Agaricus bisporus
Also called white mushroom, cremini, portobello.
The button mushroom is the most widely cultivated mushroom in the world, sold white as button, brown as cremini, and fully opened as portobello. The same species grows wild in rich, disturbed ground, where it can be confused with white Amanitas.
Agaricus bisporus
Photo coming
The tell
Free gills that turn from pink to chocolate brown, a ring on the stem, and no cup at the base.
Field marks
Cap, underside and stem show in a photo. The spore print does not, and it is often the deciding check.
Where and when
Lookalikes
Each card says how to tell the two apart.
Amanita bisporigera
A destroying angel has gills that stay white, a white spore print, and a sac-like cup around the base of the stem, which is often buried in the soil. Button mushroom gills are pink to brown and its print is chocolate brown.
Agaricus xanthodermus
The yellow stainer turns bright chrome yellow when the base of the stem is cut or scratched and smells of ink or phenol. The button mushroom does not stain yellow and smells mild.
Chlorophyllum molybdites
The green-spored parasol is larger, has brownish scales on a white cap, and its gills age to grayish green, leaving a green spore print.
Agaricus campestris
A close wild relative that grows in grass and pastures. It has a thinner, more fragile ring and a slenderer stem, and its young gills are a brighter pink.
Edibility
Field guides list the button mushroom as edible, and it is sold in nearly every grocery store. Wild specimens belong to the same species. Poisonings tied to wild collections usually involve white Amanita species, which contain amatoxins that destroy the liver, or the yellow stainer, which causes gastrointestinal illness.
This page states what field guides record. It is not advice to eat, taste or handle anything, and a photo cannot settle edibility. If someone has eaten a wild mushroom that may be toxic, call poison control (1-800-222-1222 in the US) right away, before symptoms start: the deadliest species act hours later.
FAQ
Yes. Cremini are a brown strain of Agaricus bisporus picked young, and portobellos are the same brown strain left to open fully. White button mushrooms are a white strain of the same species.
Yes. Agaricus bisporus grows wild in compost, manure, gardens and disturbed ground across North America, and is most often reported in California. Wild collections are usually brown and scaly rather than smooth and white.
Look at the gills, the spore print and the stem base. A button mushroom has pink to chocolate brown gills, a chocolate brown spore print and a plain base. Death caps and destroying angels have white gills, a white spore print and a sac-like cup at the base.
Sources
MushroomExpert.com
MykoWeb, California Fungi
Index Fungorum
Also on Mushrooms.id
Stropharia rugosoannulata
A wine-red cap over purple-gray gills, with a thick ring whose underside is split into claw-like segments.
Agaricus fissuratus
Large white cap that slowly bruises yellowish, grayish pink to brown gills, a large ring with a cogwheel pattern beneath, and an anise smell.
Agaricus augustus
Large cap covered in golden brown fibrous scales, bruising yellow, with a big skirt-like ring and a strong almond smell.
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