Black Velvet Bolete
Tylopilus alboater
Also called black velvet tylopilus, white-black bolete
A dramatic bolete with a velvety black cap and stipe over a white pore surface. Cut flesh flushes pink then slowly turns grey to black.
Overview
The Black Velvet Bolete is one of the darkest boletes in eastern North American woodlands, an almost charcoal-black mushroom whose dry cap surface has the nap of fine velvet or suede. Against that darkness the chalk-white pore surface of young specimens is startling.
It is a member of Tylopilus, sharing the genus hallmark of a pinkish-brown spore print and pores that pass from white to pink. Where it departs from its relatives is in its dramatic two-stage colour change: cut or bruised flesh first flushes rose-pink, then over several minutes darkens through grey to blackish.
Sturdy and firm-fleshed, it lasts longer in the field than most boletes and holds its shape well, so specimens can often be found in good condition days after emerging.
How to identify it
Cap
The cap is 5-15 cm across, convex to broadly convex, with a dry surface densely covered in a fine velvety to suede-like tomentum. The colour is sooty black to blackish-brown or dark grey, sometimes developing a faint bloom, and often cracking into a fine mosaic in dry weather to reveal paler flesh beneath.
Pores
The pore surface is white to pale grey when young, ageing pinkish-grey. Pores are small and round, and the tubes are depressed around the stipe. Pressed or bruised, the surface stains pink and then blackens, which makes handled specimens conspicuously marked.
Stipe
The stipe is 4-10 cm long and 1.5-3.5 cm thick, equal or slightly tapering at the base, and coloured like the cap, blackish to dark grey with the same fine velvety covering. It is not reticulate, though the surface may be faintly ridged near the apex; the extreme base is often paler.
Flesh & spore print
The firm white flesh is the best confirming character: sliced, it turns rose-pink within a minute, then slowly greys and finally blackens. The spore print is pinkish-brown.
Where and when it grows
The Black Velvet Bolete grows on soil in deciduous woodland, strongly associated with oaks and also occurring under beech and in oak-hickory stands. It fruits singly or in scattered groups on leaf-littered slopes, wooded banks and shaded trail sides, sometimes in loose clusters of two or three.
It is a warm-season species, fruiting from early summer to early autumn, typically June through September, and responding quickly to summer thunderstorms. Its range covers eastern North America from New England and the Great Lakes south through the Appalachians to the Gulf coastal plain.
Ecological role
This species is ectomycorrhizal with oaks and related hardwoods. Fungal hyphae wrap the tree's short roots in a mantle and grow inward between root cells, forming the exchange network through which soil nutrients move to the tree and sugars move to the fungus.
The dark pigments in the cap and stipe are thought to help the fruitbody withstand desiccation and sunlight in the relatively open, warm conditions where it often fruits, and the unusually firm flesh resists insect damage longer than most boletes. As the fruitbody eventually collapses, its nutrients return to the litter layer, while the mycelium persists among the host roots year-round.
Similar species
Tylopilus atronicotianus, the false black velvet bolete, is very similar but has a duller brownish-black cap, less pronounced velvet, and a weaker or absent pink stage in the flesh reaction. Dark forms of the Gray Bolete (Retiboletus griseus) can approach it in cap colour but have a whitish stipe with a coarse dark raised net, white flesh that does not flush pink, and an olive-brown spore print.
Porphyrellus species share a dark cap and pinkish-brown spores but have brown, non-velvety caps and flesh that reacts blue-green then reddish. Blackening Russula and Lactarius species are gilled rather than pored, which rules them out immediately.