4. Reynoutria Houttuyn, Nat. Hist. 2(8): 639. 1777.
虎杖属 hu zhang shu
Li Anjen (李安仁 Li An-ren); Chong-wook Park
Herbs perennial, dioecious. Rhizomes thickened. Stems erect, stout, hollow. Leaves simple, alternate, petiolate; leaf blade ovate or ovate-elliptic, margin entire; ocrea oblique. Inflorescence axillary, paniculate. Flowers unisexual. Perianth persistent, 5-parted; outer 3 tepals accrescent and winged on abaxial surface in female flowers. Stamens 8. Styles 3; stigmas fimbriate. Achenes ovoid, trigonous.
About two species: Asia; one species in China.
One of us (Park) believes that this group should be included within the genus Fallopia (see Ronse Decraene & Akeroyd, Bot. J. Linn. Soc. 98: 321–371. 1988; and Bailey & Stace, Pl. Syst. Evol. 180: 29–52. 1992).
The hybrid Reynoutria japonica × R. sachalinensis (R. ×bohemica) is probably cultivated and probably also escaped in China.