| | 1. Leaves alternate, generally thin, evergreen or deciduous, stomata on lower surface not in cavities; stipules thin, deciduous; inflorescence raceme- or panicle-like; fruit without horns but often with crests or ridges (Sect. Ceanothus) |
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| | 2. Leaf generally 3-ribbed from blade base (if not, basal vein-pair more prominent than others) |
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| | 3. Twigs rigid, generally thorny; leaf glaucous; branches generally gray |
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| | 4. Plant ascending, < 1.5 m; leaf < 3 cm; generally > 1000 m |
| C. cordulatus |
| | 4' Plant erect, > 1.5 m; leaf 1.5–6 cm; < 1800 m |
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| | 5. Leaf 2.5–6 cm; fruit warty, not sticky; Klamath Ranges, Outer North Coast Ranges, San Francisco Bay Area; < 900 m |
| C. incanus |
| | 5' Leaf 1.5–4 cm; fruit sticky, not warty; Sierra Nevada Foothills, San Francisco Bay Area, South Coast Ranges, Western Transverse Ranges, San Bernardino Mountains, San Jacinto Mountains, Peninsular Ranges, n Baja California; < 1800 m |
| C. leucodermis |
| | 3' Twigs flexible, generally not thorny; leaf not glaucous; branches generally not gray |
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| | 6. Leaf entire, ± deciduous |
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| | 7. Leaf generally > 2 cm; plant erect, < 4 m; inflorescence < 15 cm; flower generally white or blue; fruit sticky, valve crests minute |
| 2 C. integerrimus |
| | 7' Leaf generally < 2 cm; plant ascending, < 1.2 m; inflorescence < 7 cm; flower pale to deep blue; fruit not sticky, valve crests ± 0 |
| 2 C. parvifolius |
| | 6' Leaf variously toothed, deciduous or evergreen |
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| | 8. Leaves deciduous; twigs glabrous; flower white |
| C. sanguineus |
| | 8' Leaves evergreen; twigs variously hairy; flower white or pale to dark blue |
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| | 9. Flower white — twigs puberulent, becoming smooth, brown; leaf aromatic, upper surface ± shiny, glabrous |
| C. velutinus |
| | 10. Leaf lower surface light green, glabrous; near coast |
| var. hookeri |
| | 10' Leaf lower surface gray, canescent; inland |
| var. velutinus |
| | 9' Flower generally pale to dark blue, rarely ± white |
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| | 11. Twigs round, not striate |
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| | 12. Leaf lower surface tomentose |
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| | 13. Leaf 3–8 cm, margin serrate, few-gland-toothed or not; twigs brown, with soft, short hairs; plant < 7 m; Channel Islands |
| C. arboreus |
| | 13' Leaf 1.5–3 cm, margin gland-toothed; twigs ± rusty-tomentose; plant < 3 m; mainland |
| 2 C. tomentosus |
| | 12' Leaf lower surface ± hairy, especially on veins, but not tomentose |
| C. oliganthus |
| | 14. Twigs ± red-brown, hairy; leaf upper surface hairy; inflorescence generally interrupted, < 5 cm; fruit lobed, crested, hairy or not; South Coast Ranges, Transverse Ranges, Peninsular Ranges; < 1300 m |
| var. oliganthus |
| | 14' Twigs generally gray-green, ± glabrous to puberulent; leaf upper surface ± glabrous; inflorescence continuous, < 4 cm; fruit barely lobed or crested, glabrous; generally coastal Transverse Ranges to North Coast Ranges; < 1000 m |
| var. sorediatus |
| | 11' Twigs angled, striate |
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| | 15. Leaf margin turned under |
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| | 16. Leaf blade ovate, lower surface gray-green, short-tomentose; inflorescence continuous, < 5 cm; fruit sticky when young, at maturity black, shiny |
| C. griseus |
| | 16' Leaf blade oblong to elliptic, lower surface pale green, densely cobwebby; inflorescence interrupted, < 15 cm; fruit not sticky when young, at maturity not shiny, not black |
| 2 C. parryi |
| | 15' Leaf margin not or only slightly turned under |
