1	Branchlets rigid, thorn-tipped; shrubs evergreen		(2)
+	Branchlets flexible to rigid, not thorn-tipped (sometimes weakly thorn-tipped in C. oliganthus); shrubs deciduous, semideciduous, or evergreen		(6)
2 (1)	Leaf blades pinnately veined, adaxial surfaces green, shiny, abaxial surfaces pale green.		10 Ceanothus spinosus (in part)
+	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 (2)	Leaf blades 20–60 × 10–30 mm, abaxial surfaces pale green, appressed-puberulent, glabrescent, adaxial surfaces grayish green, glabrate.		12 Ceanothus incanus (in part)
+	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 (3)	Shrubs 1.5–4 m, stems erect; inflorescences usually paniclelike, sometimes racemelike, (3–)5–15 cm.		11 Ceanothus leucodermis
+	Shrubs 0.5–1.5 m, stems erect, ascending, or spreading; inflorescences umbel-like or racemelike, 1–3.5(–4) cm		(5)
5 (4)	Stems ascending to spreading, not rooting at nodes; leaf blade adaxial surfaces pale to grayish green, glabrate.		13 Ceanothus cordulatus
+	Stems erect, ascending, or spreading, rooting at proximal nodes; leaf blade adaxial surfaces dark green, appressed villosulous or glabrous.		14 Ceanothus fendleri
6 (1)	Leaf blades pinnately veined (proximal pair of secondary veins rarely more prominent and longer than distal pairs)		(7)
+	Leaf blades 3-veined from base (proximal pair of secondary veins longer than those above, sometimes equaling central vein)		(20)
7 (6)	Leaf blade margins usually entire, rarely denticulate distally, adaxial surfaces glabrous or weakly puberulent		(8)
+	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)
8 (7)	Shrubs 0.3–0.8 m; inflorescences usually umbel-like, sometimes racemelike		(9)
+	Shrubs 1–3 m; inflorescences racemelike to paniclelike		(10)
9 (8)	Sepals, petals, and nectaries white; petioles 0.5–1 mm.		4 Ceanothus microphyllus (in part)
+	Sepals, petals, and nectaries blue; petioles 1–3 mm.		26 Ceanothus foliosus (in part)
10 (8)	Shrubs deciduous; leaf blades flat		(11)
+	Shrubs evergreen or semideciduous; leaf blades ± cupped		(12)
11 (10)	Leaf blades 6–25 mm, adaxial surfaces ± shiny; capsules usually not lobed, sometimes weakly lobed.		7 Ceanothus parvifolius (in part)
+	Leaf blades 20–80 mm, adaxial surfaces dull; capsules lobed.		8 Ceanothus integerrimus (in part)
12 (10)	Sepals and petals usually white, rarely pale blue; capsules lobed, valves viscid, crested; leaf blade adaxial surfaces dull to ± shiny.		9 Ceanothus palmeri
+	Sepals and petals pale blue to blue; capsules not lobed, valves not conspicuously viscid, not or weakly crested; leaf blade adaxial surfaces shiny.		10 Ceanothus spinosus (in part)
13 (7)	Leaf blade margins not revolute		(14)
+	Leaf blade margins revolute		(16)
14 (13)	Shrubs 0.2–0.3(–0.5) m; stems spreading; capsules 4–5 mm wide; leaf blade surfaces pilosulous.		28 Ceanothus diversifolius
+	Shrubs 1–3.5 m; stems erect to ascending; capsules 3–4 mm wide; leaf blade surfaces villosulous to strigillose or glabrate		(15)
15 (14)	Branchlets green; petiole 1–3 mm; leaf blade margins usually wavy, sometimes not.		26 Ceanothus foliosus (in part)
+	Branchlets pale green to grayish green and glaucous; petiole 2–8 mm; leaf blade margins not wavy.		27 Ceanothus lemmonii (in part)
16 (13)	Branchlets lanate to woolly, glabrescent; leaf blade abaxial surfaces cobwebby, soon glabrescent; inflorescences paniclelike, 5–15 cm.		19 Ceanothus parryi (in part)
+	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 (16)	Leaf blade adaxial surfaces strigillose or sparsely puberulent, not glandular papillate		(18)
+	Leaf blade adaxial surfaces glandular-papillate, sometimes also puberulent or villosulous		(19)
18 (17)	Leaf blades oblong, elliptic, or suborbiculate, 6–25 × 4–15 mm, adaxial surfaces sparsely puberulent, veins furrowed.		22 Ceanothus impressus
+	Leaf blades narrowly elliptic, narrowly oblong, or linear, 5–16 × 2–8 mm, adaxial surfaces strigillose, veins not furrowed.		23 Ceanothus dentatus
19 (17)	Shrubs 1–5 m; stems erect to ascending; leaf blades 12–50 × 6–15 mm; capsules 2–3 mm wide.		24 Ceanothus papillosus
