Ceanothus sonomensis
Sonoma ceanothus
(c) Ken-ichi Ueda, some rights reserved (CC BY), uploaded by Ken-ichi Ueda · licence
Family: Rhamnaceae · Type: Shrub · Native
Conservation status: CNPS 1B.2
Ceanothus sonomensis (Sonoma ceanothus) is a native California shrub in the Rhamnaceae family, recognized by notched leaf tips and very restricted geographic range.
Sonoma ceanothus is a rare (CNPS 1B.2) California native shrub found in the northern Coast Ranges in the Hood Mountain region of Sonoma and Napa counties, growing on serpentine or volcanic substrates in chaparral at elevations of 140 to 600 meters. Flowering from March to April, this plant produces blue or lavender flowers in compact umbel-like clusters about 1 centimeter wide. Growing as an erect and somewhat open shrub less than 1.5 meters tall, it has ascending stems ranging from gray to brown with distinctive twigs. Its evergreen leaves are small and obovate, approximately 5 to 11 millimeters long, with a shiny green upper surface and gray, minutely tomentose underside, featuring 3 to 5 small spine-like teeth at the notched tip. The fruit is approximately 4 to 5 millimeters wide with two to three millimeter slender horns.
Identification and appearance
Key characters: 29 sympatric species; key features are notched leaf tips and very restricted geographic range
Habitat and range
Habitat: Serpentine or volcanic substrates, chaparral
Elevation: 140-600 m
California counties: Sonoma, Napa
Bloom period
Ceanothus sonomensis blooms Mar-Apr.
Conservation status
CNPS 1B.2
How to tell it apart
vs Rhamnus: Ceanothus has showy blue/white/pink flowers in dense clusters; Rhamnus has tiny inconspicuous greenish flowers.; vs Quercus: Ceanothus has showy flower clusters and small leaves; Quercus has acorns and distinctive lobed or toothed oak leaves.; vs Baccharis: Ceanothus has individual flowers with 5 separate petals; Baccharis has composite flower heads with tiny disc flowers.; vs Cercocarpus: Ceanothus has blue/white/pink flowers in clusters; Cercocarpus has tiny flowers with no petals and feathery fruiting tails.; vs Adenostoma: Ceanothus flowers have 5 distinct colored petals; Adenostoma has tiny white flowers and needle-like clustered leaves.
Frequently asked questions
Is Ceanothus sonomensis native to California?
Yes. Ceanothus sonomensis is native to California (recorded as native).
When does Ceanothus sonomensis bloom?
Ceanothus sonomensis blooms Mar-Apr.
Where in California does Ceanothus sonomensis grow?
Ceanothus sonomensis occurs in Sonoma, Napa, at elevations of 140-600 m.
What plant family does Ceanothus sonomensis belong to?
Ceanothus sonomensis is in the Rhamnaceae family, genus Ceanothus.
Is Ceanothus sonomensis rare or endangered?
Ceanothus sonomensis carries California Rare Plant Rank 1B.2, state rank S2.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · CNPS Rare Plant Inventory · Index of California Plant Names · CalPhotos · CDFW CNDDB
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.