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Japanese Knotweed (Polygonum cuspidatum)       



Japanese knotweed


Brad Bluemer, Bonner County Weed Superintendent, stands in front of Japanese knotweed which can grow over 10 feet tall.
Brad Bluemer, Bonner County Weed Superintendent, stands in front of Japanese knotweed which can grow over 10 feet tall.

A member of the family Polygonaceae, 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 9-13 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, 3–6 inches long and 2-5 inches broad, with an entire margin. The flowers are small, creamy white, produced in erect racemes 2-6 inches long in late summer and early autumn.

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. It is sometimes considered an invasive species or weed. It 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 common in Europe. In the U.K. it was made illegal to spread Japanese knotweed by the Wildlife and Countryside Act 1981, and is listed by the World Conservation Union as one of the world's 100 worst invasive species. In the U.S.A. it is listed as an invasive weed in Ohio, Vermont, Virginia, Washington and now Idaho. (From Wikipedia)

The zig zag stem is one identifying feature of Japanese knotweed.
The zig zag stem is one identifying feature of Japanese knotweed.

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