Devil's bolete

Description

The devil's bolete is a massive, heavy bolete with a greyish, suede-like cap that can be more than 20 cm across. Most characteristic are the tubes with red pores (yellow-orange in young ones) and the thick, barrel-shaped stem, yellow at the top and carmine-red lower down, covered with a net. The flesh slowly turns blue when cut, and in older fruiting bodies it smells unpleasant, like carrion.

It grows from July to September in warm deciduous forests, especially under oaks and beeches, on calcareous soils. In Poland it is very rare and dying out, and is therefore under strict species protection.

An inexperienced collector may confuse it with boletes, especially when the fruiting body is young. All boletes with red pores and flesh that turns blue should be treated as suspicious and not collected. If you are not certain of the species, do not collect or eat it.

Identification features

Cap

Diameter usually 6–30 cm (exceptionally up to 40–50 cm), probably the largest bolete in Europe. Hemispherical with an inrolled margin when young, then cushion-shaped and flattened, thick, compact. Colour greyish-white, silvery-white or buff, olive, ochre, yellowish or brownish tinged in older fruiting bodies; brown-ochre when pressed. Skin matt, dry or suede-like (finely felty), smooth with age, may be slightly sticky in wet weather; tightly attached to the flesh, not peelable.

Hymenophore (underside of the cap)

Tubes free or slightly attached, up to about 3 mm long, at first yellowish or greenish-yellow, then blood-red, brown-olive in old ones; turning blue when damaged. Pores round, at first yellow to orange, then reddening from the stem side, at full maturity carmine or purple-red, olive in very old ones; turning blue immediately when touched.

Stem

Height 5–15 cm (exceptionally up to 20–25 cm), thickness 3–8 cm, solid, massive, at first spherical or cylindrical, then barrel-shaped with a distinctly bulbous base, often wider than long. Colour: yellow to orange under the cap, pinkish-red lower down, carmine to purple-red towards the base. Covered with a fine yellowish to reddish net with hexagonal meshes, sometimes only in the upper half of the stem.

Flesh

Whitish, thick, spongy, sometimes yellow or straw-coloured in young fruiting bodies, may be reddish at the base of the stem. Slowly turns pale blue when cut, more intensely around the top of the stem and above the tubes. Smell weak, pleasant, musky in young fruiting bodies; distinctly unpleasant, carrion-like in older ones. Taste mild, described as nutty in young specimens; it must not be tasted; do not taste the flesh of this or any suspicious mushroom.

Spore print and spores

Spore print olive (olive-green). Spores smooth, spindle-shaped to ellipsoid. Dimensions about 10–16 × 4.5–7.5 µm (descriptions give inconsistent figures).

Habitat and distribution

Ecology. Terrestrial mycorrhizal fungus (ectomycorrhiza), mainly with oak and sweet chestnut, also with hornbeam, beech and lime. Grows in warm deciduous and mixed forests, prefers calcareous soils.

Distribution. Europe, mainly its warmer parts; rare everywhere. In Poland very rare and dying out (Red List 2006: E — endangered), with isolated sites known in, among others, the Kaczawskie Mountains and the Kraków-Częstochowa Upland, and others also described, e.g. in Ponidzie. In Poland it is under strict species protection. Old reports from North America concern another species (Rubroboletus eastwoodiae).

Fruiting. From July to September (summer and early autumn).

What can it be confused with?

• Rubroboletus rhodoxanthus (purple-red bolete) — Also rare; pinkish tinge of the cap, stem cylindrical or club-shaped with a dense, well-developed net, lemon-yellow flesh turning blue only in the cap; grows mainly on acidic soils.
• Caloboletus calopus (bitter beech bolete) — More common, usually associated with conifers; pores stay yellow even in old specimens, stem more slender, flesh bitter.
• Suillellus rubrosanguineus (spruce-fir blood bolete) — Grows in coniferous forests, under spruce or fir; pinkish tinge of the cap, smaller spores.
• Rubroboletus legaliae and Rubroboletus pulchrotinctus — R. legaliae: prefers acidic soil, pinkish tinge of the cap, flesh turns blue over a wider area; R. pulchrotinctus: rare, Mediterranean, pores stay yellow or orange, stem without deep red.
• Boletus edulis (porcino) and Boletus reticulatus (summer bolete) — Species sometimes confused. Boletes do not have red pores or a red, netted stem and do not turn blue. Detailed differences: no data.

Never rely on a single feature. If you are not sure — do not pick it; show the mushroom to a qualified mushroom expert.

Interesting facts

• The epithet satanas was given by Lenz in 1831; he knew of reports of bad reactions after eating the mushroom and himself reportedly felt unwell from unexplained "fumes" while describing the species.
• It is one of the largest boletes in Europe: cap usually up to 30 cm, exceptionally up to 50 cm across.
• The name "borowik szatański" was given in 1939 by Alina Skirgiełło; after the move to the genus Rubroboletus the name krwistoborowik szatański was recommended in 2021.
• Old reports from the USA actually concerned the closely related Rubroboletus eastwoodiae.