Ceanothus thyrsiflorus
Ceanothus subg. Ceanothus
blue blossom, blue blossom ceanothus
thorn-tipped or not.
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.
alternate;
stipules deciduous, thin;
blade usually herbaceous, sometimes leathery, margins entire or teeth gland-tipped, at least when young, stomata on abaxial surface not in crypts; pinnately veined or 3-veined from base.
terminal, usually racemelike, rarely paniclelike, 2.5–9 cm.
usually racemelike or paniclelike, sometimes umbel-like.
sepals, petals, and nectary usually pale to deep blue, rarely white.
3–4 mm wide, weakly lobed;
valves smooth, viscid, not crested.
not horned, crested or not;
ridges between valves absent.
= 24.
Ceanothus thyrsiflorus
Ceanothus subg. Ceanothus
CA; OR; Mexico (Baja California)
North America; Mexico; Central America (Costa Rica, Guatemala, Panama)
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.)
Species of subg. Ceanothus not accounted for here are: Ceanothus buxifolius Willdenow ex Schultes f., C. caeruleus, C. depressus Bentham, and C. ochraceus Suessenguth; all are native to Mexico and Central America.
Species 32 (28 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Branchlets rigid, thorn-tipped; shrubs evergreen. | → 2 |
2. Leaf blades pinnately veined, adaxial surfaces green, shiny, abaxial surfaces pale green. | C. spinosus |
2. Leaf blades 3-veined from base (lateral basal veins sometimes obscure in C. fendleri), adaxial surfaces pale green to dark green or grayish green, dull, abaxial surfaces pale to grayish green. | → 3 |
3. Leaf blades 20–60 × 10–30 mm, abaxial surfaces pale green, appressed-puberulent, glabrescent, adaxial surfaces grayish green, glabrate. | C. incanus |
3. Leaf blades 5–30 × 3–18 mm, abaxial surfaces pale green to grayish green, glabrous, sparsely puberulent, or appressed-villosulous to tomentulose, especially along veins, adaxial surfaces dark to pale green or grayish green, glabrous, glabrate, or appressed-villosulous. | → 4 |
4. Shrubs 1.5–4 m, stems erect; inflorescences usually paniclelike, sometimes racemelike, (3–)5–15 cm. | C. leucodermis |
4. Shrubs 0.5–1.5 m, stems erect, ascending, or spreading; inflorescences umbel-like or racemelike, 1–3.5(–4) cm. | → 5 |
5. Stems ascending to spreading, not rooting at nodes; leaf blade adaxial surfaces pale to grayish green, glabrate. | C. cordulatus |
5. Stems erect, ascending, or spreading, rooting at proximal nodes; leaf blade adaxial surfaces dark green, appressed villosulous or glabrous. | C. fendleri |
1. Branchlets flexible to rigid, not thorn-tipped (sometimes weakly thorn-tipped in C. oliganthus); shrubs deciduous, semideciduous, or evergreen. | → 6 |
6. Leaf blades pinnately veined (proximal pair of secondary veins rarely more prominent and longer than distal pairs). | → 7 |
7. Leaf blade margins usually entire, rarely denticulate distally, adaxial surfaces glabrous or weakly puberulent. | → 8 |
8. Shrubs 0.3–0.8 m; inflorescences usually umbel-like, sometimes racemelike. | → 9 |
9. Sepals, petals, and nectaries white; petioles 0.5–1 mm. | C. microphyllus |
9. Sepals, petals, and nectaries blue; petioles 1–3 mm. | C. foliosus |
8. Shrubs 1–3 m; inflorescences racemelike to paniclelike. | → 10 |
10. Shrubs deciduous; leaf blades flat. | → 11 |
11. Leaf blades 6–25 mm, adaxial surfaces ± shiny; capsules usually not lobed, sometimes weakly lobed. | C. parvifolius |
11. Leaf blades 20–80 mm, adaxial surfaces dull; capsules lobed. | C. integerrimus |
