Reynoutria sachalinensis

Reynoutria sachalinensis, the giant knotweed or Sakhalin knotweed, (syns. Polygonum sachalinense, Fallopia sachalinensis) is a species of Fallopia native to northeastern Asia in northern Japan (Hokkaid , Honsh ) and the far east of Russia (Sakhalin and the southern Kurile Islands). Reynoutria sachalinensis is a herbaceous perennial plant growing to 2 C4 m (79 C157 in) tall, with strong, extensively spreading rhizomes forming large clonal colonies. The leaves are some of the largest in the family, up to 15 C40 cm (6 C15.5 in) long and 10 C28 cm (4 C11 in) broad, nearly heart-shaped, with a somewhat wavy, crenate margin. The flowers are small, produced on short, dense panicles up to 10 cm (4 in) 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. Reynoutria sachalinensis has a chromosome count of 2n=44.

from Wikipedia