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Stems are green with reddish nodes, become tough and woody with age, and appear reddish-brown in the winter. Knotweed grows quickly and has hollow, bamboo-like stems that form dense leafy thickets.Leaves are simple, alternate, up to 6 inches long by 4 inches wide, and broadly ovate with pointed tips and a square base.Japanese knotweed is a shrub-like, semi-woody perennial growing up to 9 feet tall.Japanese knotweed hybridizes with giant knotweed to form the Bohemian knotweed species. Japanese knotweed plants in Europe and North America are known to be clones of a single female plant. Japanese knotweed escaped cultivation, overtook desirable vegetation and was recognized as a problem by the early 1900s. In the late 1800s, it was brought to the United States and was planted in gardens and used for erosion control along roadways and embankments. It was prized and planted in many famous gardens. Japanese knotweed is native to eastern Asia and was imported to England in the mid-1800s as an ornamental. View Minnesota Noxious Weed Law for more information. Failure to comply may result in enforcement action by the county or local municipality. Additionally, no transportation, propagation, or sale of these plants is allowed. Chrtek & Chrtkova, Zika & Jacobson)Įfforts must be made to prevent seed maturation and dispersal of plants into new areas. Schmidt ex Maxim.) Bohemian knotweed ( Polygonum x bohemicum (J. Related Species: Giant knotweed ( Polygonum sachalinense F. Scientific Names: Polygonum cuspidatum Siebold & Zucc., synonym Fallopia japonica (Houtt.) Ronse Decr. Alternate Names: Japanese bamboo, Mexican bamboo, Japanese fleece flower, crimson beauty, Reynoutria, Hancock’s curse