Leccinum cyaneobasileucum Lannoy & Estadès - Greyshank Bolete

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Boletales - Family: Boletaceae

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

Appearing under birch trees mostly on acid soil, this common summer and autumn bolete is one that even inexperienced fungi foragers are unlikely to confuse with any of the dangerously poisonous gilled mushrooms.

Leccinum cyaneobasileucum is similar in appearance to and often misidentified as the Brown Birch Bolete Leccinum scabrum - and indeed until 1991 these two species were not formally recognised as separate.

Leccinum cyaneobasileucum is one of the most common and widespread of the scaberstalk boletes, but that doesn't mean that its identification is easy. Colours change with age, and most Leccinum boletes change shape as well as colour depending on how wet they are. As with all members of this deceptively difficult group, confident identification of Leccinum cyaneobasileucum requires study of both macroscopic and microscopic features.

Cap colour is not a key determining feature of this scaberstalk mushroom: it ranges from very pale grey (almost white) through various shades of greyish brown to very dark grey (almost black); however, the general grey tinge and the woolly stem surface, usually bluish towards the slightly swollen base give it a distinctive 'jizz'.

Distribution

Probably far more common in Britain (particularly southern England) and Ireland than its entry in the Fungal Records Database of Britain and Ireland suggests, this boletoid mushroom is also found throughout much of mainland Europe as far north as Denmark. The white form of Leccinum brunneogriseolum shown on the left was photographed in central France.

Taxonomic history

The white form of this bolete was described in 1991 by Lannoy & Estadès before they recorded brown form, and because initially they gave the white form the specific name Leccinum cyaneobasileucum (reserving Leccinum brunneogriseolum for the more common brown form), under the rules of the international naming convention the binomial scientific name Leccinum cyaneobasileucum takes precedence

Leccinum brunneogriseolum Lannoy & Estadès, and Leccinum brunneogriseolum f. chlorinum Lannoy & Estadès are Synonyms of Leccinum cyaneobasileucum.

Etymology

Leccinum, the generic name, comes from an old Italian word meaning fungus. The specific epithet cyaneobasileucum is a reference to the bluing at the stem base when it is cut through or otherwise damaged.

Identification guide

	Cap Various shades of grey brown (and there is a very rare albino form), the cap of Leccinum cyaneobasileucum is usually circular and only occasionally slightly misshapen with its margin somewhat wavy (but rarely as irregular as many large specimens of its lookalike Leccinum scabrum). The cap surface is very finely tomentose (like velvet), and the margin of the pellicle overhangs the tubes very slightly in young fruitbodies. Initially hemispherical, caps, which become to convex but do not flatten completely, range from 4 to 8cm in diameter when fully developed.
	Tubes The circular tubes, typically 0.5mm in diameter, are broadly adnate to the stem; they are 1 to 1.5cm long, off-white with a grey-brown tinge.
	Pores The tubes terminate in pores that are similarly coloured. When bruised, the pores do not undergo a rapid colour change but gradually turn slightly browner.
	Stem Very pale grey to greyish brown and covered with concolorous scales that turn greyer with age, the stems of Leccinum cyaneobasileucum range from 1 to 2.5cm in diameter and are usually 7 to 14cm tall. Immature specimens often have barrel-shaped stems; at maturity stems become more regular in diameter, usually slightly clavate and tapering in towards the apex.
	The stem flesh is white but sometimes turns slightly pink near the apex when it is cut or broken and always blues (although often only in a very limited region) at the base. The exterior of the stem base usually has a blue tinge that is most noticeable where slugs, snails or bugs have damaged its surface - a helpful identifying feature.
	Basidia Mainly 4-spored but usually with some 2-spored basidia. Show larger image Basidium of Leccinum cyaneobasileucum  X
	Spores Fusiform, 13-19 x 4-6.5 µm. Show larger image Spores of Leccinum cyaneobasileucum  X  Spore print Pale brown.   Note: Other microscopic characters have to be examined before a specimen can be conclusively recorded as Leccinum cyaneobasileucum. Of particular significance are the caulocystidia and the hyphal structure of the pileipellis (see below).
	Pileipellis The pileipellis (cap cuticle) usually has numerous cylindrocysts (short, disarticulating hyphal cells, as seen on the left). Show larger image Pileipellis of Leccinum cyaneobasileucum  X
Odour/taste	The faint smell and taste are pleasant but not particularly distinctive.
Habitat & Ecological role	All Leccinum species are ectomycorrhizal, and most are found only with one tree genus. Leccinum cyaneobasileucum is mycorrhizal only with birch trees (Betula spp.) and in Britain and Ireland this mushroom is found nearly always beneath Silver Birch Betula pendula or Downy Birch Betula pubescens.
Season	July to November in Britain and Ireland.
Similar species	Leccinum scabrum does not blue in the stem base when cut or broken; it is often rather larger than Leccinum cyaneobasileucum and there are significant differences in microscopic characters that separate these two superficially very similar boletes. Leccinum versipelle has a much more orange cap and it bruises blue-green in the stem base.

Culinary Notes

Leccinum cyaneobasileucum is generally considered to be a fairly good edible mushroom and can be used in recipes that call for Ceps Boletus edulis (although in both flavour and texture a Cep is superior) or to make up the required quantity if you do not have sufficient Ceps.

Reference Sources

Pat O'Reilly, Fascinated by Fungi, 2016.

Henk C. den Bakker, Barbara Gravendeel & Thomas W. Kuyper (2004). An ITS phylogeny of Leccinum and an analysis of the evolution of minisatellite-like sequences within ITS1; Mycologia, 96(1), 2004, pp. 102-118.

British Boletes, with keys to species, Geoffrey Kibby (self published) 3rd Edition 2012.

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.

Acknowledgements

This page includes pictures kindly contributed by David Kelly.

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