2020 Bob Sweatt 2018 stephen rosenthal 2020 Bob Sweatt 2018 mark kircher 2022 Mary Conway 2022 Mary Conway 2020 Julie A. Kierstead 2019 James Gonsman 2018 mark kircher 2020 Bob Sweatt 2020 Bob Sweatt 2020 Bob Sweatt 2020 Bob Sweatt 2020 Julie A. Kierstead 2008 Keir Morse
Hypericum perforatum is a perennial herb that is not native to California.
[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. (contributed 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. (contributed by Mary Ann Machi)
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Information on California plants for education, research and conservation,
with data contributed by
public and private institutions and individuals.
[web application]. 2023. Berkeley, California:The Calflora Database
[a non-profit organization].Available: