Currently in print, the fourth edition of the Checklist of Vascular Plants of San Diego County catalogs all native and naturalized vascular plants known to occur in San Diego County, California, U.S.A. (Note that "naturalized" refers to non-native plants that grow, persist, and reproduce in natural, non-cultivated habitats.)
The Botany Department has compiled some localized floristic studies in our region. If you are looking for the most up-to-date collections information you may want to try the searching or mapping tools found on the San Diego County Plant Atlas website.