Hypericum perforatum

Hypericum perforatum_common St. Johnswort_flower_JM DiTomaso
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.

Rating: Limited

Cal-IPC Resources

  • 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.
  • CalWeedMapper - Statewide maps, climate models, and reports.
  • Cal-IPC News - Our quarterly newsletter. Each issue is available as a pdf.
  • Cal-IPC Symposium Proceedings - Presentations and papers from our annual Symposium.
  • Don't Plant a Pest! - Select your region to find non-invasive alternatives to ornamental species. Also see our statewide brochure on trees.

    Other Resources

    Symposium Presentations

    • Connick, S. and M. Gerel (2004). Partnering to prevent invasions of plants of horticultural origin. California Invasive Plant Council Symposium 2004. Ventura, CA.
    • Donaldson, S., W. West, et al. (2003). Getting the job done: Working within the regulatory environment at Lake Tahoe to manage weeds. California Invasive Plant Council Symposium 2003. Kings Beach, CA.
    • Kirk, A. A., T. Widmer, et al. (2003). The potential contribution of natural enemies from Mediterranean Europe to the management of the invasive weed Arundo donax (Graminae; Arundinae) in the U.S. California Invasive Plant Council Symposium 2003. Kings Beach, CA.
    • Pitcairn, M. J. and D. M. Woods (1998). Control methods: Biological control. California Exotic Pest Plant Council Symposium '98. Ontario, CA.
    • Pitcairn, M. J. and D. M. Woods (1998). Control methods: biological control. California Exotic Pest Plant Council Symposium 1998. Ontario, CA.
    • Thomsen, C. D., W. A. Williams, et al. (1996). Yellow starthistle management with grazing, mowing, and competitive plantings. California Exotic Pest Plant Council Symposium '96. San Diego, CA.

    Cal-IPC News Articles

    • Anonymous(1995). Biological control of invasive exotic pest plant species: A report on the importance of maintaining and enhancing our nation's biological control capabilities. CalEPPC News. 3: 6-10.
    • Connick, S. and M. Gerel (2005). Don't sell a pest: A new partnership to prevent plant invasions through horticulture. Cal-IPC News. 13: 4-5,14.
    • Donaldson, S. (2003). Fighting weeds in the Tahoe basin. CalEPPC News. 11: 7.
    • Hoekstra, B. (1997). Klamathweed. CalEPPC News. 5: 9.
    • Pitcairn, M. (2000). All weeds that have approved biological control agents, accidental introductions and others. CalEPPC News. 8.