Centaurea maculosa (spotted knapweed)

Centaurea maculosa

Photo courtesy Bob Case

Centaurea maculosa (spotted knapweed) is a biennial to short-lived perennial (family Asteraceae). It can be found in disturbed open sites, grasslands, overgrazed rangelands, roadsides and logged areas. It crowds out native species and forage for livestock, and can invade undisturbed native bunchgrass stands. An individual plant may produce as many as 40,000 seeds.

Cal-IPC Inventory rating: High

Cal-IPC Resources on Centaurea maculosa (=C. bibersteinii)

• California Invasive Plant Inventory Assessment Form (pdf) - 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 News - Articles from our quarterly newsletter. Each issue is available as a pdf. List of articles on Centaurea maculosa.
• Cal-IPC Symposium Proceedings - Presentations and papers from our annual Symposium. List of articles on Centaurea maculosa.

Cal-IPC News Articles

• O'Rourke, B. and J. Horenstein (2009). Tackling invasive plants on California Sept. of Fish & Game lands. Cal-IPC News. 17: 12.
• Donaldson, S. (2003). Fighting weeds in the Tahoe basin. CalEPPC News. 11: 7.
• Pitcairn, M. (2000). All weeds that have approved biological control agents, accidental introductions and others. CalEPPC News. 8.

Cal-IPC Symposium Proceedings

• Brucker, P. (2002). Salmon River cooperative noxious weed program. California Exotic Pest Plant Council Symposium 2002. Sacramento, CA.
• Brucker, P. (2003). Salmon River cooperative noxious weed program for 2003. California Invasive Plant Council Symposium 2003. Kings Beach, CA.
• Butler, E. and S. Britting (1998). Mapping and control of weeds in the American River Parkway. California Exotic Pest Plant Council Symposium '98. Ontario, CA.
• Carrithers, V., B. Miller, et al. (2005). Aminopyralid: A new reduced risk active ingredient for control of broadleaf invasive and noxious weeds. California Invasive Plant Council Symposium 2005. Chico, CA.
• S. R. R. (2002). Determining the effectiveness of eradicating Centaurea maculosa from the Salmon River wildland ecosystem. California Exotic Pest Plant Council Symposium 2002. Sacramento, CA.
• DiTomaso, J. M. (1995). Overview of extension non-crop weed research in California. California Exotic Pest Plant Council Symposium '95. J. Lovich, J. Randall and M. Kelly. Pacific Grove, CA.
• DiTomaso, J. M., C. Benefield, et al. (1998). Reproductive biology of yellow starthistle (Centaurea solstitialis) maximizing late season control. California Exotic Pest Plant Council Symposium '98. Ontario, CA.
• DiTomaso, J. M., G. B. Kyser, et al. (1998). Prescribed burning for control of yellow starthistle (Centaurea solstitialis) and enhanced native plant diversity. California Exotic Pest Plant Council Symposium '98. Ontario, CA.
• Rusmore, J. T. (1995). Use of fire and cutting to control yellow starthistle. California Exotic Pest Plant Council Symposium '95. M. Kelly and J. Lovich. Pacific Grove, 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, California, CA.
• Gerlach, J. D. (1997). How the west was lost: Reconstructing the invasion dynamics of yellow star-thistle and other plant invaders of western rangelands and natural areas. California Exotic Pest Plant Council Symposium '97. Concord, CA.
• Goodwin, K. (2005). Montana weed prevention areas: Partnerships for rangeland protection. California Invasive Plant Council Symposium 2005. Chico, CA.
• Kelly, M. (1998). SWAT: Special weed action teams as abassadors for education and energy. California Exotic Pest Plant Council '98 Symposium. Ontario, CA.
• Leavitt, J. R. and C. Pirosko (2002). A brief overview of the California Dept. of Food and Agriculture’s A-rated noxious weed education and eradication program. California Exotic Pest Plant Council Symposium 2002. Sacramento, CA.
• Marler, M. J. and R. M. Callaway (2000). Role of mycorrhizae in Centaurea invasions. California Exotic Pest Plant Council Symposium 2000. Concord, California, CA.
• Melbourne, B., A. Hollander, et al. (2004). Integrating ecological, social, and economic perspectives on the spread of invasive species. California Invasive Plant Council Symposium 2004. Ventura, CA.
• Norgaard, K. M. (2003). Community responses to spotted knapweed: A sociological view. California Invasive Plant Council Symposium 2003. Kings Beach, CA.
• O'Connell, R. A. (1997). Hydrilla: A case study: The state of California's noxious weed eradication programs. California Exotic Pest Plant Council Symposium '97. Concord, CA.
• O'Connell, R. A. (1999). The state of California's noxious weed eradication programs. California Exotic Pest Plant Council. Sacramento, CA.
• Pitcairn, M. (1993). Introduction and distribution of biological control agents against exotic weeds in California. California Exotic Pest Plant Symposium '93. Westlake Village, CA.
• Smith, R. L., V. F. Carrithers, et al. (2006). Managing rangeland invasive plants with Aminopyralid (MilestoneTM). Cal-IPC Symposium. Rohnert Park, 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.
• Tu, M. and J. M. Randall (2002). 2002 Red alert! New introductions and recent expansions in California. California Exotic Pest Plant Council Symposium 2002. Sacramento, CA.
• Tu, M. and J. M. Randall (2003). 2003 Cal-IPC red alert! New invasions, recent expansions, and a few others to be on the look-out For. California Invasive Plant Council Symposium 2003. Kings Beach, CA.
• Westbrooks, R. G. (1995). Federal regulatory efforts to minimize the introduction and impacts of exotic pest plants in the United States. CalEPPC Symposium '95. Asilomar, CA.
• Young, J. A. and C. D. Clements (2000). Purple starthistle seed germination. California Exotic Pest Plant Council Symposium 2000. Concord, California, CA.
• Young, J. A., C. D. Clements, et al. (2000). Purple starthistle seed germination. California Exotic Pest Plant Council Symposium 2000. M. Kelly. Ontario, CA.

Other Resources on Centaurea maculosa (=C. bibersteinii)

• USDA PLANTS database - Federal database with information on identification and distribution, and links to websites in individual states.
• Jepson Online Interchange for California Flora -Information on taxonomy, biology, and distribution from the UC Berkeley Jepson Herbarium.
• CalFlora - Distribution information by county based on submitted observations and herbarium specimens.
• The Nature Conservancy Element Stewardship Abstract - Information compiled by TNC land managers. Photos included for some species.
• Encycloweedia - Plants ratedas noxious weeds by the California Department of Food and Agriculture.
• CalPhotos - Images of plants taken mostly in California.
• Natural Resource Projects Inventory - State database with information on resource management projects throughout California. Query by the species of interest.

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