Biennials. Trichomes of leaves mostly 3- or 4-rayed, 2-rayed ones usually on stem and pedicel. Stems erect, often branched distally, (slightly ribbed), (1-) 3-9(-11) dm. Basal leaves (withered by fruiting; petiole 1-4 cm); blade elliptic-oblong or oblanceolate, (1-)2-6(-8) cm × (0.3-)5-10 mm, base cuneate, margins entire or obscurely denticulate, apex acute. Cauline leaves sessile or subsessile; blade (linear or elliptic-linear), margins entire or obscurely denticulate. Racemes considerably elongated in fruit. Fruiting pedicels suberect or ascending, slender, narrower than fruit, (3-)4-8(-10) mm. Flowers: sepals oblong, 4-7 mm, lateral pair not saccate basally; petals yellow, obovate, (6-)7-9(-10) × 2-3 mm, claw 5-8 mm, apex rounded; median filaments 4-6 mm; anthers oblong, 1.5-2 mm. Fruits erect, (often appressed to rachis), linear, straight, somewhat torulose, (1-)1.5-2.5(-4) cm × 1-1.3 mm, 4-angled, not striped; valves with prominent midvein, pubescent outside, trichomes 3- or 4-rayed, fewer 2-rayed ones, usually glabrous inside, rarely sparsely pubescent; ovules 40-60 per ovary; style cylindrical, slender, 0.5-2 mm; stigma capitate, entire. Seeds oblong, 1-1.5 × 0.4-0.6 mm; not winged.

Flowering Jun-Sep. Moist areas, disturbed sites, grasslands, roadsides, waste ground; 50-300 m; introduced; Man., N.B., N.S., Ont., Que., Sask.; Mass., Vt., Wis.; Eurasia.

Biennial or perennial, much like no. 5 [Erysimum inconspicuum (S. Watson) MacMill.], usually but not always with somewhat broader lvs, these to 1 or even 1.5 cm wide and sometimes evidently toothed; hairs of the upper lf-surface mainly 3-pronged, with a considerable admixture of 4-pronged ones; 2n=32, 40. European weed, now found from N.S. to Sask., Mich., and Wis. June, July.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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