Ceanothus decornutus
Nicasio ceanothus, Nicasio Ceanothus
(c) Alexander Wentworth, some rights reserved (CC BY) · licence
Family: Rhamnaceae · Type: Shrub · Native
Conservation status: CNPS 1B.2
Ceanothus decornutus (Nicasio ceanothus) is a native California shrub in the Rhamnaceae family, recognized by . Serpentine habitat, spine-toothed folded leaves, and granular fruits diagnostic.
Nicasio ceanothus is a rare (CNPS 1B.2) California native shrub found in western Marin County in the San Francisco Bay Area on open, rocky serpentine slopes and ridges at elevations of 50 to 290 meters. Flowering from March to April, this plant produces light blue to white flowers, sometimes with pink hues, in small umbel-like clusters 1 to 2.5 centimeters long. Growing as an erect or mound-like shrub less than 1.5 meters tall with intricately branched, thick brown stems, it develops a distinctive growth form with dense, intricate branching. Its opposite, evergreen leaves are ovate to oblong ovate, 10 to 20 millimeters long, dark green on top, with wavy margins featuring 7 to 9 spine-like teeth. The fruit is a 5 to 7 millimeter wide, 3-ridged structure with thick, rounded horns up to 2 millimeters long.
Identification and appearance
Key characters: 25 sympatric species. Serpentine habitat, spine-toothed folded leaves, and granular fruits diagnostic.
Habitat and range
Habitat: open, rocky serpentine slopes and ridges
Elevation: 50-290 m
Bloom period
Ceanothus decornutus 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 decornutus native to California?
Yes. Ceanothus decornutus is native to California (recorded as native).
When does Ceanothus decornutus bloom?
Ceanothus decornutus blooms Mar-Apr.
What plant family does Ceanothus decornutus belong to?
Ceanothus decornutus is in the Rhamnaceae family, genus Ceanothus.
Is Ceanothus decornutus rare or endangered?
Ceanothus decornutus carries California Rare Plant Rank 1B.2, state rank S1.
What habitat does Ceanothus decornutus grow in?
Ceanothus decornutus grows in open, rocky serpentine slopes and ridges.
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 2026-09-30
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.