The mushrooms produced by the fungus have convex to flattened drab lilac-colored caps that are up to 18 cm (7.1 in) wide.

Variety dissimilis, described on the basis of a single specimen from South Carolina, differs from the main form in the microscopic structure of the cap cuticle.

[2] Hesler and Smith simultaneously published the varieties dissimilis and megacarpus, collected from South Carolina and California, respectively.

The cap surface is covered with fine soft hairs when young, but later becomes smooth; it is slimy and sticky when wet.

The latex is creamy-white on initial exposure, and stains the gills grayish-brown to dark brown or olive-brown; its taste is mild or slowly becomes slightly acrid.

The cap cuticle of young specimens is made of a tissue type known an ixotrichoderm, which contains gelatinized hyphae of different lengths arranged in roughly parallel fashion.

dissimilis, a variety reported from South Carolina, is nearly identical in appearance, but it has white latex that tastes bitter then acrid.

The structure of the cap cuticle differs from the nominate variety in that it has dextrinoid (staining yellowish or reddish brown with Meltzer's reagent) incrustations on the hyphae.

It's latex is off-white, and stains fungal tissue brown to brownish, and its spore print is whitish to buff.

[11] L. trivialis can be distinguished by gills that stain brown when exposed to the latex, and a preference for growing in conifer- and birch-rich boreal and subalpine forests.

[12] Variety megacarpus may be confused with L. pallescens, a smaller paler-colored species with latex that stains gills lilac rather than brown.

[13] Additionally, L. hibbardiae has a zonate cap, L. kauffmanii has a tan to gray pileus, and L. uvidus stains purple.

The fruit bodies of Lactarius argillaceifolius grow scattered or in groups on the ground under hardwoods, especially oak, from July to October.