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 an 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: © 2015 Neal Kramer
    Hypericum perforatum_fruits_copyright 2015_NealKramer
    Hypericum perforatum (St. John's wort) fruits. Photo: © 2015 Neal Kramer
    Hypericum perforatum_leaf detail_copyright 2015_NealKramer
    Hypericum perforatum (St. John's wort) leaf detail. Photo: © 2015 Neal Kramer