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| | 17. Leaf lower surface veins not raised; fruit not glandular-sticky; Peninsular Ranges |
| C. cyaneus |
| | 17' Leaf lower surface veins very raised; fruit glandular-sticky; Northwestern California, Central Western California |
| C. thyrsiflorus |
| | 2' Leaf generally 1-ribbed from blade base, basal vein-pair more prominent than others or not |
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| | 18. Leaf entire or rarely minutely toothed, ± glabrous |
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| | 19. Leaves evergreen, thick, rarely minutely toothed |
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| | 20. Flower white; fruit 5–7 mm, valves glandular-crested; plant < 3.5 m; branches gray-green to red-brown |
| C. palmeri |
| | 20' Flower pale blue to ± white; fruit 4–5 mm, valves barely crested; plant < 6 m; branches olive-green |
| C. spinosus |
| | 19' Leaves ± deciduous, thin, entire or rarely minutely toothed toward tip |
| |
| | 21. Leaf generally > 2 cm; plant erect, < 4 m; inflorescence < 15 cm, clusters generally stalked; flower generally white or blue; fruit sticky, valves minutely crested |
| 2 C. integerrimus |
| | 21' Leaf generally < 2 cm; plant ascending, < 1.2 m; inflorescence < 7 cm, clusters generally sessile; flower pale to deep blue; fruit not sticky, valves not crested |
| 2 C. parvifolius |
| | 18' Leaf generally toothed, at least lower surface generally hairy |
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| | 22. Leaf margin ± turned under |
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| | 23. Leaf upper surface glandular-papillate, margin minutely gland-toothed |
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| | 24. Plant ± prostrate; twigs angled, lower side gray-tomentose — coastal, grassy hills; Central Coast |
| C. hearstiorum |
| | 24' Plant ascending to erect; twigs round, generally densely hairy |
| C. papillosus |
| | 25. Plant ascending to erect, < 5 m; leaf blade 1–2 cm wide |
| var. papillosus |
| | 25' Plant ± ascending, < 1.8 m; leaf blade < 1 cm wide |
| var. roweanus |
| | 23' Leaf upper surface glabrous or hairy, rarely glandular-papillate, margin gland-toothed or not |
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| | 26. Twigs angled, tomentose; leaf upper surface not furrowed on veins, glabrous, margin not gland-toothed; inflorescence < 15 cm |
| 2 C. parryi |
| | 26' Twigs round, variously hairy; leaf upper surface furrowed on veins, puberulent, margin generally gland-toothed; inflorescence < 4 cm — stems ascending |
| |
| | 27. Leaf linear or narrowly oblong to elliptic, tip truncate to notched, upper surface rarely glandular-papillate; plant densely branched, < 1.5 m; inflorescence < 3 cm |
| C. dentatus |
| | 27' Leaf ovate to round, tip not truncate or notched, upper surface not glandular-papillate; plant moderately branched, generally < 3.5 m; inflorescence < 4 cm |
| C. impressus |
| | 22' Leaf margin not turned under |
| |
| | 28. Plant < 0.3 m, forming mat; leaf shape variable on single plants, upper surface blue-green |
| C. diversifolius |
| | 28' Plant < 3 m, ascending to erect, not forming mat; leaves ± constant in shape on individual plants, not blue-green |
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| | 29. Plant < 3 m; twigs gray-brown to reddish, rusty-tomentose, not glandular; inflorescence panicle-like; immature fruit sticky |
| 2 C. tomentosus |
| | 29' Plant < 2 m; twigs gray or pale green, generally glandular, not rusty-tomentose; inflorescence ± raceme-like; immature fruit not sticky |
| |
| | 30. Twigs gray, glandular-hairy or not; petiole < 8 mm; leaf blade upper surface dull green; flower pale blue; plant ascending, < 1 m — c Sierra Nevada Foothills to Cascade Range Foothills, Inner North Coast Ranges |
| C. lemmonii |
| | 30' Twigs pale green, glandular-hairy; petiole < 3 mm; leaf blade upper surface generally dark green; flower blue; plant ascending to erect, generally < 2 m |
| C. foliosus |
