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St. Johnswort

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St. Johnswort
St. Johnswort flower, Alaska - Photo by Michael Shephard; USDA, Forest Service
Scientific Name: 
Hypericum perforatum L. (ITIS)
Common Name: 
St. Johnswort, St. John's wort, common St. Johnswort, Klamath weed, common goatweed, tipton weed
Native To: 
Eurasia and North Africa (Zouhar 2004)
Date of U.S. Introduction: 
1700s (Zouhar 2004)
Means of Introduction: 
Introduced as an ornamental and as a medicinal herb (Klein 2011)
Crowds out native species and forage on pasturelands; toxic to livestock (Klein 2011; Zouhar 2004)

Distribution / Maps / Survey Status

University of Georgia. Center for Invasive Species and Ecosystem Health.
Provides state, county, point and GIS data. Maps can be downloaded and shared.


University of Georgia. Center for Invasive Species and Ecosystem Health.


Google. YouTube; Montana Department of Agriculture.

Selected Resources

The section below contains highly relevant resources for this species, organized by source. Or, to display all related content view all resources for St. Johnswort.

Council or Task Force

Alberta Invasive Species Council (Canada).

See also: Fact Sheets for more information about individual invasive species, including those listed as "Prohibited Noxious" and "Noxious" under the Alberta Weed Control Act

University of Alaska - Anchorage. Alaska Center for Conservation Science.
See also: Non-Native Plant Species List for additional factsheets (species biographies) and species risk assessment reports of non-native species present in Alaska and also non-native species currently not recorded in Alaska (potential invasives)
IUCN. Species Survival Commission. Invasive Species Specialist Group.
University of Georgia. Center for Invasive Species and Ecosystem Health.
USDA. FS. Institute of Pacific Islands Forestry.

Centre for Invasive Species Solutions; Atlas of Living Australia; Australian Government. Department of Agriculture, Water and the Environment.

Federal Government

DOI. NPS. Science of the American Southwest.

See also: Invasive Plant Species for more fact sheets
USDA. FS. Rocky Mountain Research Station. Fire Sciences Laboratory.
USDA. NRCS. National Plant Data Center.
USDA. ARS. Poisonous Plant Research Laboratory.

USDA. ARS. National Genetic Resources Program. GRIN-Global.

International Government
New South Wales Department of Primary Industries (Australia).
State and Local Government
Washington State Noxious Weed Control Board.
California Department of Food and Agriculture.
See also: Included on California's noxious weed list; see Encycloweedia: Program Details for additional resources

Colorado Department of Agriculture. Conservation Services Division. Noxious Weed Program.

Lincoln County Noxious Weed Control Board (Washington).
See also: Weed I.D. and Options for Control for more species
University of California. Weed Research and Information Center.
See also: Weeds in Natural Areas for more information sheets

Ohio State University. Ohio Agricultural Research and Development Center.

University of Nebraska - Lincoln. Cooperative Extension.
Montana Weed Control Association.


  • Integrated Taxonomic Information System. Hypericum perforatum. [Accessed Mar 22, 2015].
  • Klein, H. 2011. Common St. Johnswort (PDF | 128 KB) University of Alaska Anchorage, Alaska Exotic Plants Information Clearinghouse.
  • Zouhar, K. 2004. Hypericum perforatum. In: Fire Effects Information System. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.