IPM1021, New December 2003
Japanese knotweed is an escaped ornamental plant that can quickly form dense clumps in which no other vegetation can survive. The plant regenerates from rhizomes and reaches heights up to 6 feet, which gives it a shrublike appearance. Some refer to the weed as Japanese or Mexican bamboo because of its hollow and jointed stems.
Like other members of the Polygonaceae (smartweed) family, papery sheathlike ocreas are found along its stems where the leaves join. Leaves occur alternately along the reddish stems and range in size from 3 to 6 inches in length; their shape is broadly ovate. Leaf veins have a distinct red color. Flowers are produced in clusters in the leaf axils and are a white color.
After frost, the stems of the plant persist through the winter.
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