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Aquatic Weed Management Program in 2020

Seattle Parks and Recreation (SPR) will continue the integrated weed management program at selected lakefront properties on Lake Washington starting in early June and lasting through August 2020. This project is achieving comprehensive control of the most prevalent aquatic weeds including Eurasian milfoil, fragrant water lily, purple loosestrife, and garden loosestrife.

Controlling these weeds improves water quality and recreational access and safety at freshwater beaches, swim areas, moorages and other high-use recreation locations along the lake. This weed control creates a more natural, aesthetically appealing environment that nourishes native plant growth and aquatic species with the proper water temperature and oxygen level.

The weed control will be accomplished through application of an aquatic herbicide. This use is permitted by Washington Department of Ecology (Ecology). These herbicides have been screened and endorsed by Ecology as an effective solution to control these noxious and invasive weeds.

SPR has contracted with AquaTechnex, LLC to apply the selected non-glyphosate aquatic herbicides along the shore of Lake Washington at the following locations:

  • Matthews Park beach
  • Magnuson Park beach
  • Magnuson Park boat ramp
  • Madison Park beach
  • Madrona Park beach
  • Stan Sayers Pits
  • Lakewood Marina
  • Seward Park beach
  • Pritchard Island Beach

Informational signs will be posted near the treatment locations prior to treating the plants and appropriate safety precautions will be taken to ensure that there will be no exposure to park visitors, pets, and wildlife.  AquaTechnex, LLC will manage this online website for the project  For more information contact Patti Bakker at To learn more about the products used see