Prostrate to ascending annual, much like no. 8 [Polygonum arenastrum Boreau], but more sparsely branched, and with narrower, linear oblong to lance-linear lvs 8-30 mm; perianth avg a bit larger, to 3 mm, divided half to 3/4 length; achenes avg larger, 2-3 mm; 2n=40, 60. A weed of roadsides, vacant lots, and pastures, seldom on beaches and dunes; Eurasia and much of N. Amer., doubtfully native. (P. franktonii, of maritime and freshwater beaches, dunes, and shores in se. Can.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.