Slender annual 1-4 dm, the stem often retrorse-scabrous on the angles; lvs in whorls of 5-8, often 6, linear or linear-oblanceolate, mucronate, 1-nerved, 4-10 mm, antrorsely scabrous on the margins; fls in small cymes ending the mostly numerous branches; cor minute; fr 1 mm, the segments approximate; 2n=22, 44, 55, 66. Native of Europe, intr. as a weed in fields and roadsides in the s. part of our range. June-Aug. Our plants, with the slightly granular-roughened, otherwise glabrous frs, are var. leiocarpum Tausch. (G. divaricatum) Var. parisiense has hooked hairs on the frs.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.