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King County, Washington Noxious Weed Identification and Control

Poison Hemlock
Conium maculatum

poison hemlock leavesThis widespread Class C weed is found throughout Washington. It is acutely toxic to people and animals. In western WA, it is common on roadsides, in open fields, and in natural areas. Unrelated to the native evergreen hemlock tree, poison-hemlock can be deadly; it has gained notoriety through its use in the state execution of Socrates.

Poison-hemlock can be confused with wild carrot (Daucus carota, or Queen Anne's Lace), as with many other members of the parsley family that resemble it. While poison hemlock is similar to wild carrot, their differences are numerous. Poison-hemlock has smooth hollow stalks with purple blotches and no hairs on its stems. It can get quite tall, sometimes up to 8 feet or higher. It produces many flower heads in a more open and branching inflorescense. In contrast, wild carrot usually has one red flower in the center of the flower top and is usually about 3 feet tall, or less. Poison-hemlock starts growing in the spring time, producing flowers in late spring, while wild carrot produces flowers later in the summer.

poison hemlock flowersFor more information on identification and control of poison-hemlock, please read the Poison-hemlock Weed Alert (144 kb, Acrobat file).

Links for More Information:

Poison Hemlock Photos - click thumbnail to see larger image

poison-hemlock click for larger photo poison-hemlock click for larger photo Young poison hemlock plant - click for larger image poison-hemlock click for larger photo

 

Related Information:

Agencies


Program offices are located at 201 S. Jackson St., Suite 600, Seattle, WA 98104. To contact a staff member at the King County Noxious Weed Control Program, please call 206-296-0290 or by reach them by email.