NOREAS was retained by the Naval Facilities Engineering Command Southwest to survey and map approximately 4,000 acres for threatened, endangered, and rare plants on Naval Weapons Station Seal Beach Detachment Fallbrook, California (Detachment Fallbrook). In addition to the rare plant surveys the Project also includes: (1) documenting the locations of exotic/invasive species and host plants for the federally listed Quino Checkerspot Butterfly (Euphydryas editha quino), including Plantago erecta (California plantain), Antirrhinum coulterianum (white snapdragon), Plantago patagonica (woolly plantain), and Cordylanthus rigidus var. setigerus (thread-leaved bird’s beak), (2) reviewing Detachment Fallbrook’s existing Plant List and providing updates to the list based on the results of the surveys and updates to taxonomic names, (3) reviewing the existing specimen collection at Detachment Fallbrook to target missing species for collection and accessioning; and (4) collection and deposition of voucher specimens representing newly documented species or previously reported species that lack a voucher specimen for Detachment Fallbrook.