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Common St. Johnswort identification and control: Hypericum perforatum

Common St. Johnswort identification and control

Hypericum perforatum

st. johnswort flowers
This species should not be confused with the ornamental St. Johnswort found in gardens. Common St. Johnswort is taller and less dense, with smaller flowers and smaller leaves. Usually found along roadsides and in empty lots in western Washington, this weedy species can also be found in natural areas and pastures. In eastern Washington and in other regions of the western United States, common St. Johnswort is widespread and difficult to control.

Legal status in King County, Washington

Common St. Johnswort is a Class C noxious weed on the Washington State Noxious Weed List. It is on the Non-Regulated Noxious Weed List for King County, Washington. Control of Common St. Johnswort in King County is recommended but not required. For more information on noxious weed regulations and definitions, see Noxious weed lists and laws.

The King County Noxious Weed Control Board encourages property owners to remove Common St. Johnswort where possible and to avoid introducing it to new landscapes.

Additional information on common St. Johnswort

What to do if you find this plant in King County, Washington

Because Common St. Johnswort is so widespread, property owners in King County are not required to control it and we are not generally tracking infestations. We can provide advice on how to control Common St. Johnswort, but there is generally no legal requirement to do so.

Common St. Johnswort photos

st. johnswort leaves
st. johnswort leaves
st. johnswort biocontrol

Related information

Related agencies

Program offices are located at 201 S. Jackson St., Suite 600, Seattle, WA 98104. To contact staff, see the Noxious Weed Control Program Directory, send an email, or call 206-477-WEED (206-477-9333).