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Aquatic Weed Management Program in 2024 

Seattle Parks and Recreation (SPR) will continue the integrated weed management program at selected lakefront properties on Lake Washington starting in late June and lasting through August 2024. This project is achieving comprehensive control of the most prevalent aquatic weeds in 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. 

Hand cutting, and manual removal of the weeds will continue as in past years. SPR will complement this work by using selected aquatic herbicides. 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 
  • Madison Park beach 
  • Madrona Park beach 
  • Mt. Baker Beach 
  • Stan Sayers Pits 
  • Seward Park beach 
  • Prichard 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.  

The work is being performed under a permit from the Washington State Department of Ecology. AquaTechnex, LLC will manage an online webpage with information and updates on the program. Information here.

For more information, please contact Bridget Kelsh  For information about aquatic noxious weed control permits visit: