Weeds

Knotweed, Japanese

Asian knotweed

Knotweed, Japanese
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Japanese Knotweed is a herbaceous perennial, which grows up to 8 feet tall in shrubby clumps. The reddish stems are hollow, smooth and jointed, similar to bamboo stems, with which it is sometimes confused. It develops a deep, matted root system, with rhizomes that can grow to 30 feet or more in length. The leaf shapes are one way to distinguish between species, and are illustrated on the following page. The small, whitish to greenish flowers grow in drooping clusters from the leaf axils. Male and female flowers are borne on separate plants and flowering occurs in late summer. The plant dies back in the winter and the tall, dead, brown stems remain standing.