Violet-gray Bolete

Few boletes are as richly coloured when fresh as the Violet-gray Bolete. Young fruitbodies emerge a saturated purple-violet across both cap and stipe, contrasting sharply with a chalk-white pore surface. As the mushroom ages the violet drains toward lead-grey, grey-brown and finally dull brown, so a single troop may show the full colour sequence at once.

It belongs to Tylopilus, the pink-spored bolete genus, and shares with its relatives white pores that flush pink at maturity and flesh that does not turn blue. Within that genus it is distinguished by its violet pigments and its nearly smooth stipe.

The species is a characteristic summer mushroom of eastern North American oak woods and is often abundant in the same seasons and sites as the Bitter Bolete and the Lilac-brown Bolete, making those three a useful comparative set for learning the genus.

Cap

The cap is 5-15 cm across, convex to broadly convex and eventually flattened. The surface is dry and matt, minutely velvety at first, sometimes becoming finely wrinkled or cracked in age. Fresh colour is a deep violet to purple-grey, fading unevenly through lilac-grey and pinkish-brown to dull brown, with older caps often retaining violet only near the margin.

Pores

The pore surface is white when young, gradually turning pale pink and finally a definite flesh-pink. Pores are small and round, and the tubes are depressed around the stipe. Bruising leaves brownish rather than blue stains.

Stipe

The stipe is 5-12 cm long, 1-3 cm thick, equal to slightly club-shaped, and coloured violet to pale purple over most of its length, often whitish at the extreme base. The surface is smooth or at most faintly and finely reticulate near the very top, never carrying the coarse dark net of the Bitter Bolete.

Flesh & spore print

The flesh is firm and white and remains white when cut, occasionally showing a faint pinkish or greyish tint but never blueing. The spore print is pinkish-brown.

This bolete grows on soil in deciduous and mixed forest dominated by oaks, and is also found under beech and in oak-pine mixtures. It appears singly, scattered or in small groups, often on well-drained slopes, along shaded woodland roads, and beneath heavy oak leaf litter.

The fruiting season is from early summer to early autumn, chiefly July through September, following warm rains. Its range is eastern North America, from southern Ontario and New England south to the Gulf states and west to the Ozarks, with related violet-capped species described from eastern Asia.

Tylopilus plumbeoviolaceus is ectomycorrhizal with oaks and other hardwoods. Its mycelium envelops the tree's fine root tips in a fungal mantle, then threads between the outer cortical cells to form the exchange interface, supplying the tree with water and soil nutrients in return for carbohydrates.

Because the partnership is obligate for the fungus, its distribution follows mature oak stands closely, and it can be a useful indicator of long-established hardwood woodland. Fruitbodies decay rapidly once mature, feeding invertebrate larvae and small mammals and cycling nutrients back into the litter layer.

The Lilac-brown Bolete (Sutorius eximius, formerly Tylopilus eximius) has a similar dark purplish-brown cap but a pore surface that is purple-grey from the outset rather than white, and a stipe densely covered in fine dark purplish dots and scurf. Tylopilus rubrobrunneus is generally larger with a purple-brown to reddish-brown cap and a pale buff, non-violet stipe.

The Bitter Bolete (Tylopilus felleus) shares the white-to-pink pores and pink spore print but has a plain brown cap and a coarse dark brown network on a pale stipe. Boletus violaceofuscus also has a violet cap, but its pores are white then yellow, its stipe carries a white net, and its spore print is olive-brown.