Flora of North America species comparison

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Ceanothus cordulatus

Ceanothus spinosus

mountain whitethorn, snow bush, whitethorn ceanothus

green-bark ceanothus, redheart
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, sometimes arborescent, evergreen, 2–6 m. Stems erect, not rooting at nodes; branchlets green, thorn-tipped or not, round to ± angled in cross section, rigid, glabrous or sparsely puberulent.
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;

petiole 4–7 mm;

blade ± cupped, elliptic to oblong, 11–35 × 8–29 mm, base cuneate to rounded, margins entire, apex obtuse to weakly retuse, abaxial surface pale green, not glaucous, sometimes puberulent on midribs, adaxial surface green, shiny, glabrous; pinnately veined.
Inflorescences

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

axillary, paniclelike, 4–17 cm.
Flowers

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

sepals, petals, and nectary pale blue to blue.
Capsules

3.5–5 mm wide, lobed;

valves rugose, viscid when young, weakly crested.

4–6 mm wide, not lobed;

valves smooth, not conspicuously viscid, not or weakly crested.
2n

= 24.

= 24.

Ceanothus cordulatus

Ceanothus spinosus
Phenology Flowering May–Jul. Flowering Jan–May.
Habitat Rocky ridges and slopes, chaparral, conifer and mixed evergreen forests. Rocky slopes, coastal sage scrub, chaparral.
Elevation 400–3400 m. (1300–11200 ft.) 60–900 m. (200–3000 ft.)
Distribution
from FNA
CA; NV; OR; Mexico (Baja California)
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; Mexico (Baja California)
[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.)

Like Ceanothus incanus, plants of C. spinosus are polymorphic for the presence of thorn-tipped branchlets. Putative hybrids with C. thyrsiflorus and C. oliganthus var. sorediatus have been reported (M. Van Rensselaer and H. McMinn 1944).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 12, p. 87. FNA vol. 12, p. 86.
Parent taxa Rhamnaceae > Ceanothus > subg. Ceanothus Rhamnaceae > Ceanothus > subg. Ceanothus
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. 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. thyrsiflorus, C. tomentosus, C. velutinus, C. verrucosus
Name authority Kellogg: Proc. Calif. Acad. Sci. 2: 124, fig. 39. (1863) Nuttall: in J. Torrey and A. Gray, Fl. N. Amer. 1: 267. (1838)
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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