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
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.
Cal-IPC Newsletter Articles
- Weed biological control agents approved for California. Pitcairn, Michael J.; Smith, Lincoln; Moran, Patrick. Vol 22, Issue 1
- Don’t sell a pest: A new partnership to prevent plant invasions through horticulture. Connick, Sarah; Gerel, Mike. Vol 13, Issue 2
- Fighting weeds in the Tahoe basin. Donaldson, Sue. Vol 11, Issue 2
- Klamathweed. Hoekstra, Bud. Vol 05, Issue 4
- Biological control of invasive exotic pest plant species: A report on the importance of maintaining and enhancing our nation’s biological control capabilities. CalEPPC. Vol 03, Issue 3
Cal-IPC 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.
Other Hypericum perforatum Information
- CalPhotos - Images of plants taken mostly in California.
- CalFlora - Distribution information based on submitted observations and herbarium specimens.
- CalWeedMapper - Distribution information with ability to determine regional priorities.
- Jepson Online Interchange for California Flora - Information on taxonomy, biology, and distribution from UC Berkeley's Jepson Herbarium.
- USDA PLANTS Database - Federal database with information on identification and distribution, and links to websites in individual states.