Beih. Bot. Centralbl. 37(2): 113. 1919.
Plants annual, 10–20(–70) dm; roots not also arising from proximal nodes. Stems scandent, ribbed, glabrous, often glaucous; prickles 0.5–1 mm. Leaves: ocrea green, plane to broadly funnelform, 9–14 mm, at least some foliaceous, base inflated or not, without prickles, margins oblique, eciliate, surface glabrous, glaucous; petiole 4.5–8 cm; blade triangular, 4–7 × 4.5–9 cm, base truncate to cordate, usually peltate, margins entire, sparsely retrorsely prickly, apex acuminate, faces glabrous, usually glaucous abaxially. Inflorescences capitate or spikelike, uninterrupted, 5–12 × 5–10 mm; peduncle 10–50 mm, retrorsely prickly; ocreolae overlapping, margins eciliate. Pedicels mostly ascending, 1–3 mm. Flowers 1–3 per ocreate fascicle; perianth greenish white, glabrous, accrescent, becoming fleshy and blue in fruit; tepals 5, connate to ca. 1/3 their length, broadly elliptic, 2–3.5 mm, apex acute to obtuse; stamens (6–)8, filaments distinct, free; anthers pinkish, ovate; styles 3, connate proximally. Achenes included, black or reddish black, spheroidal, 3–3.5 × 3–3.5 mm, shiny, smooth.
Phenology: Flowering Jun–Oct.
Habitat: Thickets, streams banks, pastures, forest edges, roadsides, railroad embankments, other moist, disturbed sites
Elevation: 0-300 m
Introduced; Conn., Del., D.C., Md., Miss., N.J., N.Y., Ohio, Oreg., Pa., R.I., Va., W.Va., Asia.
Persicaria perfoliata is an aggressive, fast-growing pest in its native range and in North America. At least some introductions appear to be through the nursery trade (J. C. Hickman and C. S. Hickman 1978; R. E. Riefener 1982). It was collected once in 1954 in British Columbia, but that population did not persist.