What You Should Know
Hydnellum aurantiacum can be recognized by the velvety, irregularly shaped rusty orange to cinnamon cap with a bumpy surface, short white to orangish brown spines, a mild odor, and orange to rusty cinnamon context tissues. Like other tooth fungi, it bears a layer of spines rather than gills on the underside of the cap. It is mycorrhizal with conifers, primarily with pines and eastern hemlock in eastern North America, and firs and Douglas-fir in western North America. However, the species has also been observed growing under hardwoods.
It is widely distributed in North America and some parts of Europe, but there has been a decline in sightings of this species in the United Kingdom.
H. aurantiacum is used in mushroom dyeing, which produces grayish to greenish-gray colors depending on the mordant used.
Other names: Orange Spine, Orange Hydnellum, Orange Corky Spine Fungus.
Hydnellum aurantiacum Mushroom Identification
Mycorrhizal with conifers (especially pines and eastern hemlock, and fir or Douglas-fir in the Pacific Northwest) and perhaps occasionally with hardwoods; growing alone or gregariously; summer and fall (or overwinter in warm climates); widely distributed in North America.
Usually single but occasionally fused with other caps; 3-10 cm wide; flat, becoming shallowly depressed; sometimes with aborted mini-caps developing on top of the main cap; pocked, pitted, ridged, or elaborately sculpted; orange to rusty red overall, with a whitish to a dingy pinkish margin that often bruises brownish to blackish.
Running down the stem or not; covered with crowded spines that are 2-5 mm long; whitish at first, becoming dingy.
2-5 cm long; 1-2 cm thick at apex; cylindric, club-shaped, or somewhat irregular; sometimes spongy near the base; orange to rusty red.
Two-layered, with a softer upper layer in the cap that is whitish to dull orangish--and in the stem and lower cap a corky, an orangish-brownish lower layer that sometimes features zones of contrasting shades.
Odor and Taste
Odor fragrant; taste somewhat unpleasant.
KOH on flesh greenish to brown or black.
Spores 4.5-9 x 4-7 µ; subglobose or irregular; prominently tuberculate. Clamp connections absent.
The species resembles the polypore Phaeolus schweinitzii when viewed from the top of the cap surface, but it has teeth instead of pores on the hymenium. Closely related and morphologically similar species in the genus Hydnellum include H. auratile (has more uniformly coloured flesh), H. caeruleum (may look similar in age), H. congenum (has thin flesh in the cap), H. ferrugipes, H. earlianum (has a smoother cap, and spines have sulfur-yellow tips, not white).
Hydnellum aurantiacum Taxonomy and Etymology
Hydnellum aurantiacum was first described by the German naturalist August Batsch in 1789, with the name Hydnum suberosum var. aurantiacum. It was given its current scientific name by Petter Karsten, who transferred it to Hydnellum in 1879.
Synonyms: Hydnum stohlii, published by Gottlob Ludwig Rabenhorst in 1873, and Hydnellum complectipes, published by Hall in 1972. Additional synonyms resulting from generic transfers include Hydnum aurantiacum (Johannes Baptista von Albertini and Lewis David de Schweinitz, 1825); Calodon aurantiacus (Karsten, 1881); and Phaeodon aurantiacus (Joseph Schröter, 1888).
The specific epithet aurantiacum is derived from the Latin for "orange".
Hydnellum aurantiacum Chemistry
The pigment responsible for the characteristic orange color of H. aurantiacum has been identified as the p-terphenyl compound named aurantiacin. This dark red pigment, a derivative of the compound atromentin, has subsequently been identified in other species of Hydnellum. The compounds dihydroaurantiacin dibenzoate and thelephoric acid have also been reported.
Photo 1 - Author: Jimmie Veitch (jimmiev) (Creative Commons Attribution-Share Alike 3.0 Unported)
Photo 2 - Author: caspar s (Creative Commons Attribution 2.0 Generic)
Photo 3 - Author: Leah Bendlin (Leah Bendlin) (Creative Commons Attribution-Share Alike 3.0 Unported)
Photo 4 - Author: Photo by Karen Dillman, Tongass Ecologist, Mitkof Island (Public Domain)
Shape: Funnel-shapedTooth Fungi
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