Ceanothus divergens
Calistoga ceanothus
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Family: Rhamnaceae · Type: Shrub · Native
Conservation status: CNPS 1B.2
Ceanothus divergens (Calistoga ceanothus) is a native California shrub in the Rhamnaceae family, recognized by . Geographic restriction, red-brown twigs, and spine-toothed folded leaves diagnostic.
Calistoga ceanothus is a rare (CNPS 1B.2) California native shrub found in the northern Coast Ranges of Napa and Sonoma counties in volcanic slopes, chaparral, and pine/oak woodland at elevations of 150 to 950 meters. Flowering from February to April, this plant produces blue to purple flowers in compact umbel-like clusters up to 2 centimeters long. Growing as an erect or mound-like shrub 0.5 to 1.5 meters tall with ascending red-brown stems, it forms a distinctive dense and upright habit. Its opposite evergreen leaves are elliptic to narrowly obovate, 10 to 19 millimeters long, with shiny green upper surfaces and wavy margins featuring 3 to 11 spine-like teeth in the distal two-thirds. The fruit is 4 to 6 millimeters wide with slender horns 1.5 to 2.5 millimeters long.
Identification and appearance
Key characters: 32 sympatric species. Geographic restriction, red-brown twigs, and spine-toothed folded leaves diagnostic.
Habitat and range
Habitat: Volcanic slopes, chaparral, pine/oak woodland
Elevation: 150-950 m
California counties: Napa, Sonoma, Lake
Bloom period
Ceanothus divergens blooms Feb-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 divergens native to California?
Yes. Ceanothus divergens is native to California (recorded as native).
When does Ceanothus divergens bloom?
Ceanothus divergens blooms Feb-Apr.
Where in California does Ceanothus divergens grow?
Ceanothus divergens occurs in Napa, Sonoma, Lake, at elevations of 150-950 m.
What plant family does Ceanothus divergens belong to?
Ceanothus divergens is in the Rhamnaceae family, genus Ceanothus.
Is Ceanothus divergens rare or endangered?
Ceanothus divergens 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.