What You Should Know
Lactarius pubescens is a species of fungus in the family Russulaceae. It is a medium to large agaric with a creamy-buff, hairy cap, whitish gills, and short stout stem. This mushroom has a cosmopolitan distribution and grows solitarily or in scattered groups on sandy soil under or near birch. L. pubescens is fairly easy to identify a family of mushrooms with lactating gills and flesh.
Although it is unlikely to cause death or long-term illness, this poisonous species, which looks like a smaller, pallid and rather badly sheared version of the equally toxic Woolly Milkcap Lactarius torminosus, should not be gathered to eat. In Russia is consumed after prolonged boiling followed by a marinating process.
Other names: Downy Milkcap, The Bearded Milkcap.
Lactarius pubescens Mushroom Identification
3-7 cm broad, convex-depressed, plano-depressed in age; margin at first inrolled, then incurved, finally decurved; surface sticky when moist, more or less glabrous at the disc, elsewhere matted tomentose to fibrillose, the margin densely bearded; color: cream to cream-buff, tinged pale pinkish-orange, azonate to faintly zoned; context firm, white, unchanging, a narrow zone below the cuticle colored like the cap; odor mild, taste acrid.
The gills adnate to subdecurrent, crowded, cream, tinged pinkish-orange, often forked near the stipe, lamellulae up to four-seried; latex white, scanty, unchanging, or yellowing slowly.
2.5-4.0 cm long, 1.5-2.0 cm thick, dry, solid late into development, then hollow, brittle, equal, or the base narrowed to pinched; surface glabrous to inconspicuously pruinose (use hand lens), concolorous with the cap or lighter, typically not scrobiculate, sometimes darker where handled; partial veil absent.
Spores 6.5-7.5 x 4.5 x 5.0 µm, ellipsoid, with amyloid ornamentation consisting of raised warts and widely spaced ridges.
Pale ivory, sometimes with a faint salmon-pink tinge.
Scattered to gregarious under ornamental birches (Betula spp.); fruiting from late summer in watered areas, again after fall rains.
Lactarius pubescens Look-Alikes
Has a salmon pink woolly cap that is mover overtly zoned and has a very fibrous inrolled margin, and its spores are larger than those of Lactarius pubescens; it also grows under birch.
Lactarius scoticus Berk. & Broome
A small morphological mimic of L. pubescens, growing in arctic-alpine birch. L. pubescens is often mistaken for L. torminosus which has larger spores (7–10 by 6–8 µm).
Lactarius pubescens Taxonomy and Etymology
The Bearded Milkcap was described in 1815 by the great Swedish mycologist Elias Magnus Fries, who gave it the binomial scientific name Agaricus pubescens. It was also Fries who, in 1838, transferred this woodland mushroom species to its present genus, thereby establishing its name as Lactarius blennius, which is still its generally accepted scientific name today.
Synonyms of Lactarius pubescens include Agaricus pubescens Fr., Lactarius controversus var. pubescens (Fr.) Gillet, Lactifluus pubescens (Fr.) Kuntze, Lactarius torminosus var. pubescens (Fr.) S.Lundell.
The generic name Lactarius means producing milk (lactating) - a reference to the milky latex that is exuded from the gills of milkcap fungi when they are cut or torn. The specific epithet pubescens comes from Latin and refers to the fine downy hairs that fringe the caps of these mushrooms.
Photo 1 - Author: Bernard Spragg. NZ from Christchurch, New Zealand (Public Domain)
Photo 2 - Author: Holger Krisp (Creative Commons Attribution 3.0 Unported)
Photo 3 - Author: (Photo by E. Barge) Barge EG, Cripps CL (2016) New reports, phylogenetic analysis, and a key to Lactarius Pers. in the Greater Yellowstone Ecosystem informed by molecular data. MycoKeys 15: 1-58. https://doi.org/10.3897/mycokeys.15.9587 (Creative Commons Attribution 4.0 International)
Photo 4 - Author: Adrien BENOIT à la GUILLAUME (Creative Commons Attribution-Share Alike 4.0 International)