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Ceanothus sonomensis
SONOMA CEANOTHUS

Higher Taxonomy
Family: RhamnaceaeView DescriptionDichotomous Key

Common Name: BUCKTHORN FAMILY
Habit: [Perennial herb] shrub, tree, generally erect, often thorny. Leaf: simple, generally alternate, often clustered on short-shoots; stipules generally present, occasionally modified into spines; generally petioled; blade pinnate-veined or 1--5-ribbed from base. Inflorescence: cyme, panicle, umbel, or flowers 1 or clustered in axils or on short-shoots. Flower: generally bisexual, radial; hypanthium subtending, surrounding, or partly fused to ovary; sepals 4--5; petals 0, 4--5, generally clawed; stamens 0, 4--5, alternate sepals, attached to hypanthium top, each generally fitting into a petal concavity; disk (0 or) between stamens, ovary, thin to fleshy, entire or lobed, free from ovary, adherent or fused to hypanthium; ovary superior or +- inferior, chambers [1]2--4, 1--2-ovuled, style 1, stigma entire or 2--3-lobed. Fruit: capsule, drupe.
Genera In Family: 50--52 genera, 950 species: especially tropics, subtropics some cultivated (Ceanothus; Frangula; Rhamnus; Ziziphus).
eFlora Treatment Author: John O. Sawyer, Jr., except as noted
Scientific Editor: Steve Boyd, Thomas J. Rosatti.
Genus: CeanothusView DescriptionDichotomous Key

Common Name: CALIFORNIA-LILAC
Habit: Shrub, tree-like or not, generally erect or mat- to mound-like. Stem: branches generally arranged like leaves; twigs thorn-like or not, generally not angled. Leaf: alternate or opposite, some clustered on short-shoots or not, deciduous or evergreen; stipules scale-like, thin, deciduous, or knob-like, corky, thick, base persistent; blade flat or wavy, tip generally acute to obtuse, margin thick (i.e., thicker than adjacent blade) or not, rolled under or not, wavy or not, entire or gland- or sharp-toothed, glands generally dark, teeth pale, alternate blade 1--3-ribbed from base, generally thin, opposite blade 1-ribbed from base, thick, firm. Inflorescence: umbel-, raceme-, or panicle-like aggregations of few-flowered clusters, axillary or terminal; pedicels white to deep blue or pink. Flower: conspicuous, generally < 5 mm; hypanthium surrounding fleshy disk below ovary base, in fruit thick, not splitting; sepals generally 5, lance-deltate, incurved, colored like petals, persistent; petals generally 5, blade hood-like, white to deep blue or pink; stamens generally 5, opposite petals; ovary 1/2-inferior, 3-lobed, chambers 3, each 1-ovuled, styles 3. Fruit: capsule, +- spheric, generally +- 3-lobed, generally smooth, 3-ridged or not, horned or not. Seed: 3, 2--5 mm.
Species In Genus: +- 55 species: North America. Etymology: (Greek: thorny pl) Note: Hybrids common (named hybrids not recognized here), discussed in Fross & Wilken; hybrid forms do not key easily. As recircumscribed here, Ceanothus greggii A. Gray restricted to Mexico.
eFlora Treatment Author: Dieter H. Wilken

Ceanothus sonomensis J.T. Howell
NATIVE
Habit: Plant erect, +- open, < 1.5 m. Stem: ascending to erect, not rooting at nodes; twigs not angled; gray to brown. Leaf: opposite, evergreen, +- spreading; stipules knob-like; petiole < 1 mm; blade generally 5--11 mm, 2--5 mm wide, obovate to round, adaxially shiny green, glabrous, abaxially gray, minutely appressed-tomentose, especially veins, tip notched, margin thick, teeth 3--5, +- spine-like. Inflorescence: umbel-like, +- 1 cm. Flower: blue or lavender. Fruit: 4--5 mm wide; horns 2--3 mm, slender. Chromosomes: 2n=24.
Ecology: Serpentine or volcanic substrates, chaparral; Elevation: 140--600 m. Bioregional Distribution: NCoRO (Hood Mtn region, Sonoma and Napa cos.). Flowering Time: Mar--Apr Note: Occasionally confused with Ceanothus divergens.
eFlora Treatment Author: Dieter H. Wilken
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Listed on CNPS Rare Plant Inventory

Previous taxon: Ceanothus sanguineus
Next taxon: Ceanothus spinosus

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Citation for this treatment: Dieter H. Wilken 2016. Ceanothus sonomensis, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=18437, accessed on May 30, 2016.

Citation for the whole project: Jepson Flora Project (eds.) 2016. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on May 30, 2016.


Ceanothus sonomensis
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© 2015 Barry Breckling
Ceanothus sonomensis
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© 2015 Barry Breckling

More photos of Ceanothus sonomensis in CalPhotos


Geographic subdivisions for Ceanothus sonomensis:
NCoRO (Hood Mtn region, Sonoma and Napa cos.).
Markers link to CCH specimen records. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues. Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).

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Data provided by the participants of the Consortium of California Herbaria.
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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.