Scarletina Bolete

The Scarletina Bolete is one of the most recognisable of the red-pored boletes, a robust woodland fungus with a sombre chestnut-brown cap set over a startling sheet of orange-red pores. It was long placed in Boletus as Boletus erythropus, but molecular work split the old catch-all genus into many smaller ones, and this species now sits in Neoboletus within the family Boletaceae.

What makes it distinctive in the field is the combination of three characters that rarely occur together: a matt, suede-textured cap that stays dark brown rather than turning olive or pink; a stipe whose yellow ground colour is covered in a dense stippling of tiny red-orange granules rather than a raised net; and a flesh that changes colour so fast that a knife cut appears blue-black almost before the blade has left the mushroom.

It is a common and often abundant fungus across temperate Europe, fruiting reliably in the same spots year after year, and it is frequently the first red-pored bolete a beginner learns to name with confidence.

Cap

Broadly convex then flattening, typically 5–20 cm across and occasionally much larger. The surface is dry and finely velvety like suede when young, becoming smoother and sometimes minutely cracked in dry weather. Colour is a deep bay to dark chestnut brown, often almost blackish-brown at the centre, sometimes with olive or rusty tones towards the margin. Touching or rubbing the cap surface leaves a blue-black smudge.

Pores

The pore surface is the headline feature: minute, round pores coloured deep orange-red to blood red across most of the fruit body, sometimes yellow-orange in a narrow band at the margin and often yellow in very young buttons before the red develops. Any pressure turns the pore surface blue-black within a second or two. Behind the pores, the tube layer itself is greenish-yellow, so a vertical cut shows a yellow-green tube layer sandwiched between the red pore mouths and the yellow cap flesh.

Stipe

Stout, club-shaped to barrel-shaped, often swollen below, 5–15 cm tall and 2–5 cm thick. The ground colour is chrome to golden yellow, densely overlaid with fine red to orange-red dots, points and granules that become denser and darker towards the base; these do not join into a raised network. The extreme base may be reddish-brown, and the basal mycelium is yellowish.

Flesh and spore print

The flesh is firm and lemon to chrome yellow, becoming deep blue then blue-black within seconds of being cut, the reaction fading over many minutes to a dull grey-blue. The spore print is olive-brown, and the spores are the smooth spindle shapes typical of the family.

The Scarletina Bolete forms ectomycorrhizal partnerships with a wide range of trees, most often beech, oak and birch among broadleaves and spruce among conifers. It shows a clear preference for acid, well-drained soils and is common in oak-birch woodland, beech hangers on sandier ground, heathy woodland edges and mossy conifer plantations.

Fruiting begins as early as June in good years and continues through to the first hard frosts of late autumn, with the main flush usually in late summer. It is widespread and often abundant throughout Europe, extending east across temperate Asia, with closely related look-alike taxa reported from North America.

This is a mycorrhizal species: the underground mycelium sheathes the fine root tips of its host tree and forms an interface through which the fungus supplies mineral nutrients and water drawn from a large soil volume, receiving photosynthetic sugars in return. Because the partnership is not narrowly host-specific, the species can colonise mixed woodland and readily follows planted trees into parkland and plantation.

Fruit bodies appear when soil moisture and temperature align, often in troops or arcs that trace the extent of the mycelial network. The tough, fleshy sporocarps are heavily used by fungus-feeding fly larvae and by small mammals and slugs, and the resulting fragmentation helps disperse spores beyond the range of simple wind fall.

The Lurid Bolete (Suillellus luridus) is the closest confusion: it has a paler olive-buff to tan cap rather than dark brown, and its stipe carries a raised, coarse red network instead of dots. Cut vertically, S. luridus also shows a thin orange-red line immediately above the tube layer, a feature absent in the Scarletina Bolete.

The Devil's Bolete (Rubroboletus satanas) is far paler, with a chalky whitish-grey cap, a squat bulbous stipe bearing a fine red net, and flesh that blues only slowly and weakly. Suillellus queletii has an almost smooth stipe without dots or net and beetroot-red flesh in the stipe base, while Rubroboletus legaliae has a pinkish-flushed cap and a netted stipe.