Japanese Knotweed
Genus: Polygonum
Species: cuspidatum
Description: Perennial that resembles bamboo and forms large clumps 1-3 meters (3-10 ft) high. Flowers are greenish-white and appear in summer.
Where it grows: Spreads primarily in along riverbanks and grows in wetlands, waste places and roadways.
How it spreads: Rhizome (underground stem) pieces are spread in fill dirt and water. Because even small fragments of a knotweed plant can sprout and form new colonies, knotweed reproduces very effectively along streams.
What it threatens: Its early growth period and height combine to shade out other vegetation and prohibit regeneration of other species. It reduces species diversity and damages wildlife habitat.
Control: Knotweed is very difficult to control and doing so generally takes several years. While new or very small patches may be eliminated through repeated digging and cutting, established patches require treatment with herbicide. All cut or dug parts of the plant must be disposed of in the garbage to prevent further spread.
More information: 4 County Cooperative Weed Management Association
Disclaimer - Clean Water Services does not endorse or recommend specific herbicides for use in controlling these species. To protect water quality, always follow herbicide label directions and obey application laws when using any herbicide.
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