Japanese Knotweed Information


Knotweed (Polygonum cuspidatum) is an herbaceous perennial that belongs to the buckwheat family (Polygonaceae). Also called Japanese fleece flower and Mexican bamboo, knotweed is an invasive plant native to Japan, Korea and China.


Japanese knotwood has a woody appearance and ovate or oblong leaves. Knotweed bears green-white or cream-colored flowers that bloom in August and September.


Japanese knotweed grows up to 10 feet in height. The rhizomes, or underground stems, reach up to 65 feet in length.


Japanese knotweed primarily spreads and produces new plants with its long, stout rhizomes. This plant also produces winged fruits that the wind can carry for a distance.


In the United States (US), Japanese knotweed has sprouted up from South Dakota to Oklahoma and from Maine to Georgia. It has invaded all of the New England states as well as some of the western states, including as California, Oregon and Washington.


Japanese knotweed thrives in locations with excess moisture and full sunlight, such as wetlands and riparian areas.


Japanese knotweed has a devastating effect on sensitive ecosystems because it crowds out native flora and the associated fauna. Knotweed also has an economical impact since it is costly to repair structural damage caused by the plant.


  • Japanese Knotweed
  • Japanese Knotweed Information
  • About Japanese Knotweed

Who Can Help

  • Japanese Knotweed Alliance
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About this Author

Cat Carson has been a writer, editor and researcher for more than 10 years. She has professional experience in a variety of media, including the Internet, newspapers, newsletters and magazines. Her work has appeared on various websites. Carson holds master’s degrees in both writing and cultural anthropology, and is currently working toward her doctorate degree.