Great Water Dock

Appearance

Plants perennial, normally gla-brous or very indistinctly papillose on veins of leaf blades abaxially, with fusiform, vertical rootstock. Stems erect, branched distal to middle, 80-150(-200) cm. Leaves: ocrea deciduous or partially persistent at maturity; blade lanceolate or oblong-lanceolate, normally 20-55(-70) × 2-7 cm, base cuneate, occasionally rounded or truncate, margins entire, flat to slightly crisped, apex acute. Inflorescences terminal, occupying distal 2 of stem, dense or interrupted in proximal 1/ 2, broadly paniculate, branches usually straight or arcuate. Pedicels articulated in proximal 3, filiform, 5-13 mm, articulation barely evident, not distinctly swollen. Flowers 15-25 in whorls; inner tepals orbiculate or orbiculate-ovate, rarely ovate-deltoid, 4-7(-7.5) × 3.5-7 mm, base truncate or slightly cordate, margins entire or weakly erose, flat, apex obtuse to subacute; tubercles 3, equal or subequal, normally less than 2 times as wide as inner tepals. Achenes usually reddish brown, 3-4.5 × 1.5-2.5 mm. 2n = 20.

Naming

Rumex britannica L.
Rumex orbiculatus A. Gray
Rumex britannica var. borealis Rechinger
Rumex hydrolapathum Hudson var. americanum A. Gray

Distribution

Alta., Man., N.B., Nfld. and Labr. (Nfld.), N.W.T., N.S., Ont., P.E.I., Que., Sask.; Calif., Conn., D.C., Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Nebr., N.H., N.J., N.Y., N.Dak., Pa., R.I., S.Dak., Vt., Va., Wis.

Habitat

Moist to very wet ground or shallow water of peatlands, river margins, marshes, ponds, swales, and ditches.