Ceanothus cordulatus |
Ceanothus pauciflorus |
|
---|---|---|
mountain whitethorn, snow bush, whitethorn ceanothus |
desert buckbrush, desert buckthorn, Mojave ceanothus |
|
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, 0.2–2 m, sometimes moundlike. |
Stems | erect or weakly ascending to spreading, not rooting at nodes; branchlets light gray to ashy gray, rigid, puberulent to tomentulose, hairs curly or wavy, glabrescent. |
|
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 (0–)1–3 mm; blade flat to ± cupped, elliptic, oblong-elliptic, obovate, or suborbiculate, 5–15(–20) × 3–14(–15) mm, base cuneate to rounded, margins thick, not revolute, entire or remotely denticulate, teeth 1–5(–7), apex acute to ± truncate, abaxial surface pale green to grayish green, glabrate or puberulent, hairs curly or wavy, glabrescent, adaxial surface grayish green, puberulent, hairs curly or wavy, glabrescent. |
Inflorescences | axillary, umbel-like or racemelike, sometimes densely clustered, 1.2–2(–4) cm. |
axillary, rarely racemelike, 0.7–3 cm. |
Flowers | sepals, petals, and nectary usually white, rarely pink. |
sepals and petals white to cream, sometimes pale blue or lavender; nectary yellowish green, brown, or blue. |
Capsules | 3.5–5 mm wide, lobed; valves rugose, viscid when young, weakly crested. |
3.5–6 mm wide, not, or sometimes weakly, lobed; valves smooth, horns lateral, prominent to minute or absent, spreading, intermediate ridges absent. |
2n | = 24. |
|
Ceanothus cordulatus |
Ceanothus pauciflorus |
|
Phenology | Flowering May–Jul. | Flowering Feb–May. |
Habitat | Rocky ridges and slopes, chaparral, conifer and mixed evergreen forests. | Rocky slopes, ridges, alluvial fans, sagebrush and montane shrublands, pinyon and/or juniper and montane conifer woodlands. |
Elevation | 400–3400 m. (1300–11200 ft.) | 900–2900. |
Distribution |
CA; NV; OR; Mexico (Baja California)
|
AZ; CA; NM; NV; TX; UT; n Mexico; c Mexico
|
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 pauciflorus as circumscribed here includes plants having flat to cupped leaf blades with a sparse to dense but not intertwined indumentum composed of short curly or wavy hairs, at least when young; this indumentum also occurs on the petiole and ultimate branchlets. Such plants in the United States have been treated either as C. greggii or C. vestitus (M. Van Rensselaer and H. McMinn 1942). However, R. McVaugh (1998) and D. O. Burge and K. Zhukovsky (2013) provided evidence that they should be treated as C. pauciflorus. Specimens from the desert slopes of the Sierra Nevada and San Bernardino Mountains, California, and a few scattered localities in western Arizona, have leaves similar in shape and dentation to those of C. perplexans, suggesting local hybridization. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 87. | FNA vol. 12, p. 107. |
Parent taxa | Rhamnaceae > Ceanothus > subg. Ceanothus | Rhamnaceae > Ceanothus > subg. Cerastes |
Sibling taxa | ||
Synonyms | C. greggii, C. greggii var. franklinii, C. vestitus | |
Name authority | Kellogg: Proc. Calif. Acad. Sci. 2: 124, fig. 39. (1863) | de Candolle: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 2: 33. (1825) |
Web links |
|