Conservation Status: Not of concern
Hydnellum caeruleum differs from H. aurantiacum in its coloration, but otherwise is very similar. When young, the cap includes shades of blue, blue-gray, and brown, with the paler blue tones occurring near the edge. The spines are brownish, with blue overtones prominent when young, and the stipe is orange-brown to brown. The flesh of the cap is bluish to grayish to nearly black, and that of the stipe is red- to orange-brown. Most of the blue colors disappear in age, and older fruitbodies look much the same as those of H. aurantiacum. Another species with blue colors is H. suaveolens. Its cap usually is yellowish brown with a whitish or very pale blue edge, the flesh is entirely blue, and the mushroom has a strong sweet anise odor. H. caeruleum is a widespread fungus, occurring throughout much of North America, Europe, and temperate Asia.