Biennial or perennial herb 30 cm - 0.8 m tall Stem: upright, usually unbranched, grayish green, very hairy. Leaves: alternate, usually upright or ascending, grayish green, to 1.5 cm wide, linear to oblong, sometimes toothed. The upper leaf surface is covered with mostly three-pronged hairs and a few four-pronged ones. Flowers: in a long, branched cluster (raceme). Stalks ascending, 3 - 9 mm long, stout. Sepals four, 4.5 - 7 mm long, densely hairy. Petals four, pale yellow, 6 - 10 mm long. Stamens six. Fruit: a long, narrow pod, upright or nearly so, 1.5 - 4 cm long, four-angled, and hairy. Seeds in one row.
Similar species: The similar Erysimum cheiranthoides differs by having petals that do not typically exceed 5 mm long, sepals that do not typically exceed 3.5 mm long, and fruit that does not typically exceed 3 cm long. Erysimum inconspicuum differs by having leaves that lack four-pronged hairs on the upper surface and that are more or less non-toothed along the margins. Erysimum repandum, which is a pale green annual, typically has fruit more than 5 cm long.
Flowering: late May to early July
Habitat and ecology: Introduced from Europe. Occasional along roadsides and railroads.
Occurence in the Chicago region: non-native
Etymology: Erysimum comes from the Greek word eryomai, meaning "to help or save," which refers to the medicinal qualities of some species.