Flora of North America species comparison

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Ceanothus cordulatus

Ceanothus fresnensis

mountain whitethorn, snow bush, whitethorn ceanothus

Fresno ceanothus, Fresno mat
Habit Shrubs, evergreen, 0.5–1.5 m. Stems ascending to spreading, not rooting at nodes; branchlets yellowish or grayish green, glaucescent, thorn-tipped, round in cross section, rigid, puberulent, glabrescent. Shrubs, 0.1–0.3 m, matlike.
Stems

prostrate or spreading, rooting at proximal nodes;

branchlets brown to reddish or grayish brown, rigid, tomentulose.
Leaves

petiole 2–8 mm;

blade flat to cupped, ovate to elliptic, 10–30 × 6–18 mm, base rounded, margins usually entire, sometimes minutely glandular-denticulate distally, glands 18–30, apex obtuse, abaxial surface pale grayish green, sparsely puberulent or glabrous, sometimes villosulous along veins, adaxial surface pale green to grayish green, glaucous, dull, glabrate; 3-veined from base.

not fascicled, sometimes crowded, not obscuring internodes;

petiole 1–2 mm;

blade flat or ± cupped, elliptic to oblanceolate, 4–12 × 3–8 mm, base obtuse to rounded, margins ± thick, not revolute, usually entire, sometimes minutely denticulate near apex, teeth 0–3, apex rounded to retuse, abaxial surface pale green, strigillose, adaxial surface dark green, shiny, puberulent, glabrescent.
Inflorescences

axillary, umbel-like or racemelike, sometimes densely clustered, 1.2–2(–4) cm.

axillary, 1–2.3 cm.
Flowers

sepals, petals, and nectary usually white, rarely pink.

sepals, petals, and nectary usually blue, rarely pale blue.
Capsules

3.5–5 mm wide, lobed;

valves rugose, viscid when young, weakly crested.

4–6 mm wide, weakly lobed;

valves smooth, horns subapical, prominent, erect, intermediate ridges absent.
2n

= 24.

Ceanothus cordulatus

Ceanothus fresnensis
Phenology Flowering May–Jul. Flowering May–Jun.
Habitat Rocky ridges and slopes, chaparral, conifer and mixed evergreen forests. Granitic soils and outcrops, semishaded sites, conifer forests.
Elevation 400–3400 m. (1300–11200 ft.) 400–2200 m. (1300–7200 ft.)
Distribution
from FNA
CA; NV; OR; Mexico (Baja California)
[WildflowerSearch map]
[BONAP county map]
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
Discussion

Ceanothus cordulatus is one of the most common shrubs in montane chaparral and forests of the Coast Ranges and Cascades of southern Oregon and northern California, southward through the Sierra Nevada, Transverse and Peninsular ranges of California, to the mountains of northern Baja California, and occurs disjunctly in the Charleston Mountains of Nevada.

Putative hybrids between Ceanothus cordulatus and C. velutinus var. velutinus, reported from the Klamath Mountains, the southern Cascade Range, and the Sierra Nevada, have been called C. ×lorenzenii (Jepson) McMinn. A rare intersectional hybrid between C. cordulatus and C. prostratus in the Lake Tahoe basin has been named C. ×serrulatus McMinn. Putative hybrids of C. cordulatus with C. diversifolius and C. integerrimus also have been reported (H. McMinn 1944).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Ceanothus fresnensis occurs infrequently along the western slopes of the Sierra Nevada, from Nevada County south to Fresno County. Despite its similarity to C. arcuatus, the two species can be separated by differences in life form and intensity of flower color. Ceanothus fresnensis tends to occur in relatively dense forests, whereas C. arcuatus occurs in open, relatively exposed sites, often at higher elevations.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 12, p. 87. FNA vol. 12, p. 101.
Parent taxa Rhamnaceae > Ceanothus > subg. Ceanothus Rhamnaceae > Ceanothus > subg. Cerastes
Sibling taxa
C. americanus, C. arboreus, C. arcuatus, C. confusus, C. crassifolius, C. cuneatus, C. cyaneus, C. dentatus, C. divergens, C. diversifolius, C. fendleri, C. ferrisiae, C. foliosus, C. fresnensis, C. gloriosus, C. griseus, C. hearstiorum, C. herbaceus, C. impressus, C. incanus, C. integerrimus, C. jepsonii, C. lemmonii, C. leucodermis, C. maritimus, C. martini, C. masonii, C. megacarpus, C. microphyllus, C. oliganthus, C. ophiochilus, C. otayensis, C. palmeri, C. papillosus, C. parryi, C. parvifolius, C. pauciflorus, C. perplexans, C. pinetorum, C. prostratus, C. pumilus, C. purpureus, C. roderickii, C. sanguineus, C. sonomensis, C. spinosus, C. thyrsiflorus, C. tomentosus, C. velutinus, C. verrucosus
C. americanus, C. arboreus, C. arcuatus, C. confusus, C. cordulatus, C. crassifolius, C. cuneatus, C. cyaneus, C. dentatus, C. divergens, C. diversifolius, C. fendleri, C. ferrisiae, C. foliosus, C. gloriosus, C. griseus, C. hearstiorum, C. herbaceus, C. impressus, C. incanus, C. integerrimus, C. jepsonii, C. lemmonii, C. leucodermis, C. maritimus, C. martini, C. masonii, C. megacarpus, C. microphyllus, C. oliganthus, C. ophiochilus, C. otayensis, C. palmeri, C. papillosus, C. parryi, C. parvifolius, C. pauciflorus, C. perplexans, C. pinetorum, C. prostratus, C. pumilus, C. purpureus, C. roderickii, C. sanguineus, C. sonomensis, C. spinosus, C. thyrsiflorus, C. tomentosus, C. velutinus, C. verrucosus
Name authority Kellogg: Proc. Calif. Acad. Sci. 2: 124, fig. 39. (1863) Dudley ex Abrams: Bot. Gaz. 53: 68. (1912)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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