Calflora, a 501c3 non-profit
Distribution by County   1504    
Carduus pycnocephalus  L.
Italian thistle
Carduus pycnocephalus is an annual herb that is not native to California.
Cal-IPC rating: moderate
Record Count by County

Alameda: 367 Los Angeles: 622 San Benito: 197 Solano: 108
Amador: 30 Madera: 104 San Bernardino: 53 Sonoma: 422
Butte: 69 Marin: 1127 San Diego: 892 Stanislaus: 41
Calaveras: 89 Mariposa: 754 San Francisco: 211 Sutter: 21
Colusa: 24 Mendocino: 68 San Joaquin: 365 Tehama: 21
Contra Costa: 381 Merced: 37 San Luis Obispo: 135 Trinity: 23
Del Norte: 1 Monterey: 276 San Mateo: 819 Tulare: 612
El Dorado: 76 Napa: 72 Santa Barbara: 156 Tuolumne: 1006
Fresno: 103 Nevada: 79 Santa Clara: 958 Ventura: 240
Glenn: 12 Orange: 1338 Santa Cruz: 332 Yolo: 48
Humboldt: 36 Placer: 40 Shasta: 23 Yuba: 107
Kern: 145 Riverside: 58 Sierra: 1
Lake: 27 Sacramento: 429 Siskiyou: 7

Suggested Citation
Calflora: Information on California plants for education, research and conservation, with data contributed by public and private institutions and individuals, including the Consortium of California Herbaria. [web application]. 2025. The Calflora Database [a non-profit organization]. Available: https://www.calflora.org/   (Accessed: 11/15/2025).