Reynoutria Houtt.
Large dioecious perennial herbs with stout stems, often forming clumps or thickets, with ± woody rhizomes; nodes jointed; ochreae large. Lvs cauline, broadly ovate to oblong, large; base usually truncate to cordate. Fls in axillary panicles, with rudiments of opposite sex. Perianth segments 5, accrescent, ± white, free, subequal, the outer 3 keeled and becoming winged. Stamens 8. Styles rather short, 2-3; stigmas lobed and ± fimbriate. Fr. a trigonous nut with obtuse or acute angles, spineless.
Key
c. 15 spp., temperate Asia. Naturalised spp. 2.
Reynoutria is often included in Polygonum, but Roberty, G. and Vautier, S., Boissiera 10: 56-57 (1964), accepted it at generic rank, mainly because of the rhizomatous habit and keeled perianth segments.
