Boletus rubroflammeus

The shape of the cap of B. rubroflammeus is convex to broadly convex, and reaches a diameter of 6–12 cm (2.4–4.7 in). The margin of the cap extends slightly beyond the tubes. The cap surface is dry and initially appears appressed-fibrillose (with fibrils pressed down flat against the surface) or has a matted grayish tomentum, but later the hairs slough off and the matted tomentum is present only along the cap margin. In maturity, the center of the caps develop slight cracks. The cap is a deep vinaceous-red color that remains constant throughout the life of the fruit bodies. The flesh is thick, soft, and yellow. Its taste is mild, and it has no distinct odor. On the underside of the cap, the spore-bearing surface comprises vertically arranged minute tubes with pore-like openings. The tubes are yellow, 1–2 cm (0.4–0.8 in) deep, initially adnate (fused) to the stem, but later becoming free from attachment (or nearly so). Individual pores are round and small (about 2 per mm), while the overall pore surface is uneven or pitted. Its color is initially deep red, but fades slightly in maturity; the pore surface quickly turns blue with injury. The stem is 6–8 cm (2.4–3.1 in) long, 1–2 cm (0.4–0.8 in) thick, solid (i.e., not hollow), and equal in width throughout to club-shaped. Inside, it is yellowish with reddish streaks. …

Boletus rubroflammeus is a mycorrhizal species, and its fruit bodies grow scattered or in groups on the ground under hardwood trees. The fungus fruits in summer and autumn months, and tends to appear after hot weather and heavy rains. Known only from North America, its range extends from New England south to Tennessee, and west to Michigan. It has also been recorded from Mexico.