Much like O. biennis var. biennis, but with broader cauline lvs and larger fls, the sep 2-6 cm, with tips 5-8 mm, the pet 3-5 cm, the styles 2-6 cm; 2n=14, a complex heterozygote. Cultigen, widely but sparingly escaped. (O. erythrosepala; O. lamarckiana, misapplied)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.