Community find

Yellow-Staining Mushroom

Agaricus xanthodermus

Group

gilled mushroom

Spore print

Dark chocolate brown

Size

Cap diameter 5-15 cm; Stipe length 6-12 cm, width 1-2 cm.

Season

Typically appears from late summer through autumn, often after heavy rains.

Habitat

Found in gardens, lawns, parks, and along roadsides; often grows in clusters or fairy rings in grassy areas.

Distribution

Widespread throughout Europe, North America, and has been introduced to Australia and parts of Africa.

Key characteristics

White to off-white cap that often develops cracks or a tessellated appearance in dry conditions; turns yellow when bruised (especially at the base of the stem); dark brown gills at maturity; robust stipe with a ring.

Fruiting body

Cap: 5-15 cm diameter, initially hemispherical then flattening out, white surface often cracking into scales. Gills: Free, initially pink but turning dark chocolate brown as spores mature. Stipe: 5-15 cm long, cylindrical with a bulbous base, featuring a large, double-edged ring.

How to recognise it

Scratch the surface of the cap or the base of the stem to observe an immediate bright yellow stain; Note the distinctive 'phenol' or ink-like smell, which becomes stronger if the mushroom is crushed or heated.

Look-alikes

Agaricus bisporus (cultivated mushroom), Agaricus arvensis (Horse Mushroom), and Agaricus campestris (Field Mushroom). It is distinguished by its vivid yellow staining and a characteristic chemical odor.

Ecological role

Saprophytic, breaking down organic matter in the soil and grass.

Notes

The species name 'xanthodermus' is derived from Ancient Greek words meaning 'yellow skin.' It is one of the most common causes of misidentification among white mushrooms found in urban environments.