Quick answer: 20 native California plants have a recorded bloom range that includes September.
20 species
- Apache plume Fallugia paradoxa · 6 states
- Black-eyed Susan Rudbeckia hirta · 42 states
- California bay laurel Umbellularia californica · 3 states
- California buckwheat Eriogonum fasciculatum · 2 states
- Cardinal flower Lobelia cardinalis · 37 states
- Coast redwood Sequoia sempervirens · 1 states
- Common selfheal Prunella vulgaris · 2 states
- Common yarrow Achillea millefolium · 31 states
- Creosote bush Larrea tridentata · 5 states
- Desert globemallow Sphaeralcea ambigua · 2 states
- Desert marigold Baileya multiradiata · 4 states
- Desert willow Chilopsis linearis · 4 states
- Fireweed Chamerion angustifolium · 28 states
- Honey mesquite Prosopis glandulosa · 3 states
- Jojoba Simmondsia chinensis · 2 states
- Rocky Mountain bee plant Peritoma serrulata · 22 states
- Scarlet gilia Ipomopsis aggregata · 9 states
- Shrubby cinquefoil Dasiphora fruticosa ssp. floribunda · 15 states
- Toyon Heteromeles arbutifolia · 1 states
- Wyoming Indian paintbrush Castilleja linariifolia · 4 states