An official website of the United States government.

The .gov means it’s official.
Federal government websites always use a .gov or .mil domain. Before sharing sensitive information online, make sure you’re on a .gov or .mil site by inspecting your browser’s address (or “location”) bar.

This site is also protected by an SSL (Secure Sockets Layer) certificate that’s been signed by the U.S. government. The https:// means all transmitted data is encrypted — in other words, any information or browsing history that you provide is transmitted securely.

National Invasive Species Information Center
U.S. Department of Agriculture
Home / Terrestrial Invasives / Terrestrial Plants / St. Johnswort

St. Johnswort

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

Distribution / Maps / Survey Status

Early Detection & Distribution Mapping System (EDDMapS) - Common St. Johnswort
University of Georgia. Center for Invasive Species and Ecosystem Health.
Provides state, county, point and GIS data. Maps can be downloaded and shared.

Images

Google Images - St. Johnswort
Google.
Invasive.org - Common St. Johnswort
University of Georgia. Center for Invasive Species and Ecosystem Health.

Videos

YouTube - Montana's Noxious Weeds: St Johnswort

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
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
Partnership
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)
Global Invasive Species Database - Hypericum perforatum (herb)
IUCN. Species Survival Commission. Invasive Species Specialist Group.
Invasive Plant Atlas of the United States - Common St. Johnswort
University of Georgia. Center for Invasive Species and Ecosystem Health.
Pacific Island Ecosystems at Risk (PIER) - Hypericum perforatum
USDA. FS. Institute of Pacific Islands Forestry.
Weeds Australia - St John's Wort (Hypericum perforatum)

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

Federal Government
Exotic Species: St. Johnswort (2010)

DOI. NPS. Science of the American Southwest.

See also: Invasive Plant Species for more fact sheets
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.
Poisonous Plants - St. Johnswort
USDA. ARS. Poisonous Plant Research Laboratory.
U.S. National Plant Germplasm System - Hypericum perforatum

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

International Government
NSW WeedWise: St John's Wort
New South Wales Department of Primary Industries (Australia).
Invasive Plants: Other Invasive Plants - St. John's Wort

Business Queensland (Australia).

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

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
Academic
MontGuide - St. Johnswort: Identification, Biology, and Integrated Management (2017)
Montana State University Extension.
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
Ohio Perennial & Biennial Weed Guide - Common St. Johnswort
Ohio State University. Ohio Agricultural Research and Development Center.
St. Johnswort: Identification, Management and Control
University of Nebraska - Lincoln. Cooperative Extension.
Professional
Weed Identification - St. Johnswort
Montana Weed Control Association.

Citations

  • 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.