The political boundaries of California contain 4,839 native vascular plant species. An estimated 3,488 of these occur within the California Floristic Province. The state flora as a whole includes 99 ferns and fern relatives, 60 gymnosperms (53 conifers), 823 monocots, and 3862 dicots.
The largest family in this flora is the Asteraceae with 627 native species, followed by the Fabaceae with 297 species and the Poaceae with 251species. The largest five genera make up more than 10% of this total and include Carex (131 species, Cyperaceae), Eriogonum (112 species, Polygonaceae), Astragalus (94 species, Fabaceae), Phacelia (93 species, Hydrophyllaceae), and Lupinus (71 species, Fabaceae). All of these genera comprises largely of herbaceous perennial and annual species. Notable speciation has also occurred in two shrub lineages, Arctostaphylos (Ericaceae) and Ceanothus (Rhamnaceae), in response to adaptations to postfire regeneration (Raven and Axelrod, 1978).
Endemism at the species level is relatively high at 61% within the California Floristic Province. Fifty-two genera are strictly endemic to this province. If another 14 genera that extend only slightly outside of the region into Arizona or Baja California are included, then 8.1% of the genera are endemic. This high level of endemism is heavily influenced by the diversity of annual plants that comprise 27.4% of the vascular plants of the California floristic province. For annual species alone, endemism is 65.3%.
The highest species richness of MTEs in California for small plots appears to occur in lightly disturbed grasslands and oak woodlands, where 47–64 species have been reported in 0.1 ha sites. These levels of diversity at this 0.1 ha scale are also matched in postfire stands of chaparral where annual plant diversity is very high. Mature chaparral, however, exhibits very low levels of species diversity.