What You Should Know
Lactarius argillaceifolius is one of several North American species that are similar to the European species Lactarius Trivialis. But while Lactarius Trivialis favors conifers and birches in boreal and subalpine forests in Europe, Lactarius argillaceifolius associates with oaks in eastern North America.
Also unlike L. Trivialis, L. Argillaceifolius has gills that are stained brownish by the milk. Other defining features include the dingy cinnamon color of the mature gills, the drab lilac cap color, and the off-white (rather than pure white) color of the milk.
Other names: Clay-gilled Milkcap, Common Milk Cap, Vulgar Milkcap.
Lactarius argillaceifolius Mushroom Identification
Mycorrhizal with oaks; growing alone or gregariously; spring (it is often one of the first mycorrhizal mushrooms to appear in oak-hickory forests), summer and fall; widely distributed east of the Rocky Mountains.
3-18 cm; convex becoming flat or shallowly vase-shaped; drab cinnamon to drab lilac brown; without zones; bald or minutely pocked and rugged; sticky when fresh.
Beginning to run down the stem; close or crowded; cream-colored when young, becoming dingy cinnamon with age; stained slowly brown (or rarely olive to greenish) by the latex where damaged.
3-9 cm long; 1-3.5 cm thick; tapering to base; pale or brownish in age; dry or slightly sticky; smooth; without potholes.
White; unchanging, or discoloring faintly tan.
Off-white; unchanging when exposed; staining tissues brown to brownish, or rarely olive to greenish; over time staining white paper yellow.
Odor and Taste
Odor not distinctive to mildly fragrant; taste mild to slowly slightly acrid.
KOH on cap surface erasing pigments to pale orange or tan.
Spores 8-10 x 7-8 µ; broadly ellipsoid or subglobose; ornamentation 0.5-1 µ high, composed of fairly isolated warts and ridges that sometimes form broken reticula. Pleuromacrocystidia fusoid-ventricose; to 100+ µ long. Cheilomacrocystidia similar but usually shorter. Pileipellis an ixolattice.
Lactarius argillaceifolius Taxonomy
The species was first described by American mycologists Lexemuel Ray Hesler and Alexander H. Smith in their 1979 monograph on the North American species of Lactarius. The type specimen—collected by Smith from Oak Grove, Livingston County, Michigan, in July 1972—is housed at the University of Michigan Herbarium. Hesler and Smith simultaneously published the varieties dissimilis and megacarpus, collected from South Carolina and California, respectively. The variety megacarpus is commonly known as the "vulgar milkcap".
Smith and Hesler classified L. argillaceifolius in subgenus Tristes, in stirps Argillaceifolius. This grouping of related species, which includes L. fumaecolor, is characterized by the gelatinous cuticle of the stem.
Photo 1 - Author: Boleslaw Kuznik (Bolek) (Creative Commons Attribution-Share Alike 3.0 Unported)
Photo 2 - Author: Dan Molter (shroomydan) (Creative Commons Attribution-Share Alike 3.0 Unported)
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Photo 4 - Author: Richard Sullivan (enchplant) (Creative Commons Attribution-Share Alike 3.0 Unported)