Acta Univ. Upsal., Symb. Bot. Upsal. 22: 72. 1978.
Plants annual, 2–15 dm; roots also often arising from proximal nodes. Stems scandent, ribbed, glabrous; prickles 0.5–1 mm. Leaves: ocrea tan or brownish, cylindric, 8–15 mm, chartaceous, base inflated or not, with prickles, margins oblique, ciliate with bristles 0.5–2.5 mm, surface glabrous or appressed- to spreading-pubescent; petiole 1–7 cm; blade broadly hastate to hastate-cordate or triangular, (2–)6.5–13(–18) × (1–)6–11(–16) cm, base truncate to truncate-cordate, margins broadly hastate with lobes divergent, ciliate, sometimes also retrorsely prickly, apex acuminate, faces appressed-pubescent or, rarely, glabrous adaxially, stellate-pubescent or, rarely, glabrous abaxially, major veins often bearing prickles. Inflorescences capitate or paniclelike, uninterrupted, 5–12 × 3–8 mm; peduncle 10–80 mm, retrorsely prickly proximally, stellate-pubescent and stipitate-glandular distally, glands red or pink; ocreolae usually overlapping, sometimes not overlapping proximally, margins eciliate or ciliate with bristles to 0.5 mm. Pedicels mostly ascending, 2–3 mm. Flowers 2–4 per ocreate fascicle; perianth pink or red, often whitish green proximally, glabrous, accrescent, not becoming blue and fleshy in fruit; tepals 4, connate 1/3–1/2 their length, broadly elliptic, 5–6 mm, apex acute to obtuse; stamens (6–)8, filaments distinct, free; anthers pink, elliptic; styles 2, distinct. Achenes included, dark brown to black, biconvex, 3.5–6 × 3–4 mm, shiny, smooth.
Phenology: Flowering Jul–Oct.
Habitat: Shaded swamps, ponds, tidal marshes along rivers, wet ravines in forests
Elevation: 0-600 m
N.B., N.S., Ont., P.E.I., Que., Conn., Del., D.C., Ga., Ill., Ind., Ky., La., Maine, Md., Mass., Mich., Minn., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Vt., Va., Wash., W.Va., Wis.