Another Eurasian sp., is established in s.c. Wis. and may be expected elsewhere in our range. It differs in its perennial habit and its obtuse or rounded sep with a conspicuous white-scarious border 0.3-0.5 mm wide near the tip.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.