Thread-leaved brodiaea is a California endangered plant species, which means that killing or possession of plants collected from the wild is prohibited by the California Endangered Species Act (CESA). This species is also listed as threatened under the federal Endangered Species Act. Thread-leaved brodiaea is a member of the brodiaea family (Themidaceae) and is a perennial bulbiferous herb. It produces several linear leaves from an underground corm, and blue to red-purple flowers on a leafless stalk. This species typically grows in herbaceous plant communities such as grassland communities, alkali playa, and in vernal pools. In some locations, thread-leaved brodiaea grows in open areas associated with coastal sage scrub. The range of this species extends from the foothills of the San Gabriel Mountains at Glendora in Los Angeles County, east to Arrowhead Hot Springs in the western foothills of the San Bernardino Mountains in San Bernardino County, and south through eastern Orange and western Riverside Counties to the City of San Diego. At the time of this webpage posting, the California Natural Diversity Database reports 103 natural occurrences of this species that are presumed to still exist.
At the time of federal listing in 1998, the U.S. Fish and Wildlife Service identified loss of habitat from urbanization and agricultural conversion as the most significant threat to thread-leaved brodiaea. Since that time, urbanization has remained the most significant threat to the species because populations occur in close proximity to heavily urbanized areas. Other threats to thread-leaved brodiaea include alteration of hydrology and impacts from livestock grazing, unauthorized off-highway vehicle activity, discing and mowing for fire suppression, and competition from nonnative plants. The dumping of livestock manure has also been identified as a threat to a few localized populations in Riverside County.
Although urbanization remains the most prominent threat to thread-leaved brodiaea, several populations of this species have been protected by regional planning efforts. Long-term conservation of thread-leaved brodiaea is dependent upon continued protection of additional existing occurrences and minimization of habitat loss caused by development. Sites with large or geographically distinct populations of this species should be acquired and protected, and nonnative plants should be controlled and managed on sites that have been set aside for conservation. Research on thread-leaved brodiaea should be conducted that focuses on pollinators and their impact on the number of new plants that are developed, soil characteristics that facilitate establishment and propagation, and germination.
CDFW has participated in the following thread-leaved brodiaea studies and projects with support from the California Endangered Species Tax Check-off Funds:
CDFW may issue permits for thread-leaved brodiaea pursuant to CESA, and you can learn more about the California laws protecting thread-leaved brodiaea and other California native plants. Populations of thread-leaved brodiaea occur in CDFW’s South Coast Region. More information is also available from the U.S. Fish and Wildlife Service Species Profile for thread-leaved brodiaea.