Fact Sheet: St. John's-wort (Jan 2014; PDF | 851 KB)
Alberta Invasive Plants Council (Canada).
Pacific Island Ecosystems at Risk (PIER) - Hypericum perforatum
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
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.
Germplasm Resources Information Network (GRIN) - Hypericum perforatum
USDA. ARS. National Genetic Resources Program.
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.
DOI. BLM. Arcata Field Office.
Weeds in Australia -
St John's Wort (Hypericum perforatum)
Australian Government. Department of the Environment.
Profile: St John's wort
New South Wales Department of Primary Industries
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.
Noxious Weed Species - Common St. Johnswort
Colorado Department of Agriculture. Conservation Services Division. Noxious Weed Program.
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.
Species Fact Sheet: St. Johnswort (2010; PDF | 362 KB)
Learning Center of the American Southwest.
Weed Identification - St. Johnswort
Montana Weed Control Association.