Calflora, a 501c3 non-profit
Distribution by County   2325    
Conyza canadensis  (L.) Cronquist

(not an active name)
Canada horseweed, Canadian horseweed
Conyza canadensis is an annual herb that is native to California, and also found elsewhere in North America and beyond.
New name: Erigeron canadensis
Record Count by County

Alameda: 36 Kings: 2 Placer: 12 Sierra: 4
Alpine: 4 Lake: 5 Plumas: 43 Siskiyou: 11
Amador: 3 Lassen: 8 Riverside: 68 Solano: 16
Butte: 81 Los Angeles: 234 Sacramento: 29 Sonoma: 34
Calaveras: 9 Madera: 21 San Benito: 49 Stanislaus: 8
Colusa: 6 Marin: 78 San Bernardino: 78 Sutter: 9
Contra Costa: 37 Mariposa: 17 San Diego: 367 Tehama: 25
Del Norte: 10 Mendocino: 24 San Francisco: 38 Trinity: 2
El Dorado: 33 Merced: 17 San Joaquin: 11 Tulare: 17
Fresno: 31 Modoc: 5 San Luis Obispo: 68 Tuolumne: 4
Glenn: 7 Mono: 23 San Mateo: 68 Ventura: 134
Humboldt: 19 Monterey: 133 Santa Barbara: 169 Yolo: 12
Imperial: 5 Napa: 19 Santa Clara: 38 Yuba: 14
Inyo: 16 Nevada: 13 Santa Cruz: 56
Kern: 41 Orange: 154 Shasta: 12

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]. 2026. The Calflora Database [a non-profit organization]. Available: https://www.calflora.org/   (Accessed: 06/14/2026).