Lactarius uvidus

[ Basidiomycetes > Russulales > Russulaceae > Lactarius . . . ]

by Michael Kuo

Lactarius uvidus is a "species" frequently represented in field guides--but descriptions and photos vary fairly widely. It seems probable that, as Lactarius experts Hesler and Smith suggested over two decades ago, "Lactarius uvidus" is actually a constellation of related, similar mushrooms. Whether or not any of our North American versions truly match the original European species is anyone's guess. However, mushrooms in the North American Lactarius uvidus cluster are characterized by the following features:

• White milk that stains the gills and flesh purplish.
• A green reaction to KOH on the cap surface.
• Mild or somewhat bitter (but not strongly acrid) taste.
• A drab lilac cap that becomes darker with age.

Several variants have been described; see the comments below for details.

The European Lactarius uvidus is thought to be poisonous. I do not recommend experimenting with North American mushrooms in this group.

Description:

Ecology: Mycorrhizal with Quaking Aspen, birch, and pines; growing alone or gregariously; summer and fall; widely distributed in North America.

Cap: 3-10 cm; broadly convex with an inrolled margin when young; becoming shallowly depressed or vase-shaped, with an uplifted margin; slimy or sticky when fresh, but often dry; fairly smooth; pale drab lilac, darkening with age and often lilac brown or merely brownish when mature; without zones of color, or with faint zonations.

Gills: Beginning to run down the stem; close; white when young, pale tan in age; staining and bruising purplish.

Stem: 3-7 cm long; 1-1.5 cm thick; equal; smooth (very rarely with potholes); slimy or sticky when very fresh and young, but soon dry; whitish, often bruising or discoloring brownish near the base.

Flesh: White; firm; becoming purplish when sliced, due to the milk.

Milk: White, becoming creamy on exposure to air; staining all surfaces purplish.

Odor and Taste: Odor not distinctive; taste mild or somewhat bitter (never strongly acrid).

Spore Print: Pale yellowish.

Chemical Reactions: Cap surface green with KOH.

Microscopic Features: Spores 9-11 x 7-8.5 µ; broadly elliptical or nearly round; ornamentation consisting of broad ridges extending 0.5-1 µ high; not forming a reticulum.

REFERENCES: (Fries, 1818) Fries, 1838. (Fries, 1821; Saccardo, 1887; Kauffman, 1918; Hesler & Smith, 1979; Smith, Smith & Weber, 1979; Arora, 1986; States, 1990; Phillips, 1991/2005; Lincoff, 1992; Evenson, 1997; Methven, 1997; Heilmann-Clausen et al., 1998; McNeil, 2006; MIller & Miller, 2006.) Herb. Kuo 09130408, 08160708.

Hesler & Smith describe Lactarius uvidus var. montanus, under conifers in Idaho. Its cap is purplish brown, its milk stains the tissues vinaceous to vinaceous brown, and its taste is "resinous." Evenson (1997) describes and illustrates this variant from high-elevation conifer bogs in Colorado. Another variant, Lactarius uvidus var. acystidiosus, is described by Hesler and Smith on the basis of a Nova Scotian collection under conifers. It lacks cystidia and has longer (9-10.5 x 6.5-7.5 µ) spores.

Further Online Information:

Lactarius uvidus in Hesler & Smith (1979)
Lactarius uvidus at Roger's Mushrooms
Lactarius uvidus at Russulales News
Lactarius uvidus at Fungi of Poland

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Cite this page as:

Kuo, M. (2004, September). Lactarius uvidus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/lactarius_uvidus.html