The Inkstain Bolete (Cyanoboletus pulverulentus) is a medium-sized bolete with a dry, finely velvety reddish-brown to chestnut cap and lemon-yellow pores and tubes. Its stem is yellow, often flushed with red towards the base. Every part turns blue-black almost at once when touched or cut, which makes it easy to recognise.
It grows on the ground under broadleaved trees, including hazel, beech and oak, from Jun to Oct. It is locally common and widespread in the UK, though some sources treat it as rather scarce.
Other boletes also stain blue, so check the whole combination of features. The Bay Bolete (Imleria badia) bruises more weakly and has a sticky-looking, darker brown cap. Neoboletus luridiformis has red pores. Gyroporus cyanescens is pale and bruises blue, but it has a brittle, hollowing stem. The Inkstain Bolete is reported as edible but is poor eating, and it has been shown to accumulate arsenic compounds, so it is best left uneaten. Never eat any bolete you cannot identify with certainty.
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Distribution
Locally common and widespread
Habitat
Under broadleaved trees
Etymology
Cyanoboletus combines Greek kyanos (dark blue) with Boletus (from Greek bolos, a lump), meaning a blue bolete, which fits the intense blueing of the flesh. The epithet pulverulentus is Latin for powdery or dusty, referring to the fine powdery bloom on the surface of young caps and stems.
Associates
Corylus, Fagus, Quercus
Conservation
Cap
Young caps are finely velvety and dry, becoming smoother and slightly uneven with age. The surface darkens to blue-black wherever it is handled, so older specimens are often patchy and stained.
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| Width | 5 - 8 cm |
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Pores
The pores bruise blue-black instantly when touched, so even a light brush leaves a dark mark on the yellow surface.
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Tubes
The tubes and pores are bright lemon-yellow and turn blue-black the instant they are touched. A light press leaves a dark mark within seconds.
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Flesh
The pale yellow flesh turns blue almost at once when cut or broken, quickly darkening to almost black.
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Stem
The stem is yellow with a dusty bloom, usually with red flushes, and narrows towards the base. It stains blue-black when handled, and the dark marks on old fruit bodies are often most obvious on the lower part.
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Spores
The spores are smooth and spindle-shaped, 11-16 x 4-5.5 µm, and give a deep olive spore print.
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| Size | 11-16 x 4-5.5 μm |
Microscopic Features
The cuticular hyphae of the cap surface are heavily encrusted. This is a microscopic feature and needs a prepared slide to see.
Classification
- ↳ Phylum: Basidiomycota
- ↳ Subphylum: Agaricomycotina
- ↳ Class: Agaricomycetes
- ↳ Subclass: Agaricomycetidae
- ↳ Order: Boletales
- ↳ Family: Boletaceae
- ↳ Genus: Cyanoboletus
Synonyms
- Boletus pulverulentus Opat.
- Boletus radicans sensu Rea (1922), sensu auct. mult.
- Xerocomus pulverulentus (Opat.) E.-J. Gilbert
Reference Sources
G. Kibby (2017) British Boletes with keys to species. Geoffrey Kibby.
T. Læssøe, J. H. Peterson (2019) Fungi of Temperate Europe Vol. 1. Princeton University Press.
G. Kibby (2020) Mushrooms and Toadstools of Britain & Europe Vol. 1. Geoffrey Kibby.
Genus Cyanoboletus
No other species found in this genus.
