Federal Government
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
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