Fallopia japonica

Reynoutria japonica, synonyms Fallopia japonica and Polygonum cuspidatum, is a large species of herbaceous perennial plant of 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 an 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 (9.8–13.1 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 (2.8–5.5 in) long and 5–12 cm (2.0–4.7 in) broad, with an entire margin. The flowers are small, cream or white, produced in erect racemes 6–15 cm (2.4–5.9 in) long in late summer and early autumn. Related species include giant knotweed (Reynoutria sachalinensis, syns. Fallopia sachalinensis, Polygonum sachalinense) and Russian vine (Fallopia baldschuanica, Polygonum baldschuanicum). Other English names for Japanese knotweed include fleeceflower, Himalayan fleece vine, monkeyweed, monkey fungus, Hancock's curse, elephant ears, pea shooters, donkey rhubarb, sally rhubarb, Japanese bamboo, American bamboo, and Mexican bamboo. In Chinese medicine, it is known as huzhang (Chinese: 虎杖; pinyin: hǔzhàng), which translates to 'tiger stick'. There are also regional names, and it is sometimes confused with sorrel. In Japanese, the name is itadori (虎杖, イタドリ). Japanese knotweed flowers are valued by some beekeepers as an important source of nectar for honeybees, at a time of year when little else is flowering. Japanese knotweed yields a monofloral honey, usually called bamboo honey by northeastern U.S. beekeepers, like a mild-flavoured version of buckwheat honey (a related plant also in the Polygonaceae). The young stems are edible as a spring vegetable, with a flavour similar to extremely sour rhubarb. In some locations, semi-cultivating Japanese knotweed for food has been used as a means of controlling knotweed populations that invade sensitive wetland areas and drive out the native vegetation. It is eaten in Japan as sansai or wild foraged vegetable. It is used in traditional Chinese and Japanese medicine to treat various disorders through the actions of resveratrol, although there is no high-quality evidence from clinical research for any medical efficacy. Extracts of resveratrol from R. japonica roots are higher in content than those from stems or leaves, and have highest levels at the end of the growing season. The plant is known as itadori (虎杖). The kanji expression is from the Chinese meaning 'tiger stick'. One interpretation of the Japanese name is that it comes from 'remove pain' (alluding to its painkilling use), though there are other etymological explanations offered.