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1. How do invasive knotweeds degrade riparian habitat?

Knotweed replaces native vegetation, depletes available LWD, contributes to slump erosion of riverbanks, interrupts nutrient cycling and impacts soil health. For more information about these, please visit the Degradation page.

2. Where did knotweed come from?

Knotweed is native to volcanic regions of Asia and was introduced into the United States originally as an ornamental plant. It is believed to have arrived in Washington State around 1930.

3. How does it spread?

After winter/spring flooding, knotweed fragments are spread downstream, allowing new knotweed plants to establish themselves. View photos of knotweed.