Cardaria chalepensis (Linnaeus) Handel-Mazzetti; C. draba (Linnaeus) Desvaux subsp. chalepensis (Linnaeus) O. E. Schulz; C. draba var. repens (Schrenk) O. E. Schulz; C. repens (Schrenk) Jarmolenko; Lepidium draba Linnaeus subsp. chalepense (Linnaeus) Thellung; L. draba var. repens (Schrenk) Thellung; L. repens (Schrenk) Boissier; Physolepidion repens Schrenk

Perennials; (rhizomatous); densely hirsute to glabrate or glabrous. Stems several from base, erect or decumbent basally, branched (several) distally, (0.8-)2.1-6.6(-9.2) dm. Basal leaves (early withered); not rosulate; petiole 0.9-4.4 cm; blade obovate, spatulate, or ovate, (1.8-) 2.5-8.6(-14) cm × 10-37 mm, margins subentire or dentate. Cauline leaves sessile; blade obovate to oblong or lanceolate to oblanceolate, (1.5-)2.6-9.3(-13.2) cm × (7-)12-31(-45) mm, base sagittate-amplexicaul or auriculate, margins dentate or entire, (surfaces pubescent or glabrous). Racemes (corymbose panicles), elongated in fruit; rachis glabrous or puberulent, trichomes cylindrical, straight or curved. Fruiting pedicels ascending to horizontal, straight, (terete), 5-16(-19) × 0.2-0.3 mm, glabrous or sparsely puberulent adaxially. Flowers: sepals oblong to ovate, 1.7-3 × 1-1.6 mm; petals white, obovate, 3-5 × 1.2-2.4 mm, claw 1.2-2 mm; stamens 6; filaments 2-3.3 mm, (glabrous); anthers 0.5-0.6 mm. Fruits (indehiscent), obovoid to subglobose or obcompressed globose, 3.5-5.8(-7) × (3.5-)4-6.2 (-7) mm, apically not winged, apical notch absent; valves thin, smooth, often not veined, glabrous; style (0.8-) 1.2-2(-2.3) mm. Seeds (dark reddish brown), ovate, 1.5-2.3 × 1-1.3 mm. 2n = 48, 80, 128.

Flowering May-Jun. Mountain slopes, roadsides, fields, agricultural lands, stream banks, pastures, waste areas; 300-4200 m; introduced; Alta., B.C., Man., Ont., Sask.; Ariz., Calif., Colo., Idaho, Ill., Iowa, Kans., Mont., Nebr., Nev., N.Mex., N.Dak., Oreg., S.Dak., Tex., Utah, Wash., Wyo.; Asia; introduced also in South America (Argentina), Europe.

From the synonymy above, it is evident that the disposition of Lepidium chalepense has varied: more than one species (e.g., R. C. Rollins 1940; G. A. Mulligan and C. Frankton 1962), one species (e.g., Rollins 1993), a variety of Lepidium (Cardaria) draba (N. H. Holmgren 2005b), or a synonym of the latter species (C. L. Hitchcock 1936). In our opinion, the differences in fruit morphology and chromosome number justify its recognition as a distinct species.