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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)

Impacts: 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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Fact Sheet: St. John's-wort (Jan 2014; PDF | 851 KB)
Alberta Invasive Plants Council (Canada).


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

Alaska Exotic Plants Information Clearinghouse: Species Biography - Common St. Johnswort (Feb 7, 2011; PDF | 128 KB)
University of Alaska - Anchorage. Alaska Natural Heritage Program.

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)
World Conservation Union. Invasive Species Specialist Group.


Hypericum perforatum L. (Klamath Weed) - Noxious and Nuisance Plant Management Information System (PMIS)
DOD. USACE. Engineer Research and Development Center. Environmental Laboratory.

Germplasm Resources Information Network (GRIN) - Hypericum perforatum
USDA. ARS. National Genetic Resources Program.

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.

Klamath Weed
DOI. BLM. Arcata Field Office.

Guide to Weeds in British Columbia - St. John's-wort
British Columbia Ministry of Agriculture, Food, and Fisheries (Canada).

Weed Profile: St John's wort
New South Wales Department of Primary Industries (Australia).

Pest Plant Risk Assessment - St. John's Wort (Aug 2008; PDF | 211 KB)
Queensland Department of Primary Industries and Fisheries (Australia). Biosecurity Queensland.


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

Common St. Johnswort Identification and Management (Aug 2009; PDF | 1.18 MB)
Colorado Department of Agriculture. Conservation Services Division.

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).


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.

St. Johnswort: Identification, Biology, and Integrated Management (Aug 2009; PDF | 643 KB)
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: Nov 21, 2015
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