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Taxon  Report  
Ambrosia trifida  L.
Giant ragweed
Ambrosia trifida is an annual herb that is not native to California.
There is a high risk of this plant becoming invasive in California according to Cal-IPC.
Siskiyou Del Norte Modoc Humboldt Shasta Lassen Trinity Plumas Tehama Butte Mendocino Glenn Sierra Yuba Lake Nevada Colusa Placer Sutter El Dorado Yolo Alpine Napa Sonoma Sacramento Mono Amador Solano Calaveras Tuolumne San Joaquin Marin Contra Costa Alameda Santa Cruz Mariposa Madera San Francisco San Mateo Merced Fresno Stanislaus Santa Clara Inyo San Benito Tulare Kings Monterey San Bernardino San Luis Obispo Kern Santa Barbara Ventura Los Angeles Riverside Orange San Diego Imperial
Observation Search
~17 records in California
redone or more occurrences
within a 7.5-minute quadrangle

Bloom Period
Genus: Ambrosia
Family: Asteraceae  
Category: angiosperm  
PLANTS group:Dicot
Jepson eFlora section: eudicot

Wetlands: Equally likely to occur in wetlands and non wetlands

Habitat: disturbed

Communities: wetland-riparian, weed, characteristic of disturbed places

Name Status:
Accepted by JEF + PLANTS

Information about  Ambrosia trifida from other sources

[Cal-IPC] Origins: Ambrosia trifida (giant ragweed) is native to the central and eastern United States. (link added by Jessica Johnston)

[CDFA] Introduction: Worldwide Distribution: Native to eastern North America. Giant ragweed has been introduced to, and is now established in western North America and much of Asia and Europe. Official Control: Giant ragweed is listed as a noxious weed in at least three states (California, Delaware, and Illinois). California Distribution: Giant ragweed has been reported in 10 California counties (Contra Costa, Glenn, Orange, Los Angeles, Madera, Monterey, San Diego, San Joaquin, San Luis Obispo, and Siskiyou). Most of these records are from residential gardens. According to one source, it is not naturalized in California, but occurs as a waif and/or garden escape. California Interceptions: Recent collections from 2011 through 2014 originated from gardens or as seed contaminants intercepted at the CA border. It is commonly intercepted in feed seed shipments entering the state. (link added by Jessica Johnston)

Suggested Citation
Calflora: Information on California plants for education, research and conservation, with data contributed by public and private institutions and individuals. [web application]. 2024. Berkeley, California: The Calflora Database [a non-profit organization]. Available: https://www.calflora.org/   (Accessed: 07/21/2024).