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Lactarius repraesentaneus

[ Basidiomycota > Russulales > Russulaceae > Lactarius . . . ]

by Michael Kuo

I can't imagine mistaking this mushroom for anything else. Found under spruces in northern and montane areas, it has a slimy, hairy, yellow cap that contrasts nicely with the purple bruises and stains created by handling the mushroom or damaging the gills. When fresh it has a distinctive, fragrant odor. The true Lactarius repraesentaneus is a European, spruce-associated species; whether or not our North American version is phylogenetically the same has not been determined, to my knowledge.

The spores of the Colorado collections I have studied are substantially smaller than what is usually reported for the species by European sources—and by Hesler & Smith (1979), despite the fact that one of the collections I studied is cited by them. My friend Vera Evenson (author of Mushrooms of the Rocky Mountain Region, 2015) has also noted smaller-than-reported spore sizes for Colorado material. What about your collections? Let me know at if you have a well-documented, preserved Lactarius repraesentaneus collection for comparison!

Thanks to Mila Visser 't Hooft for documenting, collecting, and preserving Lactarius repraesentaneus for study; her collection is deposited in The Herbarium of Michael Kuo. Thanks to the Sam Mitchel Herbarium of Fungi at the Denver Botanic Gardens for facilitating my study of several collections, and for permission to share with my readers Shirley Chapman's photo of the material in the fresh state; thanks also to Danila Romanov for sharing his photos of one of the collections.


Ecology: Mycorrhizal with spruces (in the southern Rocky Mountains it is fond of Engelmann spruce); summer and fall; widely distributed in northern and montane North America. The illustrated and described collections are from California and Colorado.

Cap: 4–14 cm; convex with an incurved margin when young; becoming flat, shallowly depressed, or shallowly vase-shaped; slimy when fresh; hairy—especially at the margin, which is "bearded" when the mushroom is young; pale to dark yellow or orangish yellow; usually without concentric zones of color; often bruising lilac to purple when handled.

Gills: Attached to the stem or beginning to run down it; close; short-gills frequent; sometimes forked near the stem; whitish at first, becoming yellowish or orangish; stained lilac to purple by the milk where damaged.

Stem: 3–8 cm long; up to 3 cm thick; more or less equal, or slightly club-shaped; slimy when fresh; usually featuring potholes; whitish or pale yellowish; bruising and discoloring lilac to purple; becoming hollow; basal mycelium white.

Flesh: White; changing to lilac when sliced.

Milk: White; copious; staining tissues lilac to purple.

Odor and Taste: Odor fragrant or not distinctive; taste usually bitter to acrid, but sometimes mild.

Chemical Reactions: KOH red on cap surface.

Spore Print: Creamy or yellowish.

Microscopic Features: Spores 6.5–8 x 5.5–7 µm in the collection I have studied, but usually reported as somewhat larger (9–11 µm long); broadly ellipsoid to nearly subglobose; ornamentation as amyloid spines and connecting lines up to 0.5 µm high, often forming striped patterns and partial reticula (and sometimes nearly completely, though widely, reticulate). Hymenial cystidia fusiform, with long tapering necks that feature several apical constrictions; to about 90 x 10 µm. Pileipellis an ixocutis of elements 2.5–5 µm wide, golden in KOH.

REFERENCES: Britzelmayr, 1885. (Saccardo, 1887; Hesler & Smith, 1979; Smith, Smith & Weber, 1979; Arora, 1986; States, 1990; Lincoff, 1992; Heilmann-Clausen et al., 1998; Kränzlin, 2005; McNeil, 2006; Miller & Miller, 2006; Evenson, 2015.) Herb. DBG 2696, CMS-2018-0388. Herb. Kuo 09221901.

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


Lactarius repraesentaneus

Lactarius repraesentaneus

Lactarius repraesentaneus

Lactarius repraesentaneus

Lactarius repraesentaneus

Lactarius repraesentaneus

Lactarius repraesentaneus

Lactarius repraesentaneus

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Kuo, M. (2019, November). Lactarius repraesentaneus. Retrieved from the MushroomExpert.Com Web site: