Himalayan Knotweed

Persicaria wallichii
Family Name:	Polygonaceae
Class:	B
Other Names:	bell-shaped knotweed
Why is it a noxious weed?	It grows vigorously into dense colonies that exclude native vegetation, alters natural ecosystems and is difficult to eradicate. It poses a significant threat to riparian areas, where it can survive severe floods. Small fragments can form new plants.

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Visit Washington State Noxious Weed Control Board Here