Japanese Knotweed was introduced into our gardens early in the 19th century. It was recommended as being suitable for wild gardens and shrubberies, but gardeners must have soon become fed up with its invasive nature and dumped it over the garden fence. It was first noted in the wild in London in 1900, and from there it has spread rapidly through Britain. Once established it is very hard to eradicate.
On a more positive note, it can act as a shelter for woodland species like Celandines, which flower and seed before the Japanese Knotweed develops in Spring. The flowers also come late in the season, and are likely to be a valuable nectar source for insects. However, conservationists are generally agreed that the harm caused by the plant to valuable wildlife habitats, especially along watercourses, outweighs these benefits.