イタドリ, スカンポ, メイゲツソウ 【虎杖, スカンポ, 明月草】
Japanese knotweed (Polygonum cuspidatum, Fallopia japonica)
■ イタドリ (Polygonum cuspidatum), of the buckwheat family (Polygonaceae, タデ科), is native to Eastern Asia and grows wild throughout Japan. It is a vigorous, rhizomatous perennial and has tall, jointed stems with a reddish tinge near the base that can grow to 3 metres high in one season, and large, broadly oval, alternate leaves. In late summer it produces panicles of small white or occasionally red flowers.
□ イタドリ is a plant of many names.
In Japan イタドリ is often called スカンポ, although, confusingly, there is another plant that goes by this name (スイバ or sorrel, Rumex acetosa L.). It also has numerous other regional names, which include スッポン, イタンポ, カッポン and イヌガラシ. The red-flowered variety of the same plant is called メイゲツソウ.
In English, this plant is most commonly called the Japanese knotweed, although it is also known as the Japanese bamboo, Mexican bamboo, Japanese fleece flower, donkey rhubarb, crimson beauty (red form) and Hancock's curse.
Furthermore, this plant has been given many scientific names, three of which are commonly used: Polygonum cuspidatum Sieb. & Zucc., Reynoutria japonica Houtt. and Fallopia japonica (Houtt.) Ronse Decraene.
This plant also has a Jekyll-and-Hyde split personality.
In Japan, イタドリ is a wild spring vegetable (山菜 さんさい) that can be served boiled, fried or raw. Often children pick young shoots while walking, skin them and eat the juicy, acid-tasting inside.
イタドリ is also a medicinal herb, and its name is thought to mean 痛取り or 疼取り, or painkiller. Young leaves are applied to cuts and grazes to stop bleeding and ease pain. In Chinese medicine, the rhizome of this plant is called 虎杖根 (huzhang) and used to treat scalds.
Information on cooking the Japanese knotweed: Here and here.
Japanese knotweed as a medicinal herb: Here.
The dark side of this plant became apparent, however, when it made its way to the West. The Japanese knotweed was introduced in Britain and North America in the 19th century as an ornamental garden plant. It quickly escaped gardens and ran wild, forming dense, impenetrable thickets on stream banks, roadsides and open grounds, suffocating native plants along the way. Interestingly, it is a dioecious plant and requires both male and female plants in order to reproduce, and only the female form was taken to Europe. Still, it has proved to be an extremely rampant spreader, with its rhizomes capable of reaching several metres. It can regrow from small rhizome fragments, which makes it a very difficult weed to control and gives it the reputation as one of the most troublesome "alien invaders" in temperate Europe and North America.
Home page of the British Japanese Knotweed Alliance
From the US Plant Conservation Alliance's alien plant information page
This entry was created by Yuno Hanlon.