Tricholoma scalpturatum (Fr.) Quel - Yellowing Knight

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

Tricholoma scalpturatum

A common find under broad-leaf trees, Tricholoma scalpturatum has several lookalikes in the genus Tricholoma and separating them with confidence by macroscopic characters alone requires very careful observation of cap, gill and stem features and textures; however, if you have access to a high-powered microscope then this is one of the easiest of the many so-called 'knight' species to identify, since its spores are unusually narrow (for a Tricholoma, that is).

The Yelowing Knight appears in summer and autumn, often in small scattered groups beneath mature beech, lime and oak trees but occasionally with other broadleaf trees or with pines. The specimens shown on this page were growing under Silver Birch Betula pendula in a pine copse.

Tricholoma scalpturatum with Betula pendula and pines

Distribution

This is one of the more common of several scaly-capped 'knights', and it is found throughout Britain and Ireland. This woodland mushroom is found also in many countries on mainland Europe.

Taxonomic history

When Elias Magnus Fries described this mushroom scientifically in 1838 he established it basionym, giving it the name Agaricus scalpturatus. (In the early days of fungus taxonomy, most of the gilled mushrooms were included initially in the genus Agaricus, but the vast majority have since been relocated in other newer genera to leave on the 'true mushroom' in a more manageable Agaricus genus.) It was French mycologist Lucien Quélet who in an 1872 publication established the currently-accepted scientific name as Tricholoma scalpturatum.

Synonyms of Tricholoma scalpturatum include Agaricus scalpturatus Fr., Agaricus chrysites Jungh., and Tricholoma chrysites (Jungh.) Gillet.

Etymology

The generic name Tricholoma means 'with hairs on the edge', which is true of only a minority of species in this genus. The specific epithet scalpturatum means scratched or engraved - a reference to the scales on the surface of the cap of this mushroom.

Identification guide

Cap of Tricholoma scalpturatum

Cap

4 to 8cm in diameter when fully mature, the caps are usually grey, darker in the centre and with paler margins that tend to become yellowish with age. The grey-brown fibrous surface scales are progressively denser and darker (sometimes almost black) towards the centre of the cap.

Caps are broadly convex, generally retaining a downturned margin and a very shallow umbo.

Gills and stem of Tricholoma scalpturatum

Gills

Moderately well spaced apart, the gills are adnate to emarginate, broad, white at first, yellowing with age.

Stem

Typically 10 to 20mm in diameter and 4 to 8cm long, more or less cylindrical, the stem is white or pale grey and finely fibrous, often with a faint cortina-like ring zone created by a fleeting veil. The stem yellws slightly with age.

 

Spores

Ellipsoidal, smooth, 4-6 x 3-4μm, with a hilar appendage; inamyloid.

Spore print

White.

Odour/taste

Mealy taste and odour, becoming unpleasantly rancid when old.

Habitat & Ecological role

Mycorrhizal, in broad-leaf woodland, mainly with Beech, limes and oaks;occasionally in pine woodland.

Season

Late June to early November in Britain and Ireland.

Similar species

Tricholoma sciodes is usually greyer in appearance, often with a violet tinge to its cap surface, and its gill edges develop black speckles; it occurs in oak woodland; its spores are much broader than those of Tricholoma scalpturatum.

Culinary Notes

Tricholoma scalpturatum is reported to be edible although rated no more than of moderate quality. Accurate identification is essential, however, as some members of this genus are poisonous, making it dangerous to include any but the most distinctive of of the 'knights' in mushroom dishes. Because Tricholoma species are notoriously variable in appearance, we do not include any of them in our own mushroom menus.

Reference Sources

Fascinated by Fungi, Pat O'Reilly 2016.

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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