About the Program


Since the spring of 2010, the Pierce Conservation District has been leading knotweed eradication efforts within both the Nisqually and South Prairie Creek Watersheds.

Knotweed can affect the health of an ecosystem by competing with and crowding out native vegetation, reducing nutrient inputs which can negatively affect aquatic food webs, contributing to erosion of lands, and destroying prime habitat for local fish and wildlife. Since knotweed's primary form of distribution is through root and stem fragmentation, the flowing waters of rivers, creeks and streams serve as prime candidates for its dispersal.
A creek with overgrown vegetation and a log laying across it
Believed to have arrived in Washington State around the 1930's, knotweed has become widely established along many of our local waterways and are causing detrimental effects on local riparian and wetland habitats.
  1. How do invasive knotweeds degrade riparian habitat?
  2. Where did knotweed come from?
  3. How does it spread?
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More Information

  1. Current Research (PDF)
  2. PCD Knotweed Brochure (PDF)
  3. Streamside Planting Guide (PDF)
  4. Washington State Noxious Weed List (PDF)