Ravenel's Bolete

Ravenel's Bolete is one of the most immediately recognisable boletes anywhere, because it is the rare case of a bolete with a well-developed universal veil. Young fruit bodies look as though they have been dusted with powdered sulphur, and as the cap expands the yellow coating splits to show a viscid orange-red to reddish-brown surface beneath.

It is the type species of Pulveroboletus, a genus in the Boletaceae named for exactly this powdery covering (from Latin pulver, dust). The veil also leaves a soft, cottony yellow ring or ring zone on the stipe, another feature almost unheard of among boletes outside Suillus.

The species commemorates Henry William Ravenel, the nineteenth-century South Carolina botanist, and it is a characteristic fungus of oak and pine woodland in the warmer parts of eastern North America, with closely related forms in eastern and southern Asia.

Cap

Convex to broadly convex, 3–10 cm across. Young caps are completely enveloped in a bright chrome to sulphur-yellow, dry and powdery to cottony universal veil. As the cap expands the veil breaks up into patches and fibrils, exposing a viscid to sticky surface coloured orange-red, brick, or reddish-brown, often brightest at the centre, with yellow veil remnants clinging to the margin.

Pores

Small and round, bright yellow when young, becoming olive-yellow to dingy brownish-yellow with age. They stain blue to blue-green where bruised, though the reaction can be modest and is sometimes slow. The tube layer is yellow and also blues in section.

Stipe

Slender to moderately stout, 4–12 cm tall, coloured yellow and covered in the same bright powdery veil material below a soft, cottony, fibrillose ring or ring zone. Above the ring the stipe is smoother and paler yellow; the base may show reddish or brownish tints, and handling leaves the fingers dusted with yellow.

Flesh and spore print

Pale yellow, sometimes with reddish tints in the stipe base, staining slowly pale blue when cut. The spore print is olive-brown, confirming its place among the boletes despite the unusual veil.

Ravenel's Bolete grows on the ground in oak, oak-pine and mixed woodland, often on sandy or well-drained soils and frequently along trail edges and open slopes. It is a mycorrhizal associate of both hardwoods, particularly oaks, and conifers, chiefly pines.

The fruiting season is summer into early autumn, coinciding with warm, humid weather. Its centre of abundance is the south-eastern and eastern United States, extending north to the Great Lakes and New England, and the species or very close relatives occur through eastern Asia, from Japan and China to South-east Asia.

The fungus forms ectomycorrhizal associations with oak and pine, its hyphae sheathing the fine roots and threading through litter and sandy soil. The presence of a well-developed universal veil is thought to protect the developing fruit body from desiccation in the hot, exposed conditions of southern oak-pine woodland, an environment where many bolete fruit bodies dry out quickly.

Fruit bodies appear singly or in small scattered groups after summer rains and last only a few days. Yellow pigment from the veil rubs off readily on litter and on the fur or feathers of animals that brush past, and the loose powdery material is easily washed into the soil, distributing spores caught within it.

Aureoboletus curtisii is also brilliant yellow, but its cap is smooth, glossy and very slimy rather than dry and powdery, and it has no veil or ring. Suillus species can carry a ring on the stipe, but they have glandular dots or smears on the stipe, sticky brown to yellow caps without a powdery yellow coating, and larger, often radially arranged pores.

Pulveroboletus relatives in Asia differ in cap colour beneath the veil and in the intensity of the blue staining. Yellow-capped members of Boletus in the broad sense lack any veil and have dry, unpowdered caps, so the presence of the loose sulphur-yellow dust and the cottony ring is decisive.