10. Shrubs evergreen or semideciduous; leaf blades ± cupped. | → 12 |
12. Sepals and petals usually white, rarely pale blue; capsules lobed, valves viscid, crested; leaf blade adaxial surfaces dull to ± shiny. | C. palmeri |
12. Sepals and petals pale blue to blue; capsules not lobed, valves not conspicuously viscid, not or weakly crested; leaf blade adaxial surfaces shiny. | C. spinosus |
7. Leaf blade margins serrulate to denticulate (sometimes entire in C. hearstiorum), adaxial surfaces puberulent, pilosulous, villosulous, strigillose, or glandular-papillate, (sometimes glabrous in C. foliosus). | → 13 |
13. Leaf blade margins not revolute. | → 14 |
14. Shrubs 0.2–0.3(–0.5) m; stems spreading; capsules 4–5 mm wide; leaf blade surfaces pilosulous. | C. diversifolius |
14. Shrubs 1–3.5 m; stems erect to ascending; capsules 3–4 mm wide; leaf blade surfaces villosulous to strigillose or glabrate. | → 15 |
15. Branchlets green; petiole 1–3 mm; leaf blade margins usually wavy, sometimes not. | C. foliosus |
15. Branchlets pale green to grayish green and glaucous; petiole 2–8 mm; leaf blade margins not wavy. | C. lemmonii |
13. Leaf blade margins revolute. | → 16 |
16. Branchlets lanate to woolly, glabrescent; leaf blade abaxial surfaces cobwebby, soon glabrescent; inflorescences paniclelike, 5–15 cm. | C. parryi |
16. Branchlets puberulent to tomentulose; leaf blade abaxial surfaces variously hairy, but neither cobwebby nor glabrescent; inflorescences umbel- or racemelike, 1–5(–8) cm. | → 17 |
17. Leaf blade adaxial surfaces strigillose or sparsely puberulent, not glandular papillate. | → 18 |
18. Leaf blades oblong, elliptic, or suborbiculate, 6–25 × 4–15 mm, adaxial surfaces sparsely puberulent, veins furrowed. | C. impressus |
18. Leaf blades narrowly elliptic, narrowly oblong, or linear, 5–16 × 2–8 mm, adaxial surfaces strigillose, veins not furrowed. | C. dentatus |
17. Leaf blade adaxial surfaces glandular-papillate, sometimes also puberulent or villosulous. | → 19 |
19. Shrubs 1–5 m; stems erect to ascending; leaf blades 12–50 × 6–15 mm; capsules 2–3 mm wide. | C. papillosus |
19. Shrubs 0.1–0.3 m; stems prostrate to spreading, some flowering branches ascending; leaf blades 8–20 × 2–10 mm; capsules 4–5 mm wide. | C. hearstiorum |
6. Leaf blades 3-veined from base (proximal pair of secondary veins longer than those above, sometimes equaling central vein). | → 20 |
20. Leaf blade margins usually entire, rarely denticulate or serrulate distally. | → 21 |
21. Petioles 0.5–1 mm; leaves often fascicled, blades 2–10 × 1–6 mm; se United States. | C. microphyllus |
21. Petioles (1–)1.5–12 mm; leaves not fascicled, blades 6–80 × 3–45 mm; w United States. | → 22 |
22. Branchlets light gray; capsules prominently rugose. | C. incanus |
22. Branchlets pale green or green to grayish green or brown; capsules smooth to ± rugulose. | → 23 |
23. Shrubs 0.5–1 m; leaf blades widely elliptic to suborbiculate; inflorescences umbel-like to racemelike, 1.5–4 cm; sepals and petals white; nectary yellow to yellow-green. | C. martini |
23. Shrubs 1–4 m; leaf blades elliptic, oblong-elliptic, lanceolate, or ovate; inflorescences racemelike to paniclelike, 3–25 cm; sepals and petals white or blue; nectary usually white or blue, rarely pink. | → 24 |
24. Leaf blades 6–25 mm, adaxial surfaces ± shiny; capsules usually not lobed, sometimes weakly lobed. | C. parvifolius |
24. Leaf blades (10–)20–80 mm, adaxial surfaces dull; capsules lobed. | C. integerrimus |
20. Leaf blade margins serrate, serrulate, or denticulate (rarely entire in C. cyaneus). | → 25 |