+	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.		25 Ceanothus hearstiorum
20 (6)	Leaf blade margins usually entire, rarely denticulate or serrulate distally		(21)
+	Leaf blade margins serrate, serrulate, or denticulate (rarely entire in C. cyaneus)		(25)
21 (20)	Petioles 0.5–1 mm; leaves often fascicled, blades 2–10 × 1–6 mm; se United States.		4 Ceanothus microphyllus (in part)
+	Petioles (1–)1.5–12 mm; leaves not fascicled, blades 6–80 × 3–45 mm; w United States		(22)
22 (21)	Branchlets light gray; capsules prominently rugose.		12 Ceanothus incanus (in part)
+	Branchlets pale green or green to grayish green or brown; capsules smooth to ± rugulose		(23)
23 (22)	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.		6 Ceanothus martini (in part)
+	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 (23)	Leaf blades 6–25 mm, adaxial surfaces ± shiny; capsules usually not lobed, sometimes weakly lobed.		7 Ceanothus parvifolius (in part)
+	Leaf blades (10–)20–80 mm, adaxial surfaces dull; capsules lobed.		8 Ceanothus integerrimus (in part)
25 (20)	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)
+	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)
26 (25)	Leaf blades leathery, resinous, aromatic, adaxial surfaces shiny.		5 Ceanothus velutinus
+	Leaf blades herbaceous, not resinous, not aromatic, adaxial surfaces dull		(27)
27 (26)	Leaf blades usually elliptic to lanceolate, sometimes ovate or oblanceolate; inflorescences terminal, globose to hemispheric.		2 Ceanothus herbaceus
+	Leaf blades ovate, oblong-ovate, or widely elliptic; inflorescences terminal or axillary, cylindric to conic		(28)
28 (27)	Shrubs evergreen; branchlets brown, tomentulose; sepals, petals, and nectaries blue; California Channel Islands.		15 Ceanothus arboreus
+	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 (28)	Leaf blade apices usually acuminate to acute, rarely obtuse; capsules not lobed, valves ± rugulose, crested; e North America.		1 Ceanothus americanus
+	Leaf blade apices acute to rounded; capsules weakly lobed near apex, valves smooth, not or sometimes weakly crested; w North America (disjunct in Michigan).		3 Ceanothus sanguineus
30 (25)	Leaf blade margins revolute		(31)
+	Leaf margins not revolute (sometimes incompletely revolute in C. thyrsiflorus)		(32)
31 (30)	Branchlets usually round, sometimes ± angled, in cross section, lanate to woolly, glabrescent; leaf blade abaxial surfaces cobwebby, soon glabrescent.		19 Ceanothus parryi (in part)
+	Branchlets angled in cross section, sparsely puberulent or glabrous; leaf blade abaxial surfaces puberulent to villosulous.		21 Ceanothus griseus
32 (30)	Branchlets angled in cross section		(33)
+	Branchlets round in cross section (rarely angled in cross section in C. oliganthus)		(34)
33 (32)	Branchlets often tuberculate (tubercles minute, brownish); inflorescences 15–30(–40) cm, paniclelike; capsules deeply lobed.		18 Ceanothus cyaneus
+	Branchlets not tuberculate; inflorescences 2.5–9 cm, usually racemelike, rarely paniclelike; capsules weakly lobed.		20 Ceanothus thyrsiflorus
34 (32)	Sepals and petals white, nectaries pale yellow to yellow-green; leaf blade margins serrulate distal to middle.		6 Ceanothus martini (in part)
+	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 (34)	Branchlets reddish brown to brown; leaf blades ovate to widely elliptic		(36)
+	Branchlets green, pale green, or grayish green; leaf blades narrowly elliptic, oblong-elliptic, or oblanceolate		(37)
36 (35)	Leaf blade abaxial surfaces glabrate to hirtellous; petiole 3–8 mm; capsules 4–7 mm wide.		16 Ceanothus oliganthus
+	Leaf blade abaxial surfaces tomentose to tomentulose; petiole 1–4 mm; capsules 3–4 mm wide.		17 Ceanothus tomentosus
37 (35)	Branchlets green; leaf blades ± folded lengthwise, margins usually ± wavy, sometimes not; capsule valves not or weakly crested.		26 Ceanothus foliosus (in part)
+	Branchlets pale green to grayish green and glaucous; leaf blades flat, margins not wavy; capsule valves crested.		27 Ceanothus lemmonii (in part)