[9] L. tomentosomarginatus, described by Hesler and Smith in their 1979 monograph of North American milk-caps, was considered by them to be a "satellite species", differing from L. deceptivus on the basis of smaller spores, smaller ornamentations on the surface of the spores, crowded and forked narrow gills, and differences in the micro-structure of the cap cuticle.

The cap surface is dry, smooth and whitish when young, often with yellowish or brownish stains, but becomes coarsely scaly and darkens to dull brownish-ochre with age.

[12] The odor of the flesh and latex may range from indistinct to pungent or turnip-like in age; the taste is strongly acrid—so much that it may have an anesthetizing effect in the throat.

The pleurocystidia (cystidia found on the face of a gill) are very abundant, roughly club-shaped to ventricose (swollen in the middle), with apices often tapering; their dimensions are 48–96 x 6–10 μm.

[13] The fungus Lactifluus pseudodeceptivus is very similar to L. deceptivus in its external appearance, but it has spore ornamentation that forms a reticulum, and its stem is an ixocutis (a gelatinous layer of hyphae lying parallel to the surface).

Lactifluus piperatus has densely crowded gills, a firm rather than soft and cottony cap margin, and exceedingly acrid latex.

[4] Like all milk-caps (Lactarius and Lactifluus), L. deceptivus is mycorrhizal, meaning the fungus forms a mutualistic association with certain trees and shrubs.

The subterranean mycelium of the fungus forms an intimate association with tree roots, enveloping them in a sheath of tissue that allows both organisms to exchange nutrients they would otherwise be unable to obtain.

The fruit bodies of the fungus grow solitarily, scattered, or in groups on the ground in conifer or hardwood forests, often under oak (Quercus) or hemlock (Tsuga).

Smith has noted a preference for bogs and the edges of woodland pools in hardwood forests, and in oak stands that have an understory of blueberry bushes (Vaccinium species).

[17] It is widely distributed in eastern North America (appearing from July to September),[11] and has also been reported from southern[12] and western Canada.

"[2] Thorough cooking removes the bitter taste,[13] but the mushroom is not highly regarded as an edible,[4] and as Hesler and Smith have noted, "some of our acquaintances have found it rather undesirable (and indigestible).