Annual, 3-6 dm, glabrous and glaucous; lower lvs oblong to obovate, sessile or somewhat petiolate; upper lvs perfoliate, ovate, 2-5 cm; umbels peduncled, the 4-10 rays spreading or ascending, 0.5-2 cm; bracts none; bractlets broadly ovate to elliptic, acuminate, 8-12 mm, much surpassing the subsessile fls; fr dark brown or black, oblong-elliptic, 2.5-3 mm, obscurely ribbed; 2n=16. Native of Europe and w. Asia, established as a weed in fields and waste places from s. N.Y. to s. Ind. and Kans., s. to N.C. and Ark., and occasionally adventive elsewhere. May, June.
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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