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.