Tricholoma portentosum (Fr.) Quél. - Coalman

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

Tricholoma portentosum

An occasional find, often in small tufts joined at the stem bases, with conifers and in particular pines on sandy soil, Tricholoma portentosum is a chunky mushroom with an umbonate form typical of the Tricholoma genus. A (usually darker) form of this mushroom is also reported from broadleaf woodland, particularly with Beeches.

The specimens shown on the left and immediately below were found during late October and early November beneath Scots Pines in the Caledonian Forest near Aviemore, Scotland.

Although Tricholoma portentosum is now included in the BMS list of English Names for Fungi as Coalman, some people still refer to it as either the Dingy Agaric or the Streaky Tricholoma.

Distribution

Fairly common in Scotland but increasingly scarce further south in Britain and in Ireland, where the distribution is very patchy, Tricholoma portentosum occurs also throughout northern and central mainland Europe; it is also found in North America, where it is commonly referred to as the Sooty Head.

Tricholoma portentosum in moss beneath a Scots Pine, Caledonian Forest

Taxonomic history

When he described this species in 1821, the great Swedish mycologist Elias Magnus Fries named it Agaricus portentosus. (Most of the gilled mushrooms were included initially in the genus Agaricus, which has since been slimmed down considerably as many other new general have been created to house most of its former residents.) Lucien Quélet transferred it to the genus Tricholoma in 1872, since when it has retained the name Tricholoma portentosum.

Synonyms of this Tricholoma portentosum include Agaricus portentosus Fr., Gyrophila portentosa (Fr.) Quél., and Melanoleuca portentosa (Fr.) Murill.

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 portentosum is Latin and according to my dictionary translates to portentous (an omen or sign of something important about to happen); however, some authorities state that it means prodigious, wonderful or marvelous. It is likely that Elias Fries, who selected the epithet, was referring to the appearance but rather to the flavour of this mushroom - but please see the cautionary culinary notes...

Identification guide

Cap of Tricholoma portentosum

Cap

Mouse grey or sometimes slate grey, streaked with darker grey-brown radial fibrils and often yellow highlights; initially convex, flattening but retaining an umbo; greasy when moist, becoming matt when dry; 5 to 10cm across.

Gills of Tricholoma portentosum

Gills

Broad, fairly distant, adnate; white initially but often yellowing with age.

Stem of Tricholoma portentosum

Stem

White initially, developing brownish spots with age; lined vertically with sparse fibrils; cylindrical but with a slightly swollen base; 5 to 9cm long, 6 to 12mm diameter; no ring.

 

Spores

Ellipsoidal, smooth, 5.8-7.3 x 3.5-4.5μm; inamyloid; hyaline.

Spore print

White.

Odour/taste

Odour is very slightly mealy but not generally significant; taste is mild.

Habitat & Ecological role

Ectomycorrhizal with pine trees, often in plantations on sandy soil; occasionally reported broadleaf woodland sites, particularly those containing Beech trees.

Season

Late summer and autumn, often continuing into early winter.

Similar species

Tricholoma equestre, mainly a northern species in Britain, has a yellow cap with a brown-olive central area; it has no significant odour.

Culinary Notes

Tricholoma portentosum is a good, mild-tasting edible mushroom and reported to taste even better after a slight frost; however, caution is required because it can so easily be confused with other slightly poisonous grey- or grey-brown capped species in the same genus.

Reference Sources

Fascinated by Fungi, Pat O'Reilly, 2011

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

BMS List of English Names for Fungi

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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