Source: California Invasive Plant Council
URL of this page: http://www.cal-ipc.org/ip/management/plant_profiles/Onopordum_acanthium.php
Onopordum acanthium (Scotch thistle)
Scotch thistle flower head and winged spiny stem
Onopordum acanthium (Scotch thistle) is a biennial or short-lived perennial (family Asteraceae) which is primarily found in the northeastern regions of California. Severe infestations can form tall, dense, impenetrable stands, especially in fertile soils. Onopordum acanthium reproduces only by seeds, which can germinate year round, and it is drought resistant. Infestations can reduce forage and impede movement for livestock and wildlife.
Cal-IPC Inventory rating: High
Cal-IPC Resources on Onopordum acanthium
- California Invasive Plant Inventory 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 - Articles from our quarterly newsletter. Each issue is available as a pdf. List of articles on Onopordum acanthium.
- Cal-IPC Symposium Proceedings - Presentations and papers from our annual Symposium. List of articles on Onopordum acanthium.
Cal-IPC News Articles
- Brusati, E., D. Morawitz, et al. (2011). Prioritizing Regional Response to Invasive Plants in the Sierra Nevada. Cal-IPC News. 19: 4, 5, 10.
- Richardson, B. (2004). The A-rated north. Cal-IPC News. 12: 4-5,14.
- 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
- 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.
- O'Connell, R. A. (1999). The state of California's noxious weed eradication programs. California Exotic Pest Plant Council. Sacramento, CA.
- Carrithers, V. F. (1997). Using Transline* herbicide to control invasive plants. California Exotic Pest Plant Council Symposium '97. Concord, 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.
Other Resources on Onopordum acanthium
- 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 rated as 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.