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King County targeting poison-hemlock, other harmful plants on public lands to protect people and the environment


Toxic poison-hemlock joins the list of harmful plants the King County Noxious Weed Program will control on public lands and roadsides this year, and the public can help with this important work by reporting noxious weed locations via the customer service app, King County Connect.


County weed specialists were alarmed last summer to discover the toxicpoison_hemlock_vertical_2019 plant poison-hemlock growing in community gardens, parks and trails in Seattle and other cities in King County. Small poison-hemlock plants that can be mistaken for a carrot or parsley plant are deadly if eaten.

A full size poison-hemlock plant can be confused with fennel or dill, and even the seeds are highly toxic. Gardeners, wild plant foragers and children are especially at risk of accidental exposure to this plant, particularly when it grows mixed in with edible plants. Livestock can become seriously ill and even die when they consume poison-hemlock.

King County Noxious Weed Control Program employees posted multilingual signs alerting people about poison-hemlock in affected areas; educated people at community events; and notified parks and roads managers when they received reports about poison-hemlock. However, because poison-hemlock was not a regulated noxious weed, it was difficult to get all the plants controlled. 

The weed’s status changed in January, when the King County Noxious Weed Control Board selected poison-hemlock for required control on public lands and roadsides, as allowed under the Washington State Noxious Weed Law. 

Now if poison-hemlock is found growing on a roadside or public property anywhere in King County, including the cities, the noxious weed program will alert the agency in charge of that area to make sure the plants are controlled.

The public can report locations with the mobile app King County Connect or through the County’s online Report-a-Weed form. Photos of poison-hemlock and other noxious weeds are available at

On private property, poison-hemlock control isn’t required but it is strongly encouraged, especially where there is potential for exposure (such as farms, schools or gardens) or where there is a risk of plants spreading to other properties.
Because the plant is highly toxic, gloves should be worn when handling this plant, and all plant parts should be disposed of in the garbage or contained where there is no risk of spread or accidental exposure. 

Identification and control information is available on the King County website or by contacting the Noxious Weed Control Program at 206-477-9333 or

There are over 90 species of noxious weeds that state law requires property owners and public agencies to control on their properties in King County, 60 of which have been found growing in the county. 

Regulated species are mostly those found in only a few locations where there is still a chance of eradication, or those with serious potential impacts on people, farms or the environment. For the widespread noxious weeds, the county focuses on education and providing technical assistance. Noxious weed sightings can be reported to King County online.

Knowing which plants are the worst and how to control them is the specialty of King County’s noxious weed program personnel, and they are ready to teach anyone who needs or wants to know more. And if people can’t control their noxious weeds themselves but want to do the right thing, the noxious weed program will find a way to help them.

The 2019 King County Noxious Weed List spells out which noxious weeds fall under the regulated category according to the state law. The list also educates people about additional invasive plants that aren’t regulated but that are also harmful to people or impact the environment.

County residents can learn about noxious weeds by taking a free class on noxious weeds, visiting the program’s website and Noxious Weeds blog, or stopping by an information table at community events around the county. The noxious weed program also has a few specialty weed control tools for loan, such as large weed pullers for Scotch broom and injector tools for knotweed, and they offer vouchers for free disposal of regulated noxious weeds at county transfer stations. 

Learn more about the King County Noxious Weed Control Program by calling 206-477-9333 or by contacting Sasha Shaw, communication specialist for the noxious weed program, 206-477-4824, or

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The King County Noxious Weed Control Program works with county residents and public agencies to prevent and minimize harmful effects of noxious weeds to the environment, recreation, public health, and economic resources in King County. The Noxious Weed Control Program’s Board is composed of community members appointed by the King County Council. Information is available at

King County Noxious Weed Program
King County Connect

Doug Williams, 206-477-4543

About the King County Water and Land Resources Division
The Water and Land Resources Division works to protect the health and integrity of King County’s natural resources. Employees work to reduce flood risks, monitor water quality and restore wildlife habitat; manage, and reduce the harmful impacts from stormwater, noxious weeds and hazardous waste; create sustainable forestry and agriculture; and protect open space to support all of these efforts.