[ Basidiomycota > Cantharellales > Hydnaceae > Hydnum ... ]

Hydnum species 01

by Michael Kuo, 18 June 2025

This hedgehog mushroom is an undescribed phylogenetic species from the conifer forests of the Rocky Mountains, featuring medium sized caps (on the Hydnum scale), orange to dull orange colors, a whitish stem that discolors slightly orange, and, under the microscope, variable spores that range from ellipsoid to tear-shaped or nearly round. It has doubtless been identified as "Hydnum repandum" and "Hydnum umbilicatum," but the former is a strictly European species and the latter is a northeastern North American species best identified with DNA sequencing.

There may be several western North American, montane, conifer-associated species of Hydnum; phylogenetic sampling from the region has been minimal so far. Descriptions and photos in western North American mountain field guides (e.g. Schalkwijk-Barendsen 1991, Evenson 2015, Cripps, Evenson & Kuo 2016) are plausible matches for "species 01," but studies have shown Hydnum to be full of cryptic species that are not easily separated on the basis of physical features.

Thanks to Rachel Swenie for studying the collection described and illustrated here; preliminary results appear in Baroni et al. 2025 (where the species is given the temporary name "sp. 6"), and several sequences can be found at GenBank by searching "MK08141509."

Description:

Ecology: Mycorrhizal with Engelmann spruce and/or subalpine fir, and possibly with pines; growing gregariously on the ground; summer; distributed in the Rocky Mountains, with precise distribution as yet unknown (documented from Colorado and Idaho). The illustrated and described collection is from Dolores County, Colorado.

Cap: 3–6 cm wide; broadly convex, becoming planoconvex; dry; soft; becoming finely pocked and roughened; brownish orange to pale orange; the margin sometimes inrolled and whitish.

Undersurface: Not running down the stem, or just beginning to do so; covered with densely packed, soft spines that are round in cross-section and measure 2–5 mm long; creamy; not bruising.

Stem: 3–6 cm long; 1–1.5 cm thick; dry; bald; whitish; discoloring and staining pale yellow-orangish.

Flesh: Whitish; unchanging when sliced.

Odor: Not distinctive.

Chemical Reactions: KOH negative on cap surface and on spines. Iron salts negative on cap surface and on spines.

Microscopic Features: Spores 7–10 x 4–7 µm; ellipsoid, lacrymoid, or nearly subglobose; apiculate; smooth; hyaline and multiguttulate in KOH; inamyloid. Basidia 4-sterigmate; 25–30 x 6–8 µm; subclavate. Pseudocystidia 30–60 x 3–4 µm; cylindric with rounded apices; thin-walled; smooth; hyaline to yellowish in KOH. Pileipellis not clearly differentiated; cap surface hyphae tangled, 3–6 µm wide, hyaline in KOH, with clamp connections; terminal cells cylindric with rounded apices.

REFERENCES: (Schalkwijk-Barendsen, 1991; Evenson, 2015; Cripps, Evenson & Kuo, 2016; Baroni et al., 2025.) Herb. Kuo 08141509.

This site contains no information about the edibility or toxicity of mushrooms.

Spores

© MushroomExpert.Com

Cite this page as:

Kuo, M. (2025, June). Hydnum species 01. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/hydnum_species_01.html