Gyroporus cyanescens (Bull.) Quél. - Cornflower Bolete

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

Gyroporus cyanescens, Cornflower Bolete

All parts of the Cornflower Bolete rapidly change colour if they are bruised, and in view of the scientific specific name cyanescens it probably won't come as too much of a surprise to learn that they turn blue... the vivid blue of Cornflowers, whose scientific name is Centaurea cyanus!

Until it has been handled, brushed by a passing animal, munched by a mollusc or perhaps thumped by tumbling twigs, all parts of this bolete are the colour of straw - yellow tinged with brown.

Distribution

Very rare across most of Britain and Ireland but found most often in northern parts, Gyroporus cyanescens occurs also in central and northern Europe, where it is most common in Scandinavia. The specimens pictured on this page were found mainly in Gulen, Norway, in 2014 by Arnor Gullanger. It is with Arnor's kind permission that the pictures are shown here. We took the other pictures featured on this page (including the group of three boletes shown immediately below) in central Sweden during August 2003. This bolete is also recorded in North America.

Gyroporus cyanescens, Cornflower Bolete, Sweden 2003

Taxonomic history

This bolete was named and described in 1788 by French botanist and mycologist Jean Baptiste François Pierre Bulliard, who gave it the binomial scientific name Boletus cyanescens. It was another French mycologist, Lucien Quélet, who transferred this mushroom to its present genus, which he himself established in 1886.

Synonyms of Gyroporus cyanescens include Boletus cyanescens Bull., Boletus constrictus Pers., Leccinum constrictum (Pers.) Gray, Boletus lacteus Lév., and Gyroporus lacteus (Lév.) Quél.

Etymology

The generic name Gyroporus comes ​​from the Greek Gýros, meaning round, and porus, an opening - hence round pores; while the specific epithet cyanescens means 'becoming blue'.

Like other boletes, Gyroporus cyanescens is an ectomycorrhizal fungus, which means that it forms symbiotic relationships with the root systems of trees. In the case of the Cornflower Bolete it has been found to associate with various conifers including pines and spruces as well as with some hardwoods such as birch and oak trees.

Identification guide

Cap of Gyroporus cyanescens, Cornflower Bolete

Cap

6 to 12cm across, convex but eventually flattening and usually quite regularly round rather than lobed, the caps of the Cornflower Bolete are dry and finely velvety and various shades of straw yellow, ochre or buff. The margin is often rather shaggy and in dry weather it has a tendency to split as the fruitbody ages.

The cap flesh is white and instantly turns bright blue or blue-green when cut and exposed to air.

Pores of Gyroporus cyanescens, Cornflower Bolete

Tubes and Pores

The whitish tubes of Gyroporus cyanescens turn yellow ochre with age; they terminate in round pores that turn bright blue when bruised. Pore spacing is typically 0.5mm.

The tubes are free (or very nearly so) of the stem.

Gyroporus cyanescens, Cornflower Bolete, cross-section

Stem

4 to 10cm tall and 1 to 2.5cm in diameter, stems of Gyroporus cyanescens are more or less cylindrical over most of the length but often narrowing at the apex. Hard and brittle with a dry surface coloured as the cap, the stem bears no reticulation. The interior of the stem develops cavities with age.

When cut, the flesh of the stem turns a beautiful shade of blue.

 

Spores

Ellipsoidal, smooth, 9-11 x 4.5-6μm; hyaline.

Spore print

Straw yellow.

Odour/taste

Not distinctive

Habitat & Ecological role

Mycorrhizal; often on acidic or neutral soil beneath birch and spruce trees in pine, Douglas Fir and other conifer plantations, but also on heathland, and with oaks and occasionally other hardwoods in broadleaf woodland and in parkland.

Season

Summer and autumn.

Similar species

Boletus luridus has a darker cap and orange flesh in the stem base; it also blues instantly when cut.

Suillelus satanas has a white cap and orange or red pores when mature; its flesh turns pale blue when cut and then fades back to its original pallid colour.

Mature specimen of Gyroporus cyanescens, Cornflower Bolete, Sweden

Culinary Notes

The Cornflower Bolete is generally considered edible. Although the colour change on handling it might be a deterrent to some people, its rarity, in Britain at least, is every reason for not gathering this species except where necessary for study and research purposes.

Reference Sources

Fascinated by Fungi, Pat O'Reilly 2016.

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

Roy Watling & Hills, A.E. 2005. Boletes and their allies (revised and enlarged edition), - in: Henderson, D.M., Orton, P.D. & Watling, R. [eds]. British Fungus Flora. Agarics and boleti. Vol. 1. Royal Botanic Garden, Edinburgh.

Gyroporus cyanescens, Cornflower Bolete, Norway 2014

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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