Common name: Wine-Cap Stropharia, Composter Mushroom, Burgundy Mushroom, Garden Giant, King Stropharia, Stone Mushroom.
Description and identifying characteristics: A red-burgundy/maroon-topped mushroom with dark-purple to purple-grey gills, and a stout, white stalk with a thick, wavy annulus (ring on the stalk). Fruiting bodies are comprised of convex or broadly, bell-shaped caps when young, to broadly convex to flat caps when mature. The caps can be from 5 to 37 cm (2 to 15 in) in diameter, with a 2-5 cm (1-2 in) wide stalk. The gills in young specimens start out pale when the mushrooms are immature, but as spores start to develop the color goes to purple-grey to purple-black. The spore print is purple-black in color. Microscopically, the spores are ellipsoid with a germ pore, 10-13 x 7.5-9 microns in dimension.
Often, thick white strands (i.e. rhizomorphs) can be seen emanating from the bottom of the stalk, and throughout the substrate from which the mushrooms are fruiting. Wine-caps grow individually, or in large clusters arising from wood-chips, wood-chip laden soil, or soil surrounding wood-chips. They are common in urban areas, often arising from landscaped areas or gardens.
Ecology/associated host or habitat: Wine-caps are saprotrophs, found in beds of wood-chips/mulch, especially in landscaped or gardened locations. These mushrooms are also commonly cultivated in wood-chips in urban environments.
Poisonous look-alikes: There are no reasonable look-alikes to this fungus; there are no other mushrooms that have a burgundy-red cap with purple gills. These characteristics alone will differentiate this mushroom from all other mushrooms.
Methods and Tips on harvesting: Wine caps are easily twisted off the substrate upon which they are growing. After removal, cut the stalks ½ inch above point of attachment to ground or above any dirt on the stalk. Brush specimens as you collect them with a mushroom brush in order to avoid getting any dirt in the gills of other specimens.
Wine-caps are favored by flies, which lay their eggs in the caps, so look for tiny holes in the stalk which indicate fly maggots are eating their way through the mushroom. Accordingly, dispose of any specimens who have holes in the stalks or caps.
Possible allergic reactions and symptoms: Wine-caps are considered edible and choice. As with other mushrooms and foods, however, some individuals may demonstrate a specific allergy to Stropharia rugoso-annulata.
As a general rule, to minimize the risk of allergic reactions, it is imperative that all mushrooms, including wine-caps, be cooked before consuming. It is recommended to limit your portion size whenever eating a species you’ve never eaten before. It is also advisable not to consume more than one new species of mushroom at the same time.
Special considerations for storage. As with other mushrooms, the storage of these mushrooms is best in containers that allow some gas exchange rather than containers do not. In other words, mushrooms are better stored in paper bags than plastic ones. Do not store this or any other mushroom in an airtight, Ziploc-type bag.
Photos:
Typical caps of Stropharia rugoso-annulata
Note the thick annulus
A group of wine-caps growing from wood-enriched soil
References:
Mushroomexpert.com
Rogers Mushrooms
Wildman Steve Brill