A woodland Agaricus in the yellow-staining group (section Xanthodermatei), with a pale cap covered in grey-brown scales that are densest at the center. It bruises yellow and smells unpleasantly of ink or phenol. It upsets the stomach in many people. The well-documented range is Europe. North American material once called A. meleagris is unresolved: Kerrigan (2016) places the eastern flat-topped yellow-stainer in A. placomyces and does not list A. moelleri for North America.
Poisonous to many people: a gastrointestinal irritant of the A. xanthodermus type, causing stomach upset even after thorough cooking. Some people eat it without obvious effects, but it should not be eaten. It can be mistaken for edible field mushrooms such as A. campestris, which do not turn yellow when bruised or cut and lack the ink-like odor.
Never eat a wild mushroom based on a web page — confirm with an expert.
Habitat
Saprobic, singly or in small groups in deciduous and mixed woodland, parkland and under hedgerows; prefers rich, alkaline soils. In Britain and Ireland it fruits from July to November.
Distribution
Widespread in Europe, from northern Scandinavia to the Mediterranean, including Britain and Ireland; Wikipedia also gives temperate Asia and parts of North America. North American reports are doubtful. First Nature says it is unclear whether American and European material is the same species. Kerrigan's 2016 monograph of North American Agaricus does not list A. moelleri: it treats the eastern flat-topped yellow-stainer as A. placomyces and lists western North American 'praeclaresquamosus' concepts as unresolved.
Characteristics
Cap: 3-10 cm, globose at first, then convex and flattening; whitish with grey-brown scales concentrated at the center; yellows when bruised, mainly toward the margin. Gills: free, crowded, pale pink when young, becoming pink and then brown. Stem: 1-2 cm thick, smooth and silky, with a bulbous base; large, white, pendulous ring that turns bright yellow when bruised. Flesh: white; cut flesh in the stem base turns yellow, then slowly brown. Odor: unpleasant, like ink, phenol or carbolic soap, strongest when cut. Spore print: brown. Spores: 4.5-6.5 x 3.5-4 µm, ellipsoid, smooth (First Nature).
