Tricholoma atrosquamosum var. squarrulosum (Bres.) Mort. Chr. & Noordel. - Dark Scaled Knight

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

Distribution - Taxonomic History - Etymology - Identification - Culinary Notes - Reference Sources

A rare find in Britain and Ireland, Tricholoma atrosquamosum var. squarrulosum is a mycorrhizal mushroom of mainly deciduous woodland in areas of alkaline soil. Some authorities treat this mainly southern-Europe mushroom as a separate species Tricholoma squarrulosum (by which name it is generally referred to in the USA) because the autonomous variety found in Scandinavia and other parts of northern Europe (and probably not authentically recorded from Britain or Ireland) Tricholoma atrosquamosum var. atrosquamosum has significantly smaller spores and a stem with very few black scales.

Knights (Tricholoma species) are sometimes difficult to identify with absolute certainty, and unless studied very carefully less scaly specimens of Tricholoma atrosquamosum could easily be confused with other dark-grey knights such as Tricholoma terreum.

Distribution

Being a mycorrhizal mushroom, the fruitbodies recur in the same location year after year; however, in Britain relatively few such locations are known, mainly in southern parts of England and Wales. This beautiful mushroom occurs also in many parts of central and southern mainland Europe and in some parts of North America.

Taxonomic history

The basionym of this species dates from 1877, when Italian mycologist Pier Andrea Saccardo described this species and gave it the binomial nameTricholoma atrosquamosum., which remains its generally-accepted scientific name.

Synonyms of Tricholoma atrosquamosum include Agaricus atrosquamosus Chevall., Tricholoma terreum var. atrosquamosum (Sacc.) Massee, and Tricholoma nigromarginatum Bres.

Tricholoma atrosquamosum var. squarrulosum (Bres.) Mort. Chr. & Noordel., was first described in 1892 by Italian mycologist Giacopo Bresadola (1847-1929) and given the name Tricholoma squarrulosum. The generally-accepted (in Britain and Europe) name Tricholoma atrosquamosum var. squarrulosum dates from a 1999 publication in Persoonia by Danish mycologist Morten Christensen and Dutch mycologist Machiel Noordeloos (b. 1946).

Etymology

Tricholoma was established as a genus by the great Swedish mycologist Elias Magnus Fries. The generic name comes from Greek words meaning 'hairy fringe', and it must be one of the least appropriate mycological genus names, because very few species within this genus have hairy or even shaggily scaly cap margins that would justify the descriptive term.

The specific epithet atrosquamosum comes from Latin and means 'having black scales'; it refers to the blackish scales that cover the caps of these mushrooms.

Identification guide

	Cap Dark grey (sometimes almost black) and covered with recurved pointed scales; initially woolly and paler at the margin, the caps are convex at first, becoming broadly umbonate and expanding to between 4 and 10cm in diameter. The flesh of the cap and of the stem is greyish and does not change colour significantly on exposure to air.
	Gills Light grey at first, often developing black-spotted margins as they age, the gills are sinuate (notched near the stem). Stem Grey, covered with dense black scales; 4 to 8cm long, 1 to 1.8cm diameter; no stem ring.
	Spores Ellipsoidal, smooth, 6-8 x 3.5-6μm; inamyloid. Show larger image Spores of Tricholoma atrosquamosum var. squarrulosum, Dark Scaled Knight  X  Spore print White.
Odour/taste	Odour faintly mealy; taste mealy or slightly peppery.
Habitat & Ecological role	Ectomycorrhizal with deciduous broadleaf trees - mainly beech in Britain.
Season	Late summer and autumn in Britain; sometimes right through to December in parts of southern Europe.
Similar species	Tricholoma terreum and several other of the greyish knights could be mistaken for the Dark Scaled Knight is not examined very carefully.

Culinary Notes

Although reported to be edible and of moderate quality, Tricholoma atrosquamosum var. squarrulosum is very rare in Britain. We therefore do not consider that this species should be treated as a culinary collectible.

Reference Sources

Fascinated by Fungi, 2nd Edition, Pat O'Reilly 2016, reprinted by Coch-y-bonddu Books in 2022.

Kibby, G (2013) The Genus Tricholoma in Britain, published by Geoffrey Kibby

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

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.

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