Medium to very large (rarely small) agaric, growing on the ground, occasionally among mulch, with a dark brown to purple-brown spore print. Pileus white to brown, smooth or becoming cracked with age, not viscid, not translucent-striate. Lamellae usually free, initially pink or cream, but always very dark brown when mature. Stipe central. Partial veil present, almost always forming a distinct annulus. Flesh often staining yellow or red. Spores yellow-brown, brown, grey-brown to black, non-amyloid, smooth; germ pore absent, rarely very faint. Cheilocystidia present or absent. Lamellar trama regular or interwoven. Pileipellis a cutis, rarely a trichoderm. Clamp connections absent.

Agaricus is distinguished from annulate species of Stropharia, with purple-brown or black spore print, by the free lamellae. Stropharia also has chrysocystidia, which are lacking in Agaricus, and spores that mostly have a germ pore (almost always lacking in Agaricus). When young, some species of Agaricus have very pale lamellae, and could be confused with Leucoagaricus, but this genus has a white or pale rather than brown spore print. Larger species of Coprinus, which can have an annulus, are deliquescent. Some annulate species of Agrocybe occur in similar habitats to Agaricus (lawns or mulch) but do not have free lamellae, and the pileipellis is a hymeniderm.

Agaricus L., Sp. Pl. 1171 (1753).

Seventeen species, and at least as many again to be named or recorded. In Australia are widely distributed species, often in gardens and disturbed habitats, such as A. arvensis (Horse Mushroom), A. augustus, A. bisporus (Cultivated Mushroom, also reported from the wild), A. bitorquis, A. californicus, A. campestris (Field Mushroom), A. devoniensis, A. impudicus, A. moelleri (= A. praeclaresquamosus, A. placomyces in sense of Australian records), A. rotalis, A. subrufescens, A. sylvaticus, A. silvicola and A. xanthodermus (Yellow Stainer). Species of native forests are poorly known: e.g. A. austrovinaceus (= Psalliota vinacea; close to A. langei), A. elatior (only known from the type specimen) and A. carminescens (only from Heron Island, Great Barrier Reef).

All States and Territories.

In parks, gardens, paddocks and plantations, along roadsides, and also in native forests.

On the ground, or among compost, rarely on litter or mulch.

Saprotrophic.

Bougher, N.L. (2006), The Hawaiian fungus Agaricus rotalis in Australia, Fungimap Newslett. 28: 4. [Description and Illustration of A. rotalis]

Bougher, N.L. (2009a), Fungi of the Perth region and beyond: a self-managed field book, Western Australian Naturalists' Club (Inc.), Perth. [Description and Illustration of A. californicus, A. campestris, A. rotalis and A. subrufescens]

Bougher, N.L. & Syme, K. (1998), Fungi of Southern Australia. University of Western Australia Press, Nedlands. [Description, Illustration and Microcharacters of A. bitorquis]

Brundrett, M., Bougher, N., Dell, B., Grove, T. & Malajczuk, N. (1996), Working with Mycorrhizas in Forestry and Agriculture. ACIAR Monograph 32. Australian Centre for International Agricultural Research, Canberra. [Illustration of A. placomyces]

Cappelli, A. (1984), Agaricus L.: Fr. ss Karsten (Psalliota Fr.), Fungi Europaei 1. Libreria editrice Biella Giovanna, Saronno. [Description, Illustration and Microcharacters and Key to 70 Euopean taxa of Agaricus, including all the cosmopolitan species known from Australia ]

Fuhrer, B. (2005), A Field Guide to Australian Fungi. Bloomings Books, Hawthorn. [Description and Illustration of A. augustus, A. austrovinaceus and A. xanthodermus]

Fuhrer, B. & Robinson, R. (1992), Rainforest Fungi of Tasmania and South-east Australia. CSIRO Press, East Melbourne. [Illustration of an unidentified species of Agaricus]

Grey, P. & Grey, E. (2005), Fungi Down Under. Fungimap, South Yarra. [Description, Illustration and Map for A. xanthodermus]

Grgurinovic, C.A. (1997a), Larger Fungi of South Australia. The Botanic Gardens of Adelaide and State Herbarium and The Flora and Fauna of South Australia Handbooks Committee, Adelaide. [Key to South Australian species, and Description and Microcharacters of A. arvensis, A. austrovinaceus, A. campestris and A. xanthodermus]

Heinemann, P. (1956), Champignons récoltés au Congo Belge par Madame M. Goossens-Fontana. II. Agaricus Fries s.s., Bull. Jard. Bot. État 26: 1–127. [Key, Descriptions and Microcharacters of 40 species, some cosmopolitan, others restricted to Africa]

Heinemann, P. (1974), Quelques Agaricus de Nouvelle-Zelandé, Bull. Jard. Bot. Nat. Belg. 44: 355–366. [Key, Descriptions and Microcharacters of six New Zealand species, none yet reported from Australia]

Heinemann, P. (1978), Essai d'une clé de determination des genres Agaricus et Micropsalliota, Sydowia 30: 6–37. [Key to species of Agaricus worldwide]

Leonard, P. (2009), Notes on Agaricus species in Queensland, Queensland Naturalist 47: 3–8. [Description, Microcharacters and B&W Illustration of A. impudicus and A. moelleri]

McCann, I.R. (2003), Australian Fungi Illustrated. Macdown Productions, Vermont. [Illustration of A. arvensis, A. campestris and A. xanthodermus, as well as several unidentfied species]

Shepherd, C.J. (1969), Observations on Australian Agaricales I. A preliminary account of the genus Agaricus L. ex Fr., Techn. Pap. Div. Pl. Indust. CSIRO 27: 1–20. [Key and Descriptions for nine species]

Shepherd, C.J. & Totterdell, C.J. (1988), Mushrooms and Toadstools of Australia. Inkata Press, Melbourne. [Description and Illustration of A. arvensis, A. campestris and A. silvaticus]

Young, A.M. (2005b), A Field Guide to the Fungi of Australia. University of New South Wales Press, Sydney. [Description and Illustration of A. augustus and A. xanthodermus, and Description and B&W Illustration of A. arvensis, A. augustus, A. campestris, A. xanthodermus]