Lurid Bolete Identification Guide

Where You Are Standing

Red-pored boletes concentrate in a very specific setting, and knowing it halves the work. You are on chalk or limestone, in warm broadleaf woodland or old parkland, along a track edge or a sunny woodland margin under oak, beech, lime or hornbeam. The month is anywhere from June to October, with this species often the first of its group to appear.

What you see is a stout, heavy fungus with a dull olive-brown cap sitting low over a swollen stem, and, once you tip it, a shock of orange-red where you expected pores. The instinct is to name it on the red pores alone. Do not: several species share them, and the actual identification lives on the stem surface and in a thin line of colour inside the cap.

The Cap

Diameter is typically 6 to 15 cm and occasionally 20 cm on old parkland material. The shape moves from hemispherical, almost bun-like, through convex to broadly flattened, and the margin stays inrolled for a long time so that young fruit bodies look tightly tucked.

The surface is dry and finely velvety, like suede or chamois, becoming slightly tacky in wet weather but never truly slimy. Colour is variable within a narrow, muted range: olive-brown, tan, ochre-brown, greyish-buff, sometimes with a warm russet or rosy flush in the middle or towards the margin. It is a dull cap, and its dullness is part of the picture.

Press the cap firmly with a thumb. It bruises blue-black at the point of pressure within seconds, and grazes made by slug damage or transport show the same dark blue staining.

Pores and Tubes

The pore mouths are orange-red to blood-red over most of the surface, usually more orange near the margin and in very young buttons, and they are small and round. They blacken to deep blue on the lightest touch, so a fingerprint-shaped blue mark appears wherever you have handled it.

Cut vertically through the cap and look at the layer behind the pores. The tubes themselves are yellow to olive-yellow, contrasting with the red mouths, and they also turn blue on exposure. That colour discontinuity, red mouths on yellow tubes, is worth registering because a few relatives have red pigment running further into the tube layer. The tubes are depressed around the top of the stem.

The Stem: Network, Not Dots

This is the decisive part of the identification, and it needs a hand lens.

The stem is 8 to 15 cm tall and 2 to 5 cm thick, club-shaped and noticeably swollen in the lower half, solid and firm. The ground colour is yellow at the apex, passing through orange to a red-brown or dark brick tone at the base. Over that ground runs a raised, three-dimensional mesh: a reticulum, with the ridges coloured red to orange-red, the meshes often elongated vertically, and the network usually covering most or all of the stem length.

The test to run is network versus dots. Put a lens on the upper third of the stem. If you see raised ridges joining into a continuous net, like the wire of a fence, you are looking at Suillellus luridus. If instead you see thousands of separate red granules or points, unconnected, giving a stippled or scurfy look, you are in a different species. This one distinction resolves the great majority of red-pored bolete records.

The base is often deep reddish-brown and the attached mycelium is yellowish.

Flesh and Colour Change

Slice the whole fruit body cleanly in half from the top of the cap to the bottom of the stem, and watch the cut face rather than glancing at it.

The flesh is pale yellow through cap and stem, deepening to reddish or beetroot tones in the lower stem in some collections. Exposure produces a strong and immediate blue: within a few seconds the cut surface goes deep blue to blue-black, then over the following minutes it settles to a duller blue-grey and eventually fades towards greyish.

The character to catch is a narrow band of reddish-brown flesh lying immediately above the tube layer, at the junction between cap flesh and tubes. It is only a millimetre or two deep and it is visible for a very short time before the general blueing swamps the whole face, so cut and look at once. That line, combined with the red-netted stem, is the classic confirmation of this species.

The smell is faint and slightly acid or fruity, and there is no latex.

Taking the Spore Print

Boletes deposit slowly and need patience. Cut the stem off flush, lay the cap pore-surface downward on white paper, cover it with a bowl to keep it humid, and leave it for six to twelve hours; overnight is normal.

The print is olive-brown to snuff-brown, a colour shared across the group and therefore useful for confirming that you are dealing with a bolete of this sort rather than for separating species. Expect the cap to leave a blue stain on the paper where the flesh touched it; read the print from the deposit further out, not from the contact zone. Under the microscope the spores are smooth and spindle-shaped.

Substrate and Season

Suillellus luridus is ectomycorrhizal, forming partnerships with broadleaf trees, principally oak, beech, lime, hornbeam and sweet chestnut. It has a marked preference for calcareous, well-drained, warm soils, which is why it turns up so consistently in chalk beechwoods, limestone oakwoods, old churchyards, avenues and parkland with veteran trees, and is scarce or absent on acid sands.

Season is June to October, often starting earlier than the rest of the group. Fruit bodies come singly or in small scattered groups along the drip line of the host tree, and are frequently found on track edges where the soil is compacted and warm.

Separating the Close Look-Alikes

Neoboletus luridiformis, formerly Boletus erythropus, is the commonest confusion. Its cap is darker brown and more velvety, its pores are a deeper red, its flesh blues even faster and more intensely, and, critically, the stem is covered in fine separate red dots and granules with no network at all. Lens on the stem, and the question is answered.

Rubroboletus satanas is squat and very broad, with a pale whitish-grey to dirty cream cap that is quite unlike the olive-brown of luridus, a hugely bulbous stem with a fine red net over a yellow ground, red pores, and flesh that blues only weakly and patchily. Older fruit bodies develop a strong unpleasant smell.

Rubroboletus legaliae and its relatives show pinkish tones in the cap, a red network, and again weaker blueing than luridus.

Suillellus queletii has a smooth stem with no true network, at most a fine granulation, an orange-brown to brick cap, and a deep beetroot-red colour in the flesh of the stem base. Stem ornamentation and base colour separate it.

Suillellus mendax carries a network only in the upper part of the stem, often shows reddish tints at the cap margin, and has scattered red-brown flecks in the base flesh; it is largely a southern species of chestnut and oak.

Caloboletus radicans has a pale whitish to grey cap, lemon-yellow pores rather than red, a yellow network, blueing flesh, and a whitish rooting base.

Boletus edulis and its allies carry a white network on a pale stem, have white then yellow-olive pores, and do not blue at all.

The Sequence to Follow

Pores red, cap dull olive-brown and velvety, stem netted in red on yellow, flesh blueing instantly, thin red-brown line above the tubes, broadleaf trees on lime-rich soil. Photograph the stem surface close up and the freshly cut section within ten seconds of cutting, and the record will stand.