This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Polygonum Hydropiper L. Sp. PI. 361. 1753. Persicaria Hydropiper Opiz, Seznam 72. 1852.
Annual, glabrous, stem erect, simple or branched, red or reddish, sometimes green, 8'-24' tall. Leaves lanceolate or oblong-lanceolate, 1'-4' long, short-petioled, acute or acuminate at the apex, undulate or slightly crisped, punctate, ciliate, very acrid; ocreae cylindric, fringed with short bristles, sometimes slightly pubescent, usually swollen at the base by the development of several flowers within; racemes panicled, 1'-3' long, narrow, drooping, interrupted; calyx green, 3-5-parted (usually 4-parted) conspicuously punctate; stamens 4 or sometimes 6; style short, 2-3-parted; achene lenticular or 3-angled. broadly oblong or ovoid, slightly gibbous, 1 1/4"- 11/2" long, granular, dull.
In moist waste places, almost throughout North America. Naturalized from Europe in our area, perhaps indigenous in the far Northwest. Biting-persicaria or -knotweed. Bite-tongue. Snake- or sickle-weed. Pepper-plant. Red-shanks. Red-knees. July-Sept.
P. punctatum Ell. Bot. S. C. & Ga. 1: 455. 1817. P. acre H.B.K. Nov. Gen. 2: 179. 1817. Not Lam. Persicaria punctata Small, Fl. SE. U. S. 379. 1903. Polygonum punctatum leptostachyum (Meisn.) Small,
14: 108. 1856.
Annual or perennial, glabrous or very nearly so, stem erect or ascending, rarely prostrate, simple or branched, 1°-3° long. Leaves linear-lanceolate to oblong-lanceolate, 1'-8' long, acuminate at both ends, petioled, ciliate, conspicuously punctate, acrid, the midrib often with a few scattered hairs; ocreae cylindric; falling away at maturity; fringed with long bristles; racemes terminal, narrow, erect or slightly drooping; loosely flowered, 1/2'-3' long; calyx greenish; stamens 8; style 2-3-parted to the base; achene oblong, short, thick, lenticular or 3-angled, 1"-1 1/4" long, smooth, shining.
Persicaria robustior (Small) Bicknell (Polygonum punctatum robustius Small) seems to be only a stout form of the above species with somewhat larger flowers and fruits.
Polygonum orientate L. Sp. PI. 362. 1753.
Persicaria orientalis Spach, Hist. Nat. Veg. 10: 535. 1841.
Annual, more or less hispid, stem erect, 1°-8° tall, branched. Leaves ovate or broadly oblong, 3'-12' long, petioled, acuminate at the apex, ciliate: petioles slightly winged; ocreae cylindric, loose, with or without a spreading border, ciliate; racemes panicled, oblong-cylindric, 1 -4' long, dense, drooping; flowers large for the genus; calyx dark rose-color or crimson; stamens 7, exserted; style 2-cleff to above the middle, included; stigmas large; achene orbicular or broader than long, lenticular, flat, nearly 1 1/2" in diameter, finely reticulated and rather dull.
In waste places, escaped from gardens throughout eastern North America. Native of India. Ragged-sailor. Gentleman's-cane. Aug.-Sept.