Shrubs, evergreen or deciduous. Branchlets thorn-tipped or not. Leaves 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. Inflorescences usually racemelike or paniclelike, sometimes umbellike. Capsules not horned, crested or not; ridges between valves absent.

Distribution

North America, Mexico, Central America (Costa Rica), Central America (Guatemala), Central America (Panama)

Discussion

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).

Selected References

None.

Key

1 Branchlets rigid, thorn-tipped; shrubs evergreen. > 2
2 Leaf blades pinnately veined, adaxial surfaces green, shiny, abaxial surfaces pale green. Ceanothus 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. Ceanothus 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. Ceanothus 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. Ceanothus cordulatus
5 Stems erect, ascending, or spreading, rooting at proximal nodes; leaf blade adaxial surfaces dark green, appressed villosulous or glabrous. Ceanothus 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. Ceanothus microphyllus
9 Sepals, petals, and nectaries blue; petioles 1–3 mm. Ceanothus 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. Ceanothus parvifolius
11 Leaf blades 20–80 mm, adaxial surfaces dull; capsules lobed. Ceanothus 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. Ceanothus 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. Ceanothus 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. Ceanothus 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. Ceanothus foliosus
15 Branchlets pale green to grayish green and glaucous; petiole 2–8 mm; leaf blade margins not wavy. Ceanothus 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. Ceanothus 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. Ceanothus impressus
18 Leaf blades narrowly elliptic, narrowly oblong, or linear, 5–16 × 2–8 mm, adaxial surfaces strigillose, veins not furrowed. Ceanothus 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. Ceanothus 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. Ceanothus 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. Ceanothus 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. Ceanothus 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. Ceanothus 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. Ceanothus parvifolius
24 Leaf blades (10–)20–80 mm, adaxial surfaces dull; capsules lobed. Ceanothus 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. Ceanothus 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. Ceanothus 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. Ceanothus 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. Ceanothus 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). Ceanothus 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. Ceanothus parryi
31 Branchlets angled in cross section, sparsely puberulent or glabrous; leaf blade abaxial surfaces puberulent to villosulous. Ceanothus 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. Ceanothus cyaneus
33 Branchlets not tuberculate; inflorescences 2.5–9 cm, usually racemelike, rarely paniclelike; capsules weakly lobed. Ceanothus 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. Ceanothus 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. Ceanothus oliganthus
36 Leaf blade abaxial surfaces tomentose to tomentulose; petiole 1–4 mm; capsules 3–4 mm wide. Ceanothus 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. Ceanothus foliosus
37 Branchlets pale green to grayish green and glaucous; leaf blades flat, margins not wavy; capsule valves crested. Ceanothus lemmonii

"thin" is not a number.

... more about "Ceanothus subg. Ceanothus"
perigynous +  and epigynous +
Clifford L. Schmidt† +  and Dieter H. Wilken +
Linnaeus +
3-veined +  and veined +
not gland-dotted +
3[-5]-veined +  and pinnate +
spinulose +, spinose +, serrate +  and entire +
denticulate +, dentate +, crenulate +, crenate +  and serrulate +
not +  and thorn-tipped +
not +, crested +  and not horned +
North America +, Mexico +, Central America (Costa Rica) +, Central America (Guatemala) +  and Central America (Panama) +
free +  and adnate +
0 cm0 mm <br />0 m <br /> (0.05 cm0.5 mm <br />5.0e-4 m <br />) +
axillary +  and terminal +
unisexual +  and bisexual +
umbel-like +, paniclelike +  and racemelike +
deciduous +  and persistent +
intrastaminal +
superior +  and inferior +
not fleshy +
perigynous +  and epigynous +
adnate +  and distinct +
6 +  and 5 +
Clawed (?) +, Obovate (?) +  and Spatulate (?) +
2-4-carpellate +
pink +, usually white +  and cream blue or purple +
distinct +
spreading +  and incurved +
6 +  and 5 +
keeled;lanceolate;deltate +
3-veined +  and veined +
Ceanothus subg. Ceanothus +
Ceanothus +
subgenus +
paniclelike +  and racemelike +
gland-tipped +
unarmed +  and armed +
deciduous +  and evergreen +
polygamous +, dioecious +  and synoecious +