Ceanothus thyrsiflorus |
Ceanothus pauciflorus |
|
---|---|---|
blue blossom, blue blossom ceanothus |
desert buckbrush, desert buckthorn, Mojave ceanothus |
|
Habit | Shrubs, sometimes arborescent, evergreen, 0.5–6 m. Stems erect, usually ascending to arcuate, rarely prostrate, not rooting at nodes; branchlets green, not thorn-tipped, angled in cross section, flexible, not tuberculate, sparsely puberulent or glabrous. | 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 3–10 mm; blade flat to cupped, elliptic to ovate, 10–40(–50) × 5–15(–20) mm, base obtuse to rounded, margins denticulate to serrulate, usually not revolute, sometimes incompletely revolute, teeth glandular, 23–48, apex obtuse, abaxial surface pale green, sparsely puberulent to villosulous or glabrate, veins prominently raised, puberulent to villosulous, adaxial surface dark green, 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 | terminal, usually racemelike, rarely paniclelike, 2.5–9 cm. |
axillary, rarely racemelike, 0.7–3 cm. |
Flowers | sepals, petals, and nectary usually pale to deep blue, rarely white. |
sepals and petals white to cream, sometimes pale blue or lavender; nectary yellowish green, brown, or blue. |
Capsules | 3–4 mm wide, weakly lobed; valves smooth, viscid, not 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 thyrsiflorus |
Ceanothus pauciflorus |
|
Phenology | Flowering Mar–Jun. | Flowering Feb–May. |
Habitat | Sandy or rocky flats and slopes, maritime chaparral, open sites in mixed evergreen and conifer forests. | Rocky slopes, ridges, alluvial fans, sagebrush and montane shrublands, pinyon and/or juniper and montane conifer woodlands. |
Elevation | 10–600 m. (0–2000 ft.) | 900–2900. |
Distribution |
CA; OR; Mexico (Baja California)
|
AZ; CA; NM; NV; TX; UT; n Mexico; c Mexico
|
Discussion | Ceanothus thyrsiflorus occurs along the coast from Coos County, Oregon, south to Santa Barbara County, California, and disjunctly near Eréndira, Baja California. A wide range of growth forms characterize this species and the closely related C. griseus, including plants ranging from almost prostrate to arborescent, sometimes with single trunks. Prostrate plants from several maritime bluffs along the California coast have been called C. thyrsiflorus var. repens McMinn; they retain their stature under cultivation. Named hybrids include C. ×regius (Jepson) McMinn (C. thyrsiflorus × C. papillosus) and C. ×vanrensselaeri Roof (C. thyrsiflorus × C. incanus). H. McMinn (1944) reported hybrids with C. foliosus. (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. 90. | FNA vol. 12, p. 107. |
Parent taxa | Rhamnaceae > Ceanothus > subg. Ceanothus | Rhamnaceae > Ceanothus > subg. Cerastes |
Sibling taxa | ||
Synonyms | C. thyrsiflorus var. chandleri, C. thyrsiflorus var. repens | C. greggii, C. greggii var. franklinii, C. vestitus |
Name authority | Eschscholtz: Mém. Acad. Imp. Sci. St. Pétersbourg Hist. Acad. 10: 285. (1826) — (as thyrsiflora) | de Candolle: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 2: 33. (1825) |
Web links |
|