| | 31. Leaf blade upper surface ± glabrous, lower glabrous to densely hairy; plant ascending, generally < 1 m; Outer North Coast Ranges, San Francisco Bay Area, Peninsular Ranges |
| var. foliosus |
| | 31' Leaf blade upper and lower surfaces hairy; plant ascending or erect, < 2 m; Outer North Coast Ranges, San Francisco Bay Area, South Coast Ranges |
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| | 32. Leaf blade upper surface dull green, glandular-hairy, lower gray, densely hairy throughout; plant erect, < 2 m; San Francisco Bay Area, South Coast Ranges |
| var. medius |
| | 32' Leaf blade upper surface dark green, sparse-hairy, lower pale green, sparse-hairy on veins; plant ascending, < 0.8 m; Outer North Coast Ranges |
| var. vineatus |
| | 1' Leaves generally opposite (at least some alternate in C. verrucosus, C. megacarpus), thick, evergreen, stomata on lower surface in cavities; stipules thick, at least bases persistent, generally corky; inflorescence raceme-like; fruit generally with horns, with intervening ridges or not (Sect. Cerastes) |
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| | 33. Leaves on single plant alternate or alternate and opposite |
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| | 34. Leaves alternate, blades round to deltate-obovate; fruit generally 5 mm wide — South Coast (San Diego Co.) |
| C. verrucosus |
| | 34' Leaves on single plant alternate and sometimes opposite, blades elliptic to obovate; fruit 8–12 mm wide |
| C. megacarpus |
| | 35. Leaves generally opposite, < 4 cm; fruit horns 0 or minute; Channel Islands |
| var. insularis |
| | 35' Leaves generally alternate, < 2.6 cm; fruit horns prominent; Central Coast, Outer South Coast Ranges, s Channel Islands |
| var. megacarpus |
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| | 36. Flower generally white |
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| | 37. Leaf blade lower surface canescent to tomentose throughout, margin generally turned under — twigs white to rusty-tomentose |
| C. crassifolius |
| | 37' Leaf blade lower surface ± sparse-hairy on veins, canescent between, margin generally not turned under |
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| | 38. Leaf upper surface (in our vars.) generally ± cupped |
| C. greggii |
| | 39. Leaf < 2 cm, blade round or broad-elliptic to -obovate, upper surface yellow-green, margin sharp-toothed, generally near tip, or entire |
| var. perplexans |
| | 39' Leaf < 1.5 cm, blade elliptic-ovate to oblanceolate, upper surface gray-green, margin entire to toothed |
| var. vestitus |
| | 38' Leaf upper surface generally flat or ± folded lengthwise |
| |
| | 40. Leaf blade margin entire, upper surface dull green, flat; twigs glabrous; fruit 4–6 mm, horns slender or minute — flower sometimes pale blue to lavender |
| 2 C. cuneatus var. cuneatus |
| | 40' Leaf blade margin generally toothed, upper surface dark- or yellow-green, folded or flat; twigs puberulent; fruit 6–9 mm, horns not slender, not minute |
| |
| | 41. Leaf blade upper surface dark-green, generally flat; twigs rusty-puberulent; fruit 6–9 mm, horns rough; San Francisco Bay Area |
| C. ferrisiae |
| | 41' Leaf blade upper surface yellow-green, ± folded lengthwise; twigs gray-brown, puberulent; fruit ± 6 mm, horns wrinkled; Inner North Coast Ranges, High North Coast Ranges |
| C. jepsonii var. albiflorus |
| | 36' Flower blue, lavender, or pale or white with blue tinge |
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| | 42. Stem prostrate, rooting at nodes, or ascending |
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| | 43. Leaf blade upper surface dull |
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| | 44. Stems ± ascending or not; leaf not ± erect, < 2 cm, leaf blade upper surface generally puberulent; flower blue; fruit horns slender, near top |
| C. fresnensis |
| | 44' Stems prostrate; leaf ± erect, ± 1 cm, blade upper surface ± glabrous; flower white with blue tinge; fruit horns not slender, on side, or 0 |
| C. roderickii |
| | 43' Leaf blade upper surface generally shiny |
