Polygonum cuspidatum, Reynoutria japonica, Fallopia japonica
Reynoutria japonica, synonyms Fallopia japonica and Polygonum cuspidatum, is a species of herbaceous perennial plant in the knotweed and buckwheat family Polygonaceae. It is commonly known as Asian knotweed or Japanese knotweed. It is native to East Asia in Japan, China and Korea. In North America and Europe, the species has successfully established itself in numerous habitats, and is classified as a pest and invasive species in several countries.
Japanese knotweed has hollow stems with distinct raised nodes that give it the appearance of bamboo, though it is not related. While stems may reach a maximum height of 3–4 m (10–13 ft) each growing season, it is typical to see much smaller plants in places where they sprout through cracks in the pavement or are repeatedly cut down. The leaves are broad oval with a truncated base,7–14 cm (3–5+1⁄2 in) long and5–12 cm (2–4+1⁄2 in) broad, with an entire margin. The flowers are small, cream or white, produced in erect racemes6–15 cm (2+1⁄2–6 in) long in late summer and early autumn.