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..
Perennial, often large, many-stemmed herbs with wide-spreading rootstocks, the very stout stems hollow. Leaves alternate, broad, commonly large, usually truncate or cordate at the base, petioled. Ocreae oblique, fugacious as in Rnmex, Flowers numerous, in short, axillary, sessile or nearly sessile panicles with short spreading branches. Sepals mostly 5, pale, usually white, enveloping the achene, the 3 outer ones winged at maturity, the wings firm. Stamens 6-8, included; filaments slender. Styles 3, short, distinct. Achenes 3-angled, much shorter than the sepal-wings. [Greek, referring to the calyx-wings.]
About 4 species, natives of eastern Asia. Type species: Pleuropterus cordatus Turcz. = Polygonum multiflorum Thunb.
Polygonum cuspidatum Sieb. & Zucc. Fl. Jap. Fam. Nat.
1: 158. pl. 66. 1895.
Perennial, glabrous, more or less scurfy, stem stout, erect, woody below, terete or slightly angled, much branched, 4°-8° tall. Leaves oblong-ovate or ovate-lanceolate, petioled, 2'-6' long, acuminate-cuspidate at the apex, truncate or subcordate at the base, reticulate-veined on both surfaces, their margins undulate; ocreae oblique, smooth, fugacious; racemes mostly terminal, panicled, 2'-4' long, or axillary, many-flowered, more or less pubescent; flowers greenish-white, long-pedicelled; outer segments of the 5-parted calyx very broadly winged in fruit; stamens 8; style 3-parted; achene 3-angled, narrowly oblong or oblong-pyramidal, 1 1/4"-1 1/2" long, black, smooth, shining.
Escaped from cultivation locally throughout our range. Native of Japan. July-Oct.