Red-pored Bolete

Colored various shades of olive- to reddish-brown, the cap may sometimes reach 25 centimeters (10 in) in diameter and is convex in shape before flattening at maturity. The cap surface may be smooth or velvety when young, but may be scaled in older specimens; the margin of the cap is curved inwards in young specimens but rolls out and flattens as it matures. The cap may reach a thickness of 3 to 4 cm (1.2 to 1.6 in) when mature. The adnate (attached squarely to the stem) poroid surface is bright red to dark red or red-brown and bruise dark blue or black; there are 2 to 3 pores per mm in young specimens, and in maturity they expand to about 1 or 2 per mm. In cross section, the tubes and flesh are yellow. The tubes are between 0.5 to 1.5 cm (0.2 to 0.6 in) long, while the angular pores are up to 1 mm in diameter; pores can range in color from dark red in young specimens to reddish brown in age. The pores will stain a blue color when cut or bruised. The solid, firm stem is 7–20 cm (3–8 in) long and thick—up to 10 cm (4 in) in diameter, at the base before tapering to 2–5 cm (1–2 in) at the top. It is yellow or yellow-brown in color and bears a network of red reticulations on the upper 2/3 of its length. The spore print is olive-brown. The taste of the flesh is reportedly mild, and the odor indistinct, or "slightly fragrant".

Microscopic characters. …

Rubroboletus pulcherrimus is found in western North America, from New Mexico and California to Washington, and may feasibly occur in British Columbia, Canada. One source notes it grows at low altitudes in the Cascade Range and Olympic Mountains; another claims it grows at high elevations, over 5,000 ft (1,500 m). Fruiting in autumn, it grows singly or in groups (although another source claims "never in groups") in humus in mixed woodlands. In the original publication describing the species, Thiers and Halling note that it is associated with forests containing tanbark oaks (Lithocarpus densiflora), Douglas-fir (Pseudotsuga menziesii), and grand fir (Abies grandis). Smith and Weber mention increased fruitings after warm heavy fall rains following a humid summer.