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Species
Information
- giant
knotweed
- Polygonum
sachalinense F.
Schmidt ex Maxim.
- USDA
Symbol: POSA4
- 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 over 12 ft tall. Closely related and similar to Japanese knotweed. Leaf cordate, or heart shaped; often exceeds 1 ft long. Inflorescence of creamy white flowers sparse, and the flower size does not increase with maturity. Hybrids with Japanese knotweed common. Japanse knotweed is smaller with truncate leaves.
Impacts:
Giant knotweed is the largest of the knotweeds, enabling this species to dominate and out compete native or beneficial plants. It poses a significant threat to riparian areas where it prevents streamside tree regeneration. Research indicates that giant knotweed produces allelochemicals from the roots, which aid in its dominance and rapid colonization. Giant knotweed is a viable pollen source for Japanese knotweed, resulting in male fertile hybrids which are often confused with Japanese knotweed.
Biological
Controls: No approved biological control agent is currently available.
Oregon
Maps of Giant Knotweed Distribution
Links:
USDA
Plants Database information on giant knotweed
GRIN
Database information on giant knotweed
Oregon Department
of Agriculture information on giant
knotweed
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