Red-stipe bolete

Appearance

Fruit bodies are robust, with caps up to 18 cm in diameter, atop thick stipes 5–12 cm long. Mushrooms are non-toxic, but is so bitter as to be inedible. The mushroom flesh has a very strong bluing reaction when cut or damaged. and forms mycorrhizal relationships, primarily with conifers. It can be differentiated from similar boletes by its cap color and non-reticulate stipe.

The cap is convex to cushion-shaped, before flattening out in maturity, attaining diameters of 4–18 cm. The cap margin is rolled or curved inward and remains that way until maturity.

Its surface is dry, with a velvet-like to slightly hairy texture. It often develops cracks in age. The cap color is variable, ranging from buff to olive-buff to olive-brown; it stains brown when bruised or injured.

The flesh is whitish to pale yellow, and will quickly turn blue when cut or exposed to air. The odor of the fruit body ranges from indistinct to unpleasant, and its taste is bitter. The pore surface on the underside of the cap is initially yellow before turning olive-yellow in age; it instantly turns blue when bruised.

The angular pores number about 1–3 per millimeter, and the tubes comprising the hymenophore are 8–16 mm long. The stem measures 5–12 cm long by 2–4.5 cm wide, and is either nearly equal in width throughout, or tapered slightly towards either end. The stem is solid , and has a dry surface with slight longitudinal grooves. Its color is pinkish-red to purple-red except for a yellow region near the top and yellow mycelium at the base. The stem lacks reticulation or an ring.

''Caloboletus rubripes'' produces an olive-brown spore print. Spores are somewhat spindle-shaped to somewhat cylindrical, smooth, and measure 12–18 by 4–5 μm. The basidia are club shaped, four-spored, and measure 26–30 by 7–13 μm. There are no clamp connections in the hyphae.

Naming

Somewhat similar in appearance is ''Caloboletus calopus'', which also has a red and yellow stipe, and a dry tan-colored cap. However, unlike ''C. rubripes'', it has a finely reticulate stipe. ''B. coniferarum'' is distinguished from ''C. rubripes'' by its stem reticulation and by the absence of red coloration.

Distribution

Found in North America, the distribution includes the Pacific Northwest region of the US , the southwestern US, and Mexico. They are particularly common in New Mexico and Colorado. Fruit bodies typically appear in the summer and fall. Alexander Smith has noted that they often appear with ''C. coniferarum'' and ''C. calopus''.

Habitat

The fruit bodies grow on the ground singly, scattered, or in clusters. They are usually found in coniferous forests, but also in association with oak.

Uses

The mushrooms are inedible owing to the bitter taste. They are used in mushroom dyeing to produce beige, light brown or light golden brown colors, depending on the mordant used.