Cultivated Knotweed

A highly variable taxon; usually several varieties are recognized on the basis of degree of pubescence and size of the leaves. However, in our area the variation seems to be ± continuous.

Erect, 30-100 cm high, branched shrubby perennial. Stem, glabrous to pubescent with short internodes. Leaves 2-15 x 0.5-3.5 cm, oblong-lanceolate, acuminate, base cordate-truncate, hairy on veins, glabrous above sparsely to densely tomentose beneath, subsessile to petiolate. Ochrea tube-like, dark brown 1-2 cm long, membranous. Inflorescence thyrsoid panicles, spreading, pubescent, large with reddish axis. Ochreolae pubescent, ovate, acuminate c. 2 x c. 1.5 mm, pubescent. Flowers 3-5 mm across, very fragrant, pedicel 2-3.5 mm long, selender, jointed. Tepals 5, biseriate, white-cream coloured, unequal, inner ± broadly obovate-spathulate, obtuse, 3-3.5 (-4) mm long, outer 2, oblong, acute, smaller than the inner ones. Stamens 7-8, unequal. Ovary trigonous with 3, free styles and capitate stigma. Nuts trigonous, 3-3.5 x 1.5 mm, shining.

Distribution: Afghanistan(?), Himalayas (India, Pakistan), Xizang, N. Myanmar and Western China.

Fl. Per.: June-September.

Grows on rocks, slopes, slightly drier places between 1500-3000 m.

Polygonum polystachyum Wall. ex Meisn. in Wall., Pl. As. Rar. 3: 61. 1832; Hook. f., Fl. Brit. Ind. 5: 50. 1886, including var. glabrum and var. pubescens Wall. ex Meisn. l.c.; Webb & Chater in Tutin et al., Fl. Europ. 1: 80. 1964; R.R.Stewart, Ann. Cat. Vasc. Pl. W. Pak. & Kashm. 208. 1972; Bhopal & Chaudhri in Pak. Syst. 1: 71. 1977; Persicaria polystachya (Wall. ex Meisn.) H. Gross in B. Jahrb. 49: 315. 1913; Hara in Fl. E. Himal. 73. 1966; in Hara et al., Enum. Fl. Pl. Nepal 3: 177. 1982; Aconogonon polystachyum (Meisn.) Haradson in Symb. Bot. Upsal. 22(2): 69. 1978; Grierson & D.G.Long, Fl. Bhutan 1(1): 162. 1983; Pleuropteropyrum polystachyum (Wall. ex Meisn.) Munshi & Javeid, Syst. Stud. Polygon. Kashm. Himal. 78. 1986.