1	Leaves alternate		(2)
+	Leaves opposite		(3)
2 (1)	Leaf blades widely obovate to suborbiculate, 5–14 mm, apices truncate to retuse; capsules 4–6 mm wide, valves smooth, horns minute or absent.		29 Ceanothus verrucosus
+	Leaf blades elliptic to obovate, 10–25(–33) mm, apices obtuse; capsules 7–12 mm wide, valves rugulose to weakly ridged near apex, horns prominent.		30 Ceanothus megacarpus (in part)
3 (1)	Shrubs matlike to moundlike, 0.1–1 m; stems spreading to weakly ascending (sometimes erect to ascending in C. maritimus and C. sonomensis), sometimes rooting at nodes		(4)
+	Plants not matlike or moundlike, 0.5–6 m; stems usually erect to ascending, sometimes spreading, not rooting at nodes		(18)
4 (3)	Shrubs matlike, 0.1–0.3 m; stems prostrate or spreading		(5)
+	Shrubs moundlike, 0.1–1 m; stems ± prostrate, spreading, or weakly ascending		(8)
5 (4)	Leaf blade margins sharply dentate to spinose-dentate, teeth 3–9		(6)
+	Leaf blade margins entire or denticulate near apex, teeth 0–3		(7)
6 (5)	Leaves not crowded (shorter than internodes); leaf blade adaxial surfaces green, dull; capsules 4–6 mm wide.		42 Ceanothus confusus (in part)
+	Leaves often crowded (usually longer than internodes); leaf blade adaxial surfaces dark green, shiny; capsules 6–9 mm wide.		43 Ceanothus prostratus (in part)
7 (5)	Leaf blade adaxial surfaces dark green, shiny, apices rounded to retuse; capsule horns prominent.		36 Ceanothus fresnensis
+	Leaf blade adaxial surfaces green to grayish green, dull, apices usually truncate, sometimes obtuse; capsule horns minute or weakly developed bulges.		44 Ceanothus pumilus (in part)
8 (4)	Leaf blade margins spinose-dentate		(9)
+	Leaf blade margins entire, denticulate, or serrulate		(11)
9 (8)	Leaf blades widely obovate to suborbiculate, 5–12 mm, apices widely notched, marginal teeth 2–4.		40 Ceanothus sonomensis
+	Leaf blades elliptic, ± oblong, or obovate, 10–20 mm, apices acute or retuse, with an apical tooth, marginal teeth 3–9(–11)		(10)
10 (9)	Shrubs 0.5–1.5 m; stems ascending to erect.		41 Ceanothus divergens (in part)
+	Shrubs 0.1–0.6 m; stems spreading to weakly ascending.		42 Ceanothus confusus (in part)
11 (8)	Leaf blade abaxial surfaces tomentulose.		33 Ceanothus maritimus
+	Leaf blade abaxial surfaces strigillose, sometimes only on or between veins, puberulent, or glabrate		(12)
12 (11)	Leaf blade margins dentate to denticulate or serrulate most of length, teeth 5–31		(13)
+	Leaf blade margins entire, denticulate near apex, or remotely denticulate, teeth 1–5(–7)		(15)
13 (12)	Leaves crowded, blades elliptic to obovate, marginal teeth 5–9.		43 Ceanothus prostratus (in part)
+	Leaves not crowded, blades widely elliptic, obovate, or suborbiculate, marginal teeth 9–31		(14)
14 (13)	Leaf blades 23–31(–45) mm, marginal teeth 13–31; capsule horns minute, intermediate ridges absent; coastal habitats, 30–200 m.		38 Ceanothus gloriosus (in part)
+	Leaf blades 10–20 mm, marginal teeth 9–15; capsule horns prominent, intermediate ridges present; montane habitats, elevations 1600–2600 m.		45 Ceanothus pinetorum (in part)
15 (12)	Leaf blades narrowly oblanceolate to narrowly oblong-lanceolate, margins thick to ± revolute, apex usually truncