Scarlet-stemmed Bolete Identification Guide

First impression

You are usually under beech or oak on a sandy, well-drained bank, or on a mossy ride through an upland spruce plantation, when a heavy pale bolete stops you. The first impression is a mismatch. The cap is dull and unremarkable, a pale grey-buff dome that could belong to half a dozen species, but the stipe below is unmistakably red over its lower half and clear lemon-yellow at the top. That contrast between a drab cap and a vividly two-tone stipe is the species in a single sentence, and everything else confirms it.

The fruitbodies are solid and stocky, often half-buried in litter, and they are usually solitary or in scattered pairs rather than in troops.

Reading the cap

The cap is 5 to 15 cm across, occasionally to 20, hemispherical with a strongly inrolled margin when young and expanding to convex or broadly cushion-shaped. The surface is dry and finely felted, like fine suede or matt chamois, and it only becomes slightly tacky after prolonged rain. Colours run through whitish-grey, pale buff, clay, olive-buff and dingy grey-brown, often with a faint olive cast; there is no red or pink in the cap.

In dry spells the felt cracks into shallow flat plates, and in very old caps it can wear almost smooth. The margin usually overhangs the pores as a narrow sterile rim. Press the cap surface firmly with a thumbnail and note the result: it normally darkens to bluish where bruised.

The pore surface

Turn the cap and look at the underside. The pores are small, about two or three to the millimetre, circular and evenly arranged, and lemon to golden yellow, dulling to olive-yellow with age. The tubes behind them are 1 to 2 cm deep, yellow, and depressed around the top of the stipe.

Now do the bruise test properly. Press one finger firmly onto the pores and count. The colour change is prompt and emphatic: yellow to a dark blue-green within a few seconds, leaving a clean fingerprint. Slice the tube layer vertically and the cut face blues in the same way. The important point to record is that the pores are yellow and never red or orange, because that single character removes several of the closest confusions immediately.

The stipe, which is the whole point

The stipe is stout, 5 to 15 cm tall and 2 to 5 cm thick, swollen and club-shaped or barrel-shaped when young and becoming more cylindrical with age. The ground colour is bright yellow at the apex and passes over the lower half to two thirds into carmine, brick or scarlet.

Now get a lens on it. The whole stipe is covered by a raised network, fine and yellow near the top, and coarser, more elongated and red-brown lower down. You must confirm that you are looking at an actual mesh of raised ridges with sunken cells between them, and not a spray of separate dots or granules. This net-versus-dots distinction is the most valuable single observation in the entire red-stemmed bolete group, and it is worth taking your time over. Wipe off any soil, hold the lens close, and use side light.

Flesh and colour change

Cut the fruitbody vertically from cap centre to stipe base. The flesh is firm and pale lemon-yellow, sometimes whitish in the base with rose to brownish-red patches at the very bottom. On exposure it turns blue quickly and strongly through the cap and upper stipe, then fades to a duller grey-blue over the next half hour.

Check what is not there as well. There is no thin red line running along the junction between the tube layer and the cap flesh, no latex, and no gelatinous zone under the cap skin. The smell is faint and non-distinctive.

Taking the spore print

Cut the cap free of the stipe, lay it pore-surface-down on white paper, cover with a bowl to stop draughts, and leave it three to six hours or overnight. A mature cap gives a heavy deposit; a young one may give almost nothing, so choose a fully expanded fruitbody. The print is olive-brown to olive-ochre, which places it firmly in the boletes and rules out the pale-printing genera. Under the microscope the spores are smooth, subfusiform and roughly 12 to 16 by 4.5 to 6 micrometres.

Substrate and season

This is a mycorrhizal species, so record the trees within about ten metres. It partners with beech and oak on acid to neutral, sandy or gravelly, well-drained ground, and also with spruce and pine, where it can be locally abundant on mossy banks in upland plantations. Birch is a further partner on heathy soils. The season runs from mid-summer to late autumn, with a peak in late summer after warm rain. Look on the sides of woodland tracks, on sloping ground where litter is thin, and on old banks rather than in deep wet leaf mould.

Separating it from look-alikes on morphology alone

• Rooting Bolete, Caloboletus radicans: almost the same pale cap and lemon pores, but the stipe is whitish to yellow with at most a faint pink flush and no broad red zone, the network is fine and pale, and the base tapers into a distinct rooting point.
• Scarletina Bolete, Neoboletus luridiformis: a dark chestnut to olive-brown velvety cap, orange-red pores, and a yellow stipe covered in fine separate red dots with no raised mesh.
• Lurid Bolete, Suillellus luridus: orange-red pores, a tan to olive-buff cap, a coarse red network on an orange-yellow ground, and a thin red line immediately above the tubes on a vertical cut.
• Devil's Bolete, Rubroboletus satanas: a pale cap that can match closely, but blood-red pores, a squat bulbous stipe with a fine red net over yellow, and a weaker, slower blue reaction.
• Rubroboletus legaliae: cap flushed with pink, pores red.
• Butyriboletus fechtneri: grey cap and yellow pores, but the red on the stipe is a narrow band rather than a broad red lower half, and the netting is inconspicuous.
• Boletes of the classic brown-capped group with white pores: pores white then yellowish and never blueing, and a white net on a brown stipe ground.

Sequence to follow

Pale dry suede cap, then yellow pores that blue instantly, then a red lower stipe carrying a raised network, then strongly blueing yellow flesh, then an olive-brown print. If the pores are red or orange, or if the stipe is dotted rather than netted, stop and work through the alternatives above before writing anything down.