Hypericum perforatum

Hypericum perforatum_common St. Johnswort_flower_JM DiTomaso
Photo: Lake Tahoe Basin Weed Coordinating Group

Common names: St. John's wort; klamathweed; tipton weed; goatweed

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.

Cal-IPC Rating: Limited?

CDFA Rating: C*?


Plant Assessment Form - Information gathered by Cal-IPC on the impacts, rate of spread, and distribution of invasive plants in California. Does not include management information.

Species ID Card

Invasive Species ID Card - To support field identification of early detection species, Cal-IPC has designed a set of Species ID cards that can be downloaded, printed double-sided, and trimmed to size.

Weed Management Notes

  • Management Notes - Information on management techniques and effectiveness from the University of California Cooperative Extension’s Weed Research & Information Center.

Cal-IPC Newsletter Articles

Cal-IPC Symposium Presentations

Presentations are linked where available. Where a presentation is not available, find more information by reading the abstract in the Cal-IPC Symposia Archive.

There are no Symposium presentations associated with this species yet.

Other Hypericum perforatum Information

  • CalPhotos - Images of plants taken mostly in California.
  • Calflora - Distribution map and records of this species in California.
  • CalWeedMapper - Distribution map of this species in California with ability to determine regional priorities.
  • EDDMapS - Distribution of this species in North America.
  • Jepson Interchange - Information on this plant's taxonomy, biology, and distribution from UC Berkeley's Jepson Herbarium.
  • USDA PLANTS Database - Information on identification and distribution, with links to websites in individual states.
  • Additional photos

    Hypericum perforatum_flowers_copyright 2015_NealKramer
    Hypericum perforatum (St. John's wort) flowers. Photo: &#169 2015 Neal Kramer
    Hypericum perforatum_fruits_copyright 2015_NealKramer
    Hypericum perforatum (St. John's wort) fruits. Photo: &#169 2015 Neal Kramer
    Hypericum perforatum_leaf detail_copyright 2015_NealKramer
    Hypericum perforatum (St. John's wort) leaf detail. Photo: &#169 2015 Neal Kramer