Japanese Knotweed - Fallopia japonica
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Japanese knotweed (Fallopia japonica, syn. Polygonum cuspidatum, Reynoutria japonica) is a large, herbaceous perennial plant, native to eastern Asia in Japan, China and Korea.
Japanese knotweed was first introduced to Europe and North America in the late 19th century for ornamental use, for planting to prevent soil erosion, and sometimes as a forage crop for grazing animals. Now, however, it is typically considered an invasive plant or weed where it has been introduced, and is a frequent colonizer of temperate riparian ecosystems, roadsides and waste places. It can be found in 39 of the 50 United States (PUSDA) and in six provinces in Canada. The species is also a common invader in Europe, and in the U.K. it was made illegal to spread Japanese knotweed by the Wildlife and Countryside Act 1981. In particular, the City of Swansea, South Wales has had a serious problem with it for many years. An estimated 62,000 tonnes infests the city's open spaces and cost estimates for clearing the infestation exceed £9,000,000. In the Czech republic this plant is causing serious problems, for example in national parks.
Japanese knotweed forms dense stands of stems that become impenetrable by other plants once well-established. The rapid growth of new shoots and leaves in the spring shades out any vegetation below, suppressing the growth of other plants, including established native species.
Website, video, and graphics by Rob Nelson
For more information on this plant or management please contact US Army Corp of Engineers