3. Erysimum asperum (Nuttall) de Candolle, Syst. Nat. 2: 505. 1821.
Cheiranthus asper Nuttall, Gen. N. Amer. Pl. 2: 69. 1818; Cheirinia aspera (Nuttall) Rydberg; Erysimum asperum var. dolichocarpum O. E. Schulz
Biennials. Trichomes of leaves 2- or 3-rayed. Stems erect, unbranched or branched distally, (0.6-)1.2-6.5(-8) dm. Basal leaves (often withered by fruiting); blade oblanceolate, 2-10 cm × (0.2-)0.5-1.5(-2.4) mm, base attenuate, margins dentate, apex acute. Cauline leaves (distal) sessile; blade margins entire or denticulate. Racemes considerably elongated in fruit. Fruiting pedicels horizontal to divaricate, slender, narrower than fruit, 5-16(-25) mm. Flowers: sepals oblong to linear-oblong, 8-12 mm, lateral pair slightly saccate basally; petals yellow, obovate to suborbicular, 13-22 × 4-9 mm, claw 8-15 mm, apex rounded; median filaments 8-14 mm; anthers linear, 2.5-4 mm. Fruits widely spreading or divaricate, narrowly linear, usually straight, rarely curved upward, not torulose, (3-)5-12(-14) cm × 1.2-2.7 mm, 4-angled, strongly (longitudinally) 4-striped; valves with prominent midvein and replum, densely pubescent outside, trichomes 2-rayed between midvein and replum, glabrous inside; ovules 72-120 per ovary; style cylindrical, slender, 1-4 mm, sparsely pubescent; stigma slightly 2-lobed, lobes as long as wide. Seeds ovoid, (1-)1.3-2.3 × 0.7-1.2 mm; usually not winged, rarely winged distally. 2n = 36.
Flowering Apr-Jun(-Aug). Prairies, sand dunes, roadsides, bluffs, sandhills along stream banks, knolls, open plains; 200-2000 m; Alta., Man., Sask.; Ark., Colo., Ill., Kans., Minn., Mont., Nebr., N.Mex., N.Dak., Okla., S.Dak., Tex., Wyo.