Flora of North America species comparison

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Ceanothus cordulatus

Ceanothus ophiochilus

mountain whitethorn, snow bush, whitethorn ceanothus

Vail Lake ceanothus
Habit Shrubs, evergreen, 0.5–1.5 m. Shrubs, 1–2 m.
Stems

ascending to spreading, not rooting at nodes;

branchlets yellowish or grayish green, glaucescent, thorn-tipped, round in cross section, rigid, puberulent, glabrescent.

erect to ascending, not rooting at nodes;

branchlets reddish brown to gray, terete, ± flexible to rigid, glabrate.
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.

both fascicled and not fascicled on same plant;

petiole 0–1 mm;

blade folded lengthwise abaxially, narrowly oblanceolate to narrowly obovate, 3–7 × 1–3 mm, base cuneate, margins not revolute, usually entire, rarely denticulate near apex, teeth 1–4, apex obtuse, rounded, or cuspidate, abaxial surface pale green, glabrate, adaxial surface pale to yellowish green, glabrate.
Inflorescences

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

axillary or terminal, 0.7–2 cm.
Flowers

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

sepals, petals, and nectary pale blue or pink-tinged.
Capsules

3.5–5 mm wide, lobed;

valves rugose, viscid when young, weakly crested.

3–4 mm wide, not lobed;

valves smooth, horns minute or absent, intermediate ridges absent.
2n

= 24.

Ceanothus cordulatus

Ceanothus ophiochilus
Phenology Flowering May–Jul. Flowering Mar–Apr.
Habitat Rocky ridges and slopes, chaparral, conifer and mixed evergreen forests. Rocky soils from deeply weathered gabbro or pyroxene substrates, slopes and ridges, chaparral.
Elevation 400–3400 m. [1300–11200 ft.] 600–700 m. [2000–2300 ft.]
Distribution
from FNA
CA; NV; OR; Mexico (Baja California)
[WildflowerSearch map]
[BONAP county map]
from FNA
CA
[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 ophiochilus, known only from the northern part of the Palomar Mountains in southwestern Riverside County, is distinctive by having small, more or less terete, fascicled leaves; it is known to hybridize with C. crassifolius at one locality.

Ceanothus ophiochilus is in the Center for Plant Conservation’s National Collection of Endangered Plants.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 12, p. 87. FNA vol. 12, p. 108.
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. 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. 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) S. Boyd: T. S. Ross & Arnseth, Phytologia 70: 29, figs. 1–4. (1991)
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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