Leccinum variicolor Watling - Mottled Bolete

Leccinum variicolor, Mottled Bolete

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

Appearing under birch trees, usually in mossy woodlands or on wet heathland, this summer and autumn fungus has a very distinctive mottled cap. The cap colour ranges from almost white through various mid and dark browns to almost black.

The uncommon to rare whitish form of the Mottled Bolete has inverted cap coloration: the background is almost white and is variegated with a pattern of greyer spots or stripes. (An example is shown below.) If anything, this pallid form is even more difficult to identify with certainty, because other Leccinum boletes also have albino forms.

Leccinum variicolor, Mottled Bolete - white formDistribution

An occasional find in Britain and Ireland, the Mottled Bolete is also quite common throughout most of mainland Europe, from Scandinavia right down to the Mediterranean and westwards across the Iberian peninsula. Leccinum variicolor is also found in many parts of North America.

Taxonomic history

The Mottled Bolete was described in 1969 by British mycologist Roy Watling, who at that time was working in Edinburgh, Scotland.

Synonyms of Leccinum variicolor include Krombholziella variicolor (Watling) Šutara, Boletus variicolor (Watling) Hlavácek, Leccinum variicolor f. atrostellatum Lannoy & Estadès, Leccinum variicolor f. sphagnorum Lannoy & Estadès, and Leccinum variicolor var. bertauxii Lannoy & Estadès.

Etymology

Leccinum, the generic name, comes from an old Italian word meaning fungus. The specific epithet variicolor is a reference to the very variable cap colouring of this species.

Identification guide

Cap of Leccinum variicolor

Cap

Various shades of grey or dark grey-brown (a rare off-white rare form also exists) usually (but not always) variegated/mottled with a radial pattern of lighter spots or stripes, the broadly convex cap of Leccinum variicolor is finely tomentose (woolly or very finely scaly) when young but can become very much smoother as it ages. Caps range from 5 to 15cm in diameter when fully expanded.

The cap flesh is white and often turns slightly pinkish beneath the cap cuticle when it is broken or cut.

Pores of Leccinum variicolor

Tubes and pores

The small, circular tubes are broadly adnexed (but not adnate) to the stem; they are 0.7 to 1.8cm long, very pale grey to creamy-white, and terminate in pores approx. 0.5mm in diameter that are similarly coloured, often with yellowish-brown spots.

When bruised, the pores gradually turn brownish.

Stem of Leccinum variicolor

Stem

White or buff and 7 to 15cm tall, the stems of Leccinum variicolor are 2 to 3cm in diameter, tapering towards the apex. Immature specimens have barrel-shaped stems; at maturity most stems are more regular in diameter but tapering slightly towards the apex. The stem flesh is white but sometimes turns pinkish in the upper section when it is cut or broken, while near to the stem base the cut flesh turns greenish blue.

Dark brown or black scabers (woolly scales standing out from the pale background of the surface) cover the whole of the stem.

 

Spores

Fusiform, thin-walled,14-19 x 5-6.5µm, inamyloid.

Spore print

Ochraceous buff.

Note: Other microscopic characters have to be examined before a specimen can be conclusively recorded as Leccinum scabrum. Of particular significance are the caulocystidia and the hyphal structure of the pileipellis. (I'll add photomicrographs of these features one day... meanwhile I recommend the key by Geoffrey Kibby - see the References section, below.)

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. In Britain and Ireland Laccinum variicolor is mycorrhizal with birch trees (Betula spp.) in damp mossy woodlands; however, in North America this species is reported to ocvcur also with American Aspens Populus tremuloides.

Season

July to November in Britain and Ireland.

Similar species

Leccinum versipelle has a much more orange cap; it bruises blue-green in the stem base.

Leccinum scabrum is also very variable in cap colour, although usually a lighter brown than the Mottled Bolete; its stem flesh does not turn blue or blue green when cut or broken.

Leccinum variicolor, Mottled Bolete - New Forest

Culinary Notes

Leccinum variicolor is generally considered to be a 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). Alternatively, use Mottled Boletes to make up the required quantity if you do not have sufficient Ceps.

Reference Sources

Pat O'Reilly, Fascinated by Fungi, 2011.

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.

The picture shown above was taken in England by David Kelly, with whose kind permission it is shown here.

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.

Other web pages on this species

Machiel Noordeloos (Netherlands)

Roger Phillips (UK)

Marek Snowarski (Poland)

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