2. Persicaria perfoliata (Linnaeus) H. Gross, Beih. Bot. Centralbl. 37(2): 113. 1919.
Devil's-tail or giant climbing tearthumb, mile-a-minute weed
Polygonum arifolium Linnaeus var. perfoliatum Linnaeus, Syst. Nat. ed. 10, 2: 1006. 1759; P. perfoliatum (Linnaeus) Linnaeus
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.
Flowering Jun-Oct. Thickets, streams banks, pastures, forest edges, roadsides, railroad embankments, other moist, disturbed sites; 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.