Introduced from the mountainous regions of Japan, Taiwan, Korea, and eastern China. To 2 m tall . Leaves are consumed as a pot herb in its native range. Introduced from the Himalayan region of south central Asia. Closely related to and can hybridize with Japanese knotweed .
Plants appear to have allelopathic properties.
Introduced from mountains of Japan and Sakhalin Islands. Stalk bases fused and sheathing. Main stems erect, often arched near top, simple to minimally branched, grooved, thick, hollow , weakly woody, swollen at nodes, usually reddish-brown at maturity. Twigs often zigzag slightly from node to node. Tips acute to acuminate.