Chinese knotweed (Pleuropterus multiflorus) belongs to the Polygonaceae (the Knotweed family). It is a perennial herb that is native to central and southern China. It was introduced into Japan in Edo Era (about 250 years ago). This vine grows in mountain slopes, rock crevices, thickets in valleys, and can reach 2-4 m in height. The leaves are ovate or narrowly ovate, with entire margins. The flowers are small, white or greenish-white, produced on short panicles in June to October. The fruits are achenes. The tuberous root is called "He Shou Wu", and used as a herbal medicine.