What You Should Know
Agaricus bitorquis is a choice edible white mushroom of the genus Agaricus which is similar to the common button mushroom that is sold commercially. It gets its common name from the habit of where it likes to grow, usually by sidewalks. Usually, in groups their size, they are quite sturdy and relatively easy to identify.
Agaricus bitorquis is recognized by its double annuli and frequently short and stout stature as well as a strongly inrolled pileus margin. The stipe is typically very firm, this is also a key feature. Similar to the common button mushroom A.Bisporus and regarded as just as tasty by most who have eaten it.
This mushroom does not turn yellow on bruising or cutting which rules out the poisonous Yellow Stainer (Agaricus xanthodermus) in the same family.
Agaricus bitorquis can be found usually in urban areas, in hard-packed soil; it is often found next to roads, on well-worn paths in parks, in ditches—and even pushing up through asphalt and concrete.
Other names: Sidewalk Mushroom, Torq, The Firm Champignon, The Banded Agaric, Spring Agaric.
Agaricus bitorquis Mushroom Identification
Saprobic; growing alone, scattered, or gregariously in hard-packed soil—along roadsides, near curbs, in parks, in ditches, and so on (also reported, not infrequently, to arise from cracks in concrete); summer and fall, or winter and spring in warm climates; widely distributed in North America.
4–11 cm; convex, becoming broadly convex or nearly flat; dry; bald; sometimes becoming cracked, roughened, or subscaly; whitish; rarely discoloring pinkish in old age or in wet weather; the margin not lined, and not yellowing when rubbed repeatedly.
Free from the stem; close or crowded; short-gills frequent; pinkish at first, becoming brown and then dark chocolate brown in maturity; covered with a white partial veil when in the button stage.
2–6 cm long; 1–3 cm thick; squat and very tough; equal or tapering to base; bald or finely roughened; with a tightly sheathing white ring that often flares outward on its upper edge—and sometimes with a double sheathing ring, or in some collections an almost volva-like sheath; whitish to brownish; not bruising.
White; firm; unchanging when sliced, or rarely turning slightly reddish (especially in wet weather).
Agaricus bitorquis Look-Alikes
Similar but can be distinguished by its salty odor and the red flesh when cut.
Has a more substantial single ring; it is usually taller for the same cap diameter.
Agaricus bitorquis Cultivation
Choose a suitable growing location. Mushrooms should be grown indoors where growing conditions can be controlled. A humid space is required, as relative humidity of 90% to 95% must be maintained throughout the growing process. When choosing a growing room, remember that mushrooms are grown in compost. You will want to choose a location that can get dirty and where you won’t be bothered by any residual smells. The optimal space will be one where ventilation is available but can be controlled or closed off if needed to prevent changing moisture levels or outside contaminants.
Prepare a growing tray by filling it with moist compost. The compost should be thoroughly wet but not soggy or dripping with water. Squeeze the compost between your thumb and forefinger to test it; at the proper moisture level, it will release two to three drops of water. Although the exact compost ingredients will vary from one garden center to another, it is important to use compost specifically sold as mushroom compost. Mushrooms get all of the nutrients they require from the compost so it must be made from a mix of materials that can provide those nutrients.
Mix the mushroom spawn into the compost. Mix well so that the spawn and compost are thoroughly combined. To calculate how much spawn you need, weigh the compost; the amount of spawn added should equal four to six percent of the compost weight. This should be about 1 to 2 cups of spawn for a growing tray that is 2 feet by 3 feet and 6 inches deep.
Maintain a temperature of 84 to 86 degrees Fahrenheit and mist the compost daily while checking the surface of the compost for a white, web-like appearance. This typically takes about 12 days to three weeks.
Place a 1 1/2- to 2-inch thick layer of peat moss on top of the growing tray when you see the white webbing appear. Cover the peat moss with newspaper and add water until the newspaper is moist.
Spray the newspaper twice a day with your mister to keep it moist for 10 days. Decrease the temperature in the growing area to between 75 and 77 degrees Fahrenheit at this time and for the remainder of the mushrooms' growth.
Remove the newspaper after 10 days but continue to mist the growing tray twice a day. In a few days, small mushrooms will sprout. Allow them to grow to the desired size and then harvest them. New mushrooms will form in their place in about two weeks.
Agaricus bitorquis Taxonomy and Etymology
Lucien Quélet gave this mushroom the specific name Bitorquis in 1883 (published in 1884) and named it Psalliota bitorquis.
In 1887, Italian mycologist Pier Andrea Saccardo (1845 - 1920) transferred it to the Agaricus genus.
The Latin bitorquis means "with two collars" - referring to the double ring created when part of the veil covering the young gills is torn from the brim, leaving a thin ring where the veil joins the two areas of the stem.
Agaricus bitorquis Synonyms
Psalliota bitorquis Quél., 1884
Pratella campestris var. bitorquis (Quélet) Quélet, 1886
Pratella bitorquis (Quél.) Quél., 1888
Fungus bitorquis (Quél.) Kuntze, 1898
Agaricus campestris subsp. bitorquis (Quél.) Konrad & Maubl., 1926
Agaricus campestris var. edulis Vittad., 1835
Psalliota edulis var. valida F.H. Møller, 1950
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