25. Leaf blades (20–)25–100(–130) × 10–64 mm, margins serrate to serrulate, teeth (35–)40–150+; sepals and petals white to cream (sometimes pink-tinged in C. sanguineus, blue in C. arboreus). | → 26 |
26. Leaf blades leathery, resinous, aromatic, adaxial surfaces shiny. | C. velutinus |
26. Leaf blades herbaceous, not resinous, not aromatic, adaxial surfaces dull. | → 27 |
27. Leaf blades usually elliptic to lanceolate, sometimes ovate or oblanceolate; inflorescences terminal, globose to hemispheric. | C. herbaceus |
27. Leaf blades ovate, oblong-ovate, or widely elliptic; inflorescences terminal or axillary, cylindric to conic. | → 28 |
28. Shrubs evergreen; branchlets brown, tomentulose; sepals, petals, and nectaries blue; California Channel Islands. | C. arboreus |
28. Shrubs deciduous; branchlets green to reddish brown, puberulent, glabrescent; sepals, petals, and nectaries usually white to cream, sometimes pink-tinged; mainland United States. | → 29 |
29. Leaf blade apices usually acuminate to acute, rarely obtuse; capsules not lobed, valves ± rugulose, crested; e North America. | C. americanus |
29. Leaf blade apices acute to rounded; capsules weakly lobed near apex, valves smooth, not or sometimes weakly crested; w North America (disjunct in Michigan). | C. sanguineus |
25. Leaf blades 5–50 × 3–30 mm, margins usually denticulate, sometimes serrulate (rarely entire in C. cyaneus), teeth 19–71; sepals and petals blue (white in C. martini, rarely white in C. oliganthus and C. thyrsiflorus). | → 30 |
30. Leaf blade margins revolute. | → 31 |
31. Branchlets usually round, sometimes ± angled, in cross section, lanate to woolly, glabrescent; leaf blade abaxial surfaces cobwebby, soon glabrescent. | C. parryi |
31. Branchlets angled in cross section, sparsely puberulent or glabrous; leaf blade abaxial surfaces puberulent to villosulous. | C. griseus |
30. Leaf margins not revolute (sometimes incompletely revolute in C. thyrsiflorus). | → 32 |
32. Branchlets angled in cross section. | → 33 |
33. Branchlets often tuberculate (tubercles minute, brownish); inflorescences 15–30(–40) cm, paniclelike; capsules deeply lobed. | C. cyaneus |
33. Branchlets not tuberculate; inflorescences 2.5–9 cm, usually racemelike, rarely paniclelike; capsules weakly lobed. | C. thyrsiflorus |
32. Branchlets round in cross section (rarely angled in cross section in C. oliganthus). | → 34 |
34. Sepals and petals white, nectaries pale yellow to yellow-green; leaf blade margins serrulate distal to middle. | C. martini |
34. Sepals and petals pale blue to blue, nectaries usually pale to dark blue or purplish blue, rarely white; leaf blade margins denticulate or serrulate most of length. | → 35 |
35. Branchlets reddish brown to brown; leaf blades ovate to widely elliptic. | → 36 |
36. Leaf blade abaxial surfaces glabrate to hirtellous; petiole 3–8 mm; capsules 4–7 mm wide. | C. oliganthus |
36. Leaf blade abaxial surfaces tomentose to tomentulose; petiole 1–4 mm; capsules 3–4 mm wide. | C. tomentosus |
35. Branchlets green, pale green, or grayish green; leaf blades narrowly elliptic, oblong-elliptic, or oblanceolate. | → 37 |
37. Branchlets green; leaf blades ± folded lengthwise, margins usually ± wavy, sometimes not; capsule valves not or weakly crested. | C. foliosus |
37. Branchlets pale green to grayish green and glaucous; leaf blades flat, margins not wavy; capsule valves crested. | C. lemmonii |
CA
OR
Flora NW
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
