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You are here: Home / Plants / Species Profiles / St. Johnswort
Species Profiles

St. Johnswort

St. JohnswortScientific name: Hypericum perforatum L. (ITIS)

Common names: St. Johnswort, St. John's wort, common St. Johnswort, Klamath weed, common goatweed, tipton weed

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Selected Resources

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)

Impact: Crowds out native species and forage on pasturelands; toxic to livestock (Klein 2011; Zouhar 2004)

Current U.S. Distribution:


Selected Resources:

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Council or Task Force

Fact Sheet: St. John's-wort (Jan 2014; PDF | 851 KB)
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


Pacific Island Ecosystems at Risk (PIER) - Hypericum perforatum
USDA. FS. Institute of Pacific Islands Forestry.

Alaska Exotic Plants Information Clearinghouse (AKEPIC): Species Biography - Common St. Johnswort (Feb 7, 2011; PDF | 128 KB)
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).

Invasive Plant Atlas of the United States - Common St. Johnswort
University of Georgia. Center for Invasive Species and Ecosystem Health.

Global Invasive Species Database - Hypericum perforatum (herb)
IUCN. Species Survival Commission. Invasive Species Specialist Group.

Federal Government

U.S. National Plant Germplasm System - Hypericum perforatum
USDA. ARS. National Genetic Resources Program. GRIN-Global.

Poisonous Plants - St. Johnswort
USDA. ARS. Poisonous Plant Research Laboratory.

Fire Effects Information System (FEIS) - Hypericum perforatum
USDA. FS. Rocky Mountain Research Station. Fire Sciences Laboratory.

PLANTS Database - Common St. Johnswort
USDA. NRCS. National Plant Data Center.

Exotic Species: St. Johnswort (2010)
DOI. NPS. Science of the American Southwest.

See also: Invasive Plant Species for more fact sheets

International Government

Weeds in Australia - St John's Wort (Hypericum perforatum)
Australian Government. Department of the Environment and Energy.

NSW WeedWise: St John's Wort
New South Wales Department of Primary Industries (Australia).

Invasive Plants: Other Invasive Plants - St. John's Wort
Queensland Business and Industry Portal (Australia).

State Government

Encycloweedia: Data Sheet - Common St. Johnswort or Klamathweed
California Department of Food and Agriculture.
See also: Included on California's noxious weed list; see Encycloweedia: Program Details for additional resources

Noxious Weed Species - Common St. Johnswort
Colorado Department of Agriculture. Conservation Services Division. Noxious Weed Program.

Class C Noxious Weed: Common St. Johnswort
Washington State Noxious Weed Control Board.

St. Johnswort: Options for Control (PDF | 525 KB)
Lincoln County Noxious Weed Control Board (Washington).

See also: Weed I.D. and Options for Control for more species


Weed Control in Natural Areas in the Western United States: Common St. Johnswort (2013; PDF | 215 KB)
University of California. Weed Research and Information Center.
See also: Weeds in Natural Areas for more information sheets

MontGuide - St. Johnswort: Identification, Biology, and Integrated Management (2017)
Montana State University Extension.

St. Johnswort: Identification, Management and Control
University of Nebraska - Lincoln. Cooperative Extension.

Ohio Perennial & Biennial Weed Guide - Common St. Johnswort
Ohio State University. Ohio Agricultural Research and Development Center.


Weed Identification - St. Johnswort
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.

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Last Modified: Apr 13, 2018
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