Rumex obtusifolius L.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Stout perennial to 12 dm from a large tap or branched root, usually single-stemmed and simple to the infl; lower lvs cordate at base, broadly oblong to ovate, to 15 cm wide, the upper much smaller; infl freely branched, the lower verticils commonly separate and leafy-bracted; pedicels conspicuously longer than the fr, jointed below the middle; valves triangular-ovate, 3.5–5 mm, with 2–4 spinose teeth on each margin, one bearing a large, minutely wrinkled grain, the others merely with a slightly thickened midrib; 2n=50. Native of Europe, commonly naturalized in waste ground, especially in moist soil, from Que. and N.S. to B.C., s. to Fla. and Ariz.