Stropharia pseudocyanea (Desm.) Morgan - Peppery Roundhead

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Agaricales - Family: Strophariaceae

Stropharia pseudocyanea - Peppery Roundhead

Stropharia pseudocyanea is one of very few blue-green fungi. (In some instances the caps are nearer to green than to blue, and with age they tend to become brownish, but when young and fresh they are very beautiful and, despite their small stature, quite startling.) The caps, initially bell-shaped, flatten and turn paler from the centre. What makes this species instantly recognisable and truly memorable is not so much its admittedly attractive appearance but its distinctive smell - exactly like freshly ground pepper..

Stropharia pseudocyanea in a Welsh churchyard

The Peppery Roundheads pictured above were found in a churchyard near Newtown, in Wales..

Distribution

Peppery Roundhead mushrooms are an occasional find throughout Britain and Ireland, occurring mainly in unimproved or semi-improved grassland. These striking mushrooms are also found in many parts of central and northern mainland Europe, and they are also recorded in western North America.

Taxonomic history

Although this little blue mushroom has been known to science for something like two centuries, its separation from Stropharia aeruginosa had not been clearly defined until it was described in a 1908 posthumous publication by American mycologist Andrew Price Morgan (1836 - 1907) and given its currently-accepted scientific name Stropharia pseudocyanea.

The basionym dates from 1823, when French naturalist John Baptiste Henri Joseph Desmazières (1786 - 1862) described this pretty little mushroom and gave it the binomial scientific name Agaricus pseudocyaneus. (In the early years of fungal taxonomy and naming, most gilled mushrooms were initially placed in the genus Agaricus, since slimmed down by transfer of the majority of former Agaricus species to other newer genera, including of course Stropharia.)

Synonyms of Stropharia pseudocyanea include Agaricus pseudocyaneus Desm., Agaricus albocyaneus Fr., Stropharia albocyanea (Fr.) Quél., Agaricus worthingtonii Fr., and Stropharia worthingtonii (Fr.) Sacc.

Etymology

Stropharia, the genus name, comes from the Greek word strophos meaning a belt, and it is a reference to the stem rings of fungi in this generic grouping. The specific epithet pseudocyanea means nearly blue, and it refers to the blue-green colouring of these grassland mushrooms.

Identification Guide

Cap of Stropharia pseudocyanea

Cap

Young caps are initially bell-shaped but soon flatten, usually retaining an umbo and expanding to between 2 and 4cm in diameter. The cap surface is blue-green and slimy, usually without marginal veil fragments (unlike Stropharia caerulea and Stropharia aeruginosa, which are also blue-green when young and fresh but generally much larger), turning white or pale brown with age.

Gills of Stropharia pseudocyanea

Gills

At first the colour of milky coffee, the crowded sinuate (notched near to the stem) gills turn greyish brown at maturity, but the gill edges remain almost white

 

Stem of Stropharia pseudocyanea

Stem

Whitish and fairly smooth above the ring, which is transient and soon disappears, pale and sometimes with white scales below the ring-zone. 2 to 5mm in diameter and 4 to 10cm tall.

 

Cheilocystidia of Stropharia pseudocyanea

Cheilocystidia

Clavate, 2-7µm diameter at the apex; often slightly capitate.

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Pleurochrysocystidia of Stropharia pseudocyanea

Pleurocystidia

Pleurochrysocystidia are clavate with a mucronate apex or occasionally lageniform.

Above: the pleurochrysocystidium shown here has been stained using PlaqSearch, which turns chrysocystidia deep blue rather than yellow (as when traditionally stained using ammonia).

Spores of Stropharia pseudocyanea

Spores

Ellipsoidal to ovoid, smooth, 7-10 x 4.5-5μm, without a germ pore.

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Spore print

Purple-black.

Odour/taste

Smells strongly of freshly ground pepper . (Caution: this species might be poisonous, so tasting is not advisable.)

Habitat & Ecological role

Saprobic, usually in small groups among grass in unimproved or semi-improved permanent pastures, old lawns, churchyards and parkland..

Season

July to October in Britain and Ireland.

Similar species

Stropharia aeruginosa is a larger blue-green mushroom and its cap scales are persistent; it has reddish-brown gills with white edges. This species is uncommon in Britain and Ireland. It does not have a peppery odour.

Stropharia caerulea is a larger, fairly common blue-green roundhead without a peppery odour.

Clitocybe odora is also blue-green but does not have a slimy cap with scales; it has a strong odour of aniseed.

Culinary Notes

Together with other fungi in the genus Stropharia, the Peppery Roundhead is inedible and may even be poisonous. Some of the Stropharia species can certainly cause very unpleasant gastrointestinal symptoms. We therefore treat Stropharia pseudocyanea as just for looking, and definitely not for cooking.

Reference Sources

Funga Nordica: 2nd edition 2012. Edited by Knudsen, H. & Vesterholt, J. ISBN 9788798396130

BMS List of English Names for Fungi

Noordeloos, M.E. (2011). Strophariaceae s.l. Edizioni Candusso: Alassio, Italy. 648 p.

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi and (for basidiomycetes) on Kew's Checklist of the British & Irish Basidiomycota.

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