10. Lepidium virginicum L. (poor man’s pepper grass, pepper grass, Virginia pepper grass)

Pl. 323 j–l; Map 1369

Plants annual or biennial. Stems (6–)15–55(–70) cm long, erect or ascending, pubescent especially in the upper parts with minute, curved, mostly ascending hairs with pointed tips (visible with magnification). Leaves (1.0–)2.5–10.0(–15.0) cm long, linear to oblanceolate or elliptic to obovate in outline, the bases not clasping, glabrous or less commonly minutely hairy on the undersurface, the lower and basal leaves often 1 time pinnately lobed, rarely 2 times lobed, the margins entire to coarsely toothed, petiolate, the upper leaves reduced, linear, sessile or nearly so, the margins usually entire. Sepals (0.5–)0.7–1.0(–1.1) mm long, linear to narrowly elliptic. Petals 1.5–2.5 mm long, white, rarely rudimentary. Stamens 2. Styles 0.1–0.2 mm long. Fruits 2–4 mm long, circular, widest at the middle, the tip shallowly notched and sometimes narrowly winged, flattened, glabrous. Seeds 1.1–1.7(–1.9) mm long, narrowly obovate to elliptic in outline, usually winged around most of the margin or at least at the tip, the surface minutely roughened, light orange. 2n=32. April–November.

Common nearly throughout Missouri (Canada, U.S., widely introduced in South America, Europe, Asia). Glades, tops of bluffs, prairies, and rocky openings of dry upland forests; also pastures, crop fields, fallow fields, old fields, railroads, roadsides, and open, disturbed areas.

For a discussion of the separation of this species from the closely related L. densiflorum, see the treatment of that species. As in L. densiflorum, several varieties have been named that appear to be based mostly upon trivial characters of pubescence density and distribution, as well as slight differences in the shape and size of the fruits and their stalks. Missouri plants have always been attributed to var. virginicum, but the varieties seem unworthy of taxonomic recognition.