

Family

Bolbitiaceae

Seasons are given for the northern hemisphere.

What it does to you

Poisonous in this game means: Toxic to humans — ranges from serious stomach upset to lethal.

Amatoxins, in concentrations that make a modest handful of these small mushrooms a serious ingestion. The clinical course is the same as the death cap's: six to twenty-four hours with no symptoms at all, then severe vomiting and diarrhoea, then a misleading recovery, then progressive liver failure. Because the mushroom is small, common in gardens and easily within reach, exposures involving young children are a recurring concern, and any suspected ingestion warrants immediate hospital assessment rather than waiting to see whether anything happens.

What it gets confused with

Numerous small brown mushrooms of lawns and mulch, including many harmless Conocybe and Bolbitius species, several inedible Agrocybe species, and the psychoactive Psilocybe species that people sometimes go looking for in exactly this habitat — a search that has caused amatoxin poisonings. Distinguishing small brown ringed mushrooms in a lawn to species is a job for a microscope. The practical response for anyone with small children is not to identify these but to remove them from the lawn.

Also published as Conocybe filaris, Pholiotina rugosa and Pholiotina filaris. Older guides may use any of them.