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St. Johnswort

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)

St. Johnswort
Image use policy

St. Johnswort flower, Alaska


Photo by Michael Shephard; USDA, Forest Service

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Distribution / Maps / Survey Status


Selected Resources

The section below contains highly relevant resources for this species, organized by source.

Council or Task Force
  • Fact Sheet: St. John's-wort [PDF, 851 KB]

    • Jan 2014
    • 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

Federal Government
International Government
State and Local Government
  • Integrated Taxonomic Information System. Hypericum perforatum. [Accessed Sep 25, 2023].

  • 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.