Calflora Taxon Report
Hypericum perforatum L.
Common st. johnswort, Klamath weed, Klamathweed
Hypericum perforatum is a perennial herb that is not native to California.
Cal-IPC rating: limited
Alternate Names and Sources:
None
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Bloom Period
redone or more occurrences
within a 7.5-minute quadrangle
The blue points on the map indicate observations in Calflora.
Click on the map to view observations within a specific county.
Potential Range Plant Characteristics Location Suitability
Observations: ~5,282 records Add an Observation to Calflora Search for Hypericum perforatum
Name Status:
Accepted by: PLANTS + POWO
Calflora Category:
angiosperm
Jepson eFlora section:
eudicot
USDA PLANTS group:
Dicot
Toxicity:
Possible skin irritation from touching any part of this plant.
Wetlands:
Occurs usually in non wetlands, occasionally in wetlands
Habitat:
disturbed, disturbed
Communities:
weed, characteristic of disturbed places

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Additional Photos on Calflora
External links:
USDA Plant Profile Consortium of California Herbaria (CCH2) Integrated Taxonomic Info System (ITIS) International Plants Names Index (IPNI) Cal-IPC Profile rating: limited
CalPhotos (UC Berkeley) iNaturalist

[Wikipedia] Eurasia native: Possibly a hybrid between H. maculatum and H. attenuatum, the species can be found across temperate areas of Eurasia and has been introduced as an invasive weed to much of North and South America, as well as South Africa and Australia. While the species is harmful to livestock and can interfere with prescription drugs, it has been used in folk medicine over centuries, and remains commercially cultivated in the 21st century. (link added by Mary Ann Machi)

[Cal-IPC] Invasive: Hypericum perforatum (common St. Johnswort, klamathweed) is a perennial plant (family Clusiaceae) grown for medicinal use, but it can be toxic to light colored livestock when consumed in large quantities. By 1940, more than 1 million hectares of California were infested by St. Johnswort, but biological control agents have eliminated most populations below 1500 m elevation. (link added by Mary Ann Machi)

Suggested Citation
“Calflora - Taxon Report.” The Calflora Database, a non-profit organization. .

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