The flowers are small, produced on short, dense panicles up to  long in late summer or early autumn; it is gynodioecious, with male and female (male sterile) flowers on separate plants. The species is closely related to the Japanese knotweed, Reynoutria japonica, and can be distinguished from it by its larger size, and in its leaves having a heart-shaped (not straight) base and a crenate margin.
This plant produces small flowers in clusters that grow throughout late summer or early autumn; it has a unique reproductive strategy, with male and female flowers appearing on different plants. The species shares similarities with Japanese knotweed but can be identified by its larger size and distinctive leaf shape.