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Landowners: Time to control toxic tansy ragwort and keep horses, cattle safe


Toxic tansy ragwort is blooming in fields and pastures across King County, and the County’s noxious weed program can help landowners control this invasive weed that poses a serious health threat to horses, cattle sheep, and other animals.


Tansy ragwort – a plant that is toxic to horses and other livestock –rsz_county-controlling-tansy-ragwort-roadside-sshaw is now blooming across King County, and the County’s noxious weed program offers a variety of resources to help landowners control this dangerous invader. 

Known for its aggressive growth, bitter-tasting living tansy ragwort is typically avoided by animals, but it can be ingested by livestock when inadvertently cut and dried with other pasture grass for hay. 

Public and private landowners in King County are required to control infestations of tansy ragwort, and the King County Noxious Weed Program can offer advice on the best control methods for specific properties with large infestations.

“The most important action property owners can take when tansy ragwort is present is removing and killing the plants before they go to seed,” said Steven Burke, King County Noxious Weed Program manager. “A single large tansy ragwort plant can produce up to 150,000 seeds that can lie dormant in the soil for up to 15 years.”

Property owners who suspect they have a tansy ragwort infestation on their land are encouraged to alert the King County Noxious Weed Program as soon as possible.

For more information, call the noxious weed program at 206-477-9333; via email at, or by contacting Sasha Shaw, noxious weed specialist, 206-477-4824;