St. Johnswort

Scientific name: Hypericum perforatum L.

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

Native To: Eurasia

Date of U.S. Introduction: 1700s

Images: Invasive.org and Google

Means of Introduction: Ornamental

Impact: Crowds out native species; toxic to livestock

Current U.S. Distribution:

• PLANTS Database map (see complete PLANTS Profile for county distribution and native status)
• Early Detection & Distribution Mapping System (county distribution for Southeastern States)

Management Plans: Plants

Selected Internet Resources:

• Federal Government
• State Government
• University/Academic
• International
• Organizations

Hypericum perforatum
Integrated Taxonomic Information System.
Taxonomy

Hypericum perforatum L. (Klamath Weed) - Noxious and Nuisance Plant Management Information System (PMIS)
United States Army Corps of Engineers. Engineer Research and Development Center. Environmental Laboratory.
Identification/Description; Photographs; Introduction History; Impacts; Distribution; Controls

Hypericum perforatum Article Citation Search - AGRICOLA Database
USDA. National Agricultural Library.
Research; Special Note: NAL Catalog Search (resources)

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

St. Johnswort
USDA. ARS. Poisonous Plant Research Laboratory.
Identification/Description; Photographs; Impacts; Habitat; Distribution; Controls

Klamath Weed or St. Johnswort - Poisonous Plants
USDA. Idaho Panhandle National Forests.
Identification/Description; Photographs; Impacts

Common St. John's Wort - Weed of the Week (Jan 8, 2007; PDF | 80 KB)
USDA. FS. Northeastern Area. Forest Health Protection.
Identification/Description; Photographs; Introduction History; Impacts; Habitat; Distribution; Controls

Wanted: Dead - St. Johnswort
USDA. Forest Service. Pacific Northwest Research Station. Blue Mountains Natural Resources Institute.
Identification/Description; Photographs; Impacts; Controls

Hypericum perforatum - Fire Effects Information System (FEIS)
USDA. Forest Service. Rocky Mountain Research Station. Fire Sciences Laboratory.
Taxonomy; Identification/Description; Introduction History; Impacts; Life Cycle; Habitat; Distribution; Controls; Special Note: References

Noxious Weed: Common St. Johns-wort
USDA. Sawtooth National Forest.
Identification/Description; Controls

Plant Profile for Hypericum perforatum - PLANTS Database
USDA. NRCS. National Plant Data Center.
Taxonomy; Photographs; Distribution; Legal Aspects

Hypericum perforatum L. - An Assessment of Exotic Plant Species of Rocky Mountain National Park
DOI. Northern Prairie Wildlife Research Center.
Impacts; Life Cycle; Distribution; Controls

Klamath Weed
California Bureau of Land Management. Arcata Field Office.
Identification/Description; Photographs; Impacts; Habitat; Distribution

Common St. Johnswort or Klamathweed - EncycloWeedia
California Department of Food and Agriculture.
Identification/Description; Photographs; Introduction History; Impacts; Habitat; Life Cycle; Distribution; Dispersion; Controls

St. Johnswort
State of Colorado. Larimer County. Weed Control District.
Identification/Description; Photographs; Impacts

Weeds: St. Johnswort
Oregon Department of Agriculture. Plant Division.
Identification/Description; Photographs; Introduction History; Impacts; Habitat; Distribution; Controls; Legal Aspects

Saint Johnswort
Washington State Noxious Weed Control Board.
Identification/Description; Photographs; Introduction History; Impacts; Life Cycle; Habitat; Distribution; Controls

Hypericum perforatum L. - Wisconsin Botanical Information System
Wisconsin State Herbarium; University of Wisconsin-Madison.
Taxonomy; Photographs; Distribution

Common St. Johnswort - Invasive Plant Species of Alaska (PDF | 72 KB)
University of Alaska - Anchorage. Alaska Natural Heritage Program.
Identification/Description; Photographs; Impacts; Life Cycle; Distribution; Dispersion; Controls

Common St. Johnswort, Klamath Weed - Indiana Plants Poisonous to Livestock and Pets
Purdue University. Cooperative Extension Service.
Identification/Description; Photographs; Illustrations; Impacts; Habitat; Controls

St. Johnswort: Ill and ?Cure
Montana State University. Communication Services.
Identification/Description; Introduction History; Impacts; Habitat; Distribution; Controls

St. Johnswort (Jul 2002; PDF | 453 KB)
Montana State University. Extension Service.
Identification/Description; Illustrations; Introduction History; Impacts; Habitat; Distribution; Controls

St. Johnswort: Identification, Management and Control
University of Nebraska - Lincoln. Cooperative Extension.
Identification/Description; Photographs; Impacts; Controls

Klamath Weed Wanted Poster--Dead, Not Alive! (PDF | 37 KB)
University of Nevada - Reno. Cooperative Extension.
Identification/Description; Photographs

Managing Common St. Johnswort (PDF | 332 KB)
University of Nevada - Reno. Cooperative Extension.
Identification/Description; Photographs; Impacts; Habitat; Controls

Common St. Johnswort - Ohio Perennial & Biennial Weed Guide
Ohio State University. Ohio Agricultural Research and Development Center.
Identification/Description; Photographs; Habitat; Distribution

St. John's-wort - Guide to Weeds in British Columbia
British Columbia Ministry of Agriculture, Food, and Fisheries (Canada).
Identification/Description; Photographs; Impacts; Distribution

St. John's wort - Best Practice Management Guide for Environmental Weeds (PDF | 502 KB)
Cooperative Research Centre for Australian Weed Management.
Identification/Description; Photographs; Introduction History; Impacts; Habitat; Distribution; Dispersion; Controls; Legal Aspects

St. John's wort - Integrated Weed Management (PDF | 153 KB)
Cooperative Research Centre for Australian Weed Management.
Photographs; Impacts; Distribution; Controls

Hypericum perforatum (herb) - ISSG Global Invasive Species Database
World Conservation Union. Invasive Species Specialist Group.
Taxonomy; Identification/Description; Photographs; Impacts; Life Cycle; Habitat; Distribution; Controls

St. John's Wort
Invasive.org.
Photographs

St. Johnswort
Montana War on Weeds.
Identification/Description; Photographs; Impacts; Life Cycle; Controls

Hypericum perforatum (Klamathweed, St. John's Wort)
Nature Conservancy. Global Invasive Species Initiative.
Photographs