| |
| | 45. Leaf 2–5 cm — leaf margin dentate; flower deep blue to violet; fruit 3.5–4.5 mm, horns minute, ridges 0 |
| C. gloriosus var. gloriosus |
| | 45' Leaf generally < 2.5 cm |
| |
| | 46. Leaf ± as long as wide, margin entire or coarse-toothed |
| |
| | 47. Fruit 4–5 mm, horns minute, not wrinkled, ridges 0; leaf < 1.5 cm; s San Francisco Bay Area, Central Coast (near Hazard Canyon, San Luis Obispo Co.) |
| 2 C. cuneatus var. rigidus |
| | 47' Fruit 7–9 mm, horns wrinkled, not minute, ridges present; leaf generally < 2 cm; s High Sierra Nevada (Kern Plateau) |
| 2 C. pinetorum |
| | 46' Leaf longer than wide, margin generally toothed |
| |
| | 48. Leaf blade < 5 mm wide; twigs puberulent |
| C. pumilus |
| | 48' Leaf blade > 5 mm wide; twigs puberulent or glabrous |
| |
| | 49. Leaf blade lower surface white-woolly, margin turned under; twigs glabrous — Central Coast (San Luis Obispo Co.) |
| C. maritimus |
| | 49' Leaf blade lower surface not white-woolly but hairy on veins, canescent between, margin not turned under; twigs puberulent |
| |
| | 50. Leaf < 2 cm, petiole < 1 mm; fruit generally 5 mm, horns slender, not wrinkled, ridges minute — Outer North Coast Ranges (Sonoma Co.) |
| C. confusus |
| | 50' Leaf < 3.2 cm, petiole < 3 mm; fruit 5–9 mm, horns wrinkled, not slender, ridges prominent |
| C. prostratus |
| | 42' Stem ± prostrate to erect, not rooting at nodes |
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| | 51. Leaf often holly-like, marginal teeth spine-like, at least near tip |
| |
| | 52. Fruit ± 6 mm, horns thick, wrinkled, ridges prominent — flower blue to violet; leaf < 3 cm, generally ± cupped; plant ± ascending, < 6 dm |
| C. jepsonii var. jepsonii |
| | 52' Fruit generally 3–5 mm, horns slender, not wrinkled, ridges 0 or minute |
| |
| | 53. Leaf < 1.5 cm, flat; plant erect — fruit 5 mm; flower blue to lavender |
| C. sonomensis |
| | 53' Leaf 1.5–2.5 cm, flat or not; plant ascending to erect |
| |
| | 54. Plant ascending, weakly arched; leaf blade ± flat, margin not wavy, ± turned under, tip ± truncate |
| C. divergens |
| | 54' Plant ± erect, rigid; leaf blade ± cupped, margin wavy, not turned under, tip obtuse |
| C. purpureus |
| | 51' Leaf generally not holly-like, margin generally dentate, teeth generally not spine-like |
| |
| | 55. Fruit 7–9 mm, horns prominent, wrinkled, ridges present — plant ± prostrate to erect; leaf margins ± turned under or not |
| 2 C. pinetorum |
| | 55' Fruit 3–6 mm, horns slender or minute, not wrinkled, ridges 0 |
| |
| | 56. Leaf margin entire or toothed near tip, blade narrowly oblanceolate to round-obovate |
| |
| | 57. Leaves 2–7 mm, lower surface glabrous; flowers pale blue, sometimes pink — n Peninsular Ranges (Riverside Co.) |
| C. ophiochilus |
| | 57' Leaves 5–50 mm, lower surface minutely canescent to hairy on veins; flowers generally white, sometimes bluish |
| |
| | 58. Branches thick, stiff, straight; blade ± cupped, obovate to round-obovate, margin toothed toward tip; flower light to dark blue — s San Francisco Bay Area, Central Coast (near Hazard Canyon, San Luis Obispo Co.) |
| 2 C. cuneatus var. rigidus |
| | 58' Branches slender, flexible, arched; blade ± flat, narrowly oblanceolate to round-obovate, margin generally entire; flower lavender, pale blue, or white |
| |
| | 59. Leaves closely clustered, blades narrowly oblanceolate |
| C. cuneatus var. fascicularis |
| | 59' Leaves not closely clustered, blades generally round-obovate |
| 2 C. cuneatus var. cuneatus |
| | 56' Leaf margin dentate, blade round to widely elliptic or oblong |
| |
| | 60. Plant generally ± prostrate, < 5 dm — twigs slender; leaf 1–2 cm; San Francisco Bay Area (Point Reyes, Marin Co.) |
| C. gloriosus var. porrectus |
| | 60' Plant generally erect, sometimes ascending, < 2 m |
| |
| | 61. Leaf 15–40 mm; stem flexible, arched; n San Francisco Bay Area, Outer North Coast Ranges |
| C. gloriosus var. exaltatus |
| | 61' Leaf 6–18 mm; stem stiff, straight; San Francisco Bay Area (Bolinas Ridge, sw Marin Co.) |
| C. masonii
|