Red-mouth Bolete

The Red-mouth Bolete is the classic red-pored, instantly blue-staining bolete of hardwood and mixed forests in eastern North America, filling much the same ecological and visual role there that Neoboletus luridiformis does in Europe. Its common name comes from the deep red pore mouths, which contrast sharply with the more sober brown of the cap.

Described originally in Boletus, it now sits in Suillellus within the Boletaceae. It belongs to a notoriously variable complex, and several regional segregates have been named around it, so field collections often key out as Suillellus subvelutipes in the broad sense rather than to a narrowly defined species.

The single most useful field character is the stipe base, which is clothed in coarse, dark red to blackish-red hairs or strigose fibres, a texture reflected in the epithet subvelutipes, meaning somewhat velvet-footed.

Cap

Convex to broadly convex, 5–15 cm across. The surface is dry and finely velvety when fresh, sometimes becoming smooth or slightly cracked in age. Colours range widely through tan, cinnamon, ochre-brown and reddish-brown, occasionally with olive or paler yellow zones, and the surface bruises blue-black where handled.

Pores

Small and round, deep red to dark brick or maroon-red across most of the surface, often with a narrower orange or yellowish band at the cap margin and yellow in the youngest specimens. The blue-staining reaction on bruising is immediate and intense. The tube layer behind the pores is yellow to olive-yellow and also blues quickly.

Stipe

Equal to slightly swollen, 5–12 cm tall, yellow at the apex and increasingly reddish or reddish-brown downwards, dotted or finely punctate with red granules but without a raised network. The base is characteristically covered in coarse, dark red to almost blackish strigose hairs, and the basal mycelium is yellowish.

Flesh and spore print

Pale to bright yellow, sometimes reddish in the stipe base, changing instantly to deep blue on cutting before slowly fading. The spore print is olive-brown.

This is a mycorrhizal species of mixed forest, associating with oaks, beech, birch and hemlock and often abundant where hardwoods and conifers intergrade. It grows scattered or in small groups on soil among leaf litter, and is frequent along wooded trails and slopes.

The main fruiting period runs from late June through September, peaking after summer thunderstorms. Its range covers eastern North America from the Canadian Maritimes and Great Lakes south to the Gulf states, with similar or identical fungi reported from eastern Asia.

Suillellus subvelutipes forms ectomycorrhizas, encasing the fine root tips of its tree partners in a hyphal mantle and extending a network of absorptive hyphae through the litter and upper mineral soil. Broad host tolerance, spanning both oak and hemlock, allows it to persist through the shifting composition of eastern deciduous and transition forests.

The substantial fleshy fruit bodies are quickly exploited by fly larvae, beetles and small mammals, and decompose rapidly once colonised, returning nutrients directly to the litter layer that the mycelium occupies.

The Two-coloured Bolete (Baorangia bicolor) has a rosy red to brick cap and, decisively, yellow pores that stain blue slowly and patchily, not red pores. Neoboletus and Suillellus species in the same woods generally differ in stipe ornamentation: the Lurid Bolete (Suillellus luridus) carries a raised red network, whereas the Red-mouth Bolete has dots and coarse basal hairs only.

Rubroboletus frostii is separated by its sticky, deeply red, strongly and coarsely reticulate stipe and shiny blood-red cap, while Suillellus hypocarycinus and other members of the complex differ in subtler cap colour and in the extent of red on the stipe. Checking the stipe base for coarse dark hairs is the quickest way to place a collection in this group.