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Species
Information
- Himalayan
knotweed (cultivated knotweed)
- Polygonum
polystachyum Wall. ex Meisn.
- USDA
Symbol: POPO5
- Oregon
Noxious Weed Designation: B, T
- Pictures
ALERT: PLEASE CALL 1-866-INVADER IF YOU SUSPECT YOU HAVE FOUND THIS SPECIES
Identification:
Perennial; blooms July to October. Grows to 6 ft tall. Closely related to giant and Japanese knotweeds. Leaves lanceolate and 4 to 8 inches long, unlike Japanese and giant knotweeds which are ovate and cordate, respectively.
Impacts:
This species is the least common of the three weedy knotweed species in the PNW. Plants grow vigorously and create dense colonies that exclude native vegetation, but they are much shorter than related species and seem less adaptable to dense shade. Established populations are persistent and difficult to eradicate due to their proximety to streams. It poses a significant threat to riparian areas, where it uses flood events for its dispersal by rapidly colonizing scoured shores and islands.
Biological
Controls: No approved biological control agent is currently available.
Oregon
Maps of Himalayan Knotweed Distribution
Links:
USDA
Plants Database information on
Himalayan
knotweed
GRIN
Database information on Himalayan
knotweed
Oregon Department
of Agriculture information on Himalayan
knotweed
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