Lurid Bolete
Suillellus luridus
Also called lurid boletus
A red-pored bolete of limy soils recognised by the coarse red network covering its stipe and by the thin orange-red line revealed just above the tubes when the fruit body is cut lengthways.
Overview
The Lurid Bolete is a substantial, warm-toned bolete of calcareous woodland and old parkland, and one of the best known members of the genus Suillellus, a segregate of the old Boletus that gathers the red-pored, blue-staining species with reticulate stipes. Its name refers to the dull, smoky olive-yellow wash on the cap rather than to anything about the mushroom's behaviour.
It is distinctive because it combines a rather nondescript cap with two very specific structural characters: a raised red mesh over the stipe and an internal band of orange-red tissue lying between the cap flesh and the tube layer, sometimes called Bataille's line. Together with the instant blue reaction of the flesh, these give a reliable field identity.
Within the wider Boletaceae, Suillellus sits close to Neoboletus and Rubroboletus, and the three genera collectively account for most of the stout red-pored boletes of temperate woodland.
How to identify it
Cap
Hemispherical at first, expanding to broadly convex and finally almost flat, 6–20 cm across. The surface is dry, matt and finely felted, becoming slightly greasy in wet weather. Colour varies from olive-buff and clay-brown to tan, ochre or dull orange-brown, often paler and yellower at the margin, and it bruises blue-black where handled.
Pores
Small and round, orange-red to brick or rusty red over most of the surface, typically yellow to yellow-orange in a zone near the cap margin and in very young specimens. Bruising to dark blue is immediate. The tube layer behind the pores is yellow to olive-yellow.
Stipe
Stout and often swollen or club-shaped, 8–15 cm tall. Over a yellow to orange-yellow ground it carries a conspicuous, raised, coarse network of red to reddish-brown ridges, elongated and coarser towards the base; near the apex the mesh may be finer and yellower. The base is often reddish and the basal mycelium yellowish.
Flesh and spore print
Firm and pale yellow, turning deep blue within seconds of cutting, the colour later fading. A vertical section through the cap and tubes reveals a narrow but usually distinct orange-red to wine-red line immediately above the tube layer, best seen before the blue reaction floods the section. The spore print is olive-brown.
Where and when it grows
This species is strongly associated with base-rich and calcareous soils. It forms mycorrhizas most often with beech, oak, lime and hornbeam, and is a familiar find in chalk and limestone beechwoods, on woodland rides and banks, and under mature planted broadleaves in parks, churchyards and avenues.
Fruiting runs from midsummer into autumn, peaking in warm, damp late-summer weather. It is widespread across Europe, extending into North Africa and western Asia, and is commonest in the warmer, drier lowlands rather than in upland conifer country.
Ecological role
Suillellus luridus is ectomycorrhizal, wrapping the short roots of its broadleaved partners in a fungal sheath and extending hyphae into the surrounding soil to scavenge phosphorus, nitrogen and water. On thin chalk soils, where nutrients are locked in mineral form and drainage is sharp, such partnerships are particularly important to tree performance.
Because its hosts are long-lived, colonies can persist for decades, and fruit bodies often reappear in the same short stretch of woodland bank season after season. The fleshy sporocarps are quickly colonised by fly larvae, and older specimens frequently show tunnelled stipes and collapsed tube layers.
Similar species
The Scarletina Bolete (Neoboletus luridiformis) has a much darker bay-brown cap and a stipe covered in isolated red dots rather than a raised net, and it lacks the orange-red line above the tubes. The Devil's Bolete (Rubroboletus satanas) is far paler, with a chalk-white to pale grey cap and a squat, bulbous stipe with a fine red net, and its flesh blues slowly and weakly rather than instantly.
Suillellus queletii has a smooth, unnetted stipe and deep beetroot-red flesh at the very base, while Suillellus mendax is similar to the Lurid Bolete but tends to have a stipe net restricted to the upper part with red dots below, and reddish tints in the stipe flesh. Rubroboletus legaliae shows pink flushes on the cap and a paler, chunkier build.