Thursday, October 1, 2026
After three years of targeting the floating primrose-willow, Thurston County Public Works Department staffers finally purged 1,500 pounds of the waterway-clogging plant from Chambers Lake without herbicides.
The Public Works Noxious Weeds Program team extracted the state-banned invasive species from shorelines in Lacey over three days using only hand-pulling methods.
Early season surveys revealed fewer plants than in previous years, the county said in an announcement on Monday, Nov. 25.
Staff skipped chemical treatments entirely in 2025 after deploying herbicides in only one of the past three treatment seasons.
Floating primrose-willow, also known as Ludwigia peploides, have egg-shaped leaves on reddish stems and produce bright yellow flowers. The aquatic plant originates in parts of South America and Central America, and grows along shores of slow-moving streams or lakes.
In 2023, the Washington State Department of Ecology discovered the species at Chambers Lake, marking the first detection of floating primrose-willow in Thurston County.
That same year, the Noxious Weeds Program team developed a treatment plan after working with experts from across the region and began treatment immediately.
State law requires complete removal of floating primrose-willow wherever it appears because the plant crowds out waterways, disrupts native habitats, and makes recreation areas unusable or unsafe. Sponge-like roots trap soil, and then change water flow and quality where the plant is found.
This year, early season surveys done by staff documented a decline in plant populations around the lake.
The findings prompted staff to use only manual removal rather than herbicides. Staff notified landowners around the lake through mailings before pulling plants from private shorelines.
“This project shows the dedication of the Public Works team in protecting their local environment and our community from the harm of invasive species. Keep up the good work,” said the Public Works Department in the announcement.
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HappyOlympian
A victory against invasive weeds, Hooray!
Friday, November 28, 2025 Report this
SecondOtter
Hooray! But as always, there are more weeds to tackle. Next up: Tansy ragwort, which, in the last few years, has been allowed to grow on state lands and oh, by the way, spread into privately owner property. It's just exploded. WHY the DNR allows it to grow? I don't know. I guess they think the cinnabar moth larva will eat it. Well, they will, but the but then they drop off the plant and the tansy grows more flowers. The moths aren't successful. The DNR needs to take a few lessons from the Noxious Weeds folks!
Friday, November 28, 2025 Report this
Esther
So glad to see the County avoiding the use of herbicides. A county staff report showed that chemical substances from the Long Lake area were entering deeper aquifers. I don’t want to drink herbicide contaminated water. The County should use this mechanical approach in other places as well so we don’t mess up our groundwater. All the lake management districts are using herbicides. Why not invest in a mechanical harvester for all the lakes and stop paying for toxic chemicals?
Friday, November 28, 2025 Report this
Annierae
Bravo for accomplishing this mechanically!! Aquatic herbicides should be our last resort.
Friday, November 28, 2025 Report this