King County sounding the alarm as harmful weeds begin to grow this spring

While early spring has the welcome blooms of cherry trees, tulips and daffodils, it’s also the season when noxious weeds such as giant hogweed, poison-hemlock and garlic mustard have a growth spurt.

King County noxious weed experts are alerting homeowners and gardeners to be on the lookout for these nasty invaders, which can be a threat to people, animals and entire ecosystems.

Steven Burke, King County Noxious Weed Program manager, said giant hogweed, poison-hemlock and garlic mustard are easily spotted in the spring, and should be dealt with as soon as possible.

  • Poison-hemlock is acutely toxic if eaten by people or animals. It closely resembles a carrot plant when it is young, and can be confused with fennel and anise when it is flowering or in seed.
  • Giant hogweed can cause burns and blisters on the skin.  It shows up in urban alleys and ravines where it has spread from ornamental plantings.
  • Garlic mustard is edible for people but rapidly takes over in forests and stream banks, where it out-competes native plants and reduces habitat for local fauna.
  • Additionally, horse and cattle owners are also being urged to watch for tansy ragwort, which can cause deadly liver poisoning in animals.  Young tansy ragwort plants can be found this month and will be easy to spot later in the spring as they being to grow flowering stems.

The County’s noxious weed program is available to help residents learn to identify and control these and other harmful noxious weeds. Weed specialists will be on hand at several community events this spring and summer including Newcastle Earth Day Fair and Shoreline Earth Day Every Day Fair, both scheduled for April 20.

Details and the full schedule of noxious weed information tables for the year can be found on the County’s website. Community groups can schedule a presentation on noxious weeds or an information booth at their event by contacting education specialist Sasha Shaw, at 206-296-0290, or

Noxious weeds are non-native plants that impact natural resources, agriculture, and human health in King County or in other counties in Washington. The Washington State Noxious Weed Control Board and the county weed boards in Washington regulate the spread of noxious weeds that are harmful but not yet widespread in the state, and educate residents about those that are already too well-established to eradicate.

The list of species that property owners and public agencies are required or advised to control in King County is found on the County’s noxious weed website.

New for the 2013 King County weed list is the requirement to control invasive knotweed along the Cedar River and its tributaries, upstream of the Renton City Limits, where the community and county are working together to protect the river from this harmful invader. The County Weed Board requires control of knotweed only if there is funding available through grants or other sources for private landowners to receive knotweed control free of charge.

The King County Noxious Weed Control Board places a priority on preventing new infestations of the most serious noxious weeds, and encourages property owners to work together in stopping the spread of established noxious weeds.

Information on noxious weeds, including the King County weed list and the Washington noxious weed law can be found online at For more information on the King County Noxious Weed Board and Noxious Weed Program, call or email Burke at 206-296-0290 or


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