Suillus serotinus is a species of bolete fungus found in eastern North America. Originally described as a species of Boletus by American botanist Charles Christopher Frost in 1874, it was transferred to Suillus in 1996. The bolete has a dark red brown and sticky cap up to 12 cm (4.7 in) in diameter. The pore surface is initially white before turning reddish brown in age; the angular pores number from 1 to 3 per millimeter. Mushroom flesh slowly stains bluish after injury, later becoming purplish gray then finally reddish brown. The fungus grows in a mycorrhizal association with larch and fruits on the ground scattered or in groups. The spore print is purplish brown; spores are oblong to ellipsoid, smooth, and measure 8–12 by 4–5 µm. The fruit bodies are edible, but lack any distinctive tas