[floranorthamerica.org] Range, Rarity: Variety nipomensis occurs primarily on Nipomo Mesa and the eastern San Luis Range of southern San Luis Obispo County. R. F. Hoover (1970) regarded it as derived from hybridization between var. impressus and Ceanothus oliganthus. However, there is little evidence to indicate that populations of these two taxa overlap in geographic and ecological range. We treat var. nipomensis as part of C. impressus, based on its furrowed veins and fruit morphology. Urbanization has reduced the number of known populations to a relatively few, scattered localities. Variety nipomensis is in the Center for Plant Conservation?s National Collection of Endangered Plants. (link added by Mary Ann Machi)