This is the fourth edition of the Checklist of the Vascular Plants of San Diego County (here referred to as simply the “Checklist”), which 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.)
This and previous editions of the Checklist (Simpson et al. 1995, 1996; Simpson and Rebman 2001) function to update A Flora of San Diego County, California (Beauchamp 1986). The need for this Checklist arose with the publication of The Jepson Manual: Higher Plants of California (Hickman 1993, here referred to as “The Jepson Manual”), which brought numerous nomenclatural changes to our County's flora. In addition, a great number of taxa new to the County have been discovered since the 2001 (third) edition and many misidentifications have been corrected.