Himalayan Knotweed

Persicaria wallichii


Himalayan Knotweed - A clumping perennial with hollow stems and creeping rhizomes. It grows about 6 feet in height.

Leaves: Leaf shape is elongated compared to other knotweeds and are around 5-12 inches in length. They are leathery and alternate along the stem.

Flowers: Flowers bloom from July-October. Whiteish pink flowers that are fragrant grow at the tips of branches.

Habitat: Grows in disturbed, moist sites like roadsides, riparian, and wetland areas.

Weed Classification: B Designate

Why is it a Noxious Weed?

This plant vigorously grows into dense stands that overtake native vegetation and alter ecosystems. It can survive severe floods and spread plant fragments making it difficult to eradicate.

Himalayan Knotweed is found in Lewis County but can be confused with other plants. If you think you have Himalayan Knotweed on your property, please let us know!

Control Recommendations:

WA State Noxious Weed Board

PNW Pest Management Handbook

UC Davis Weed Report