Ceanothus thyrsiflorus |
Ceanothus sonomensis |
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blue blossom, blue blossom ceanothus |
Sonoma ceanothus |
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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, 0.5–1 m, often moundlike. |
Stems | erect to ascending, not rooting at nodes; branchlets gray to grayish brown, rigid, strigillose, glabrescent. |
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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 mm; blade cupped, widely obovate to suborbiculate, 5–12 × 2–10 mm, base cuneate, margins not revolute, wavy, spinose-dentate, teeth 2–4, apex widely notched; abaxial surface pale green or grayish green and glaucous, strigillose on veins, adaxial surface shiny green, glabrous. |
Inflorescences | terminal, usually racemelike, rarely paniclelike, 2.5–9 cm. |
axillary or terminal, 0.8–1.5 cm. |
Flowers | sepals, petals, and nectary usually pale to deep blue, rarely white. |
sepals, petals, and nectary blue to lavender. |
Capsules | 3–4 mm wide, weakly lobed; valves smooth, viscid, not crested. |
4–5 mm wide, usually not, sometimes weakly lobed; valves smooth, horns subapical, minute to ± prominent, erect, intermediate ridges absent. |
2n | = 24. |
= 24. |
Ceanothus thyrsiflorus |
Ceanothus sonomensis |
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Phenology | Flowering Mar–Jun. | Flowering Mar–Apr. |
Habitat | Sandy or rocky flats and slopes, maritime chaparral, open sites in mixed evergreen and conifer forests. | Sandy to rocky soils derived mostly from volcanic substrates, slopes, ridges, chaparral. |
Elevation | 10–600 m. (0–2000 ft.) | 100–700 m. (300–2300 ft.) |
Distribution |
CA; OR; Mexico (Baja California)
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CA |
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 sonomensis is distinctive in having spinose-dentate, few-toothed leaves, and slender fruit horns two to three millimeters; it occurs at a few scattered localities in the mountains of Napa and Sonoma counties. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 90. | FNA vol. 12, p. 103. |
Parent taxa | Rhamnaceae > Ceanothus > subg. Ceanothus | Rhamnaceae > Ceanothus > subg. Cerastes |
Sibling taxa | ||
Synonyms | C. thyrsiflorus var. chandleri, C. thyrsiflorus var. repens | |
Name authority | Eschscholtz: Mém. Acad. Imp. Sci. St. Pétersbourg Hist. Acad. 10: 285. (1826) — (as thyrsiflora) | J. T. Howell: Leafl. W. Bot. 2: 162. (1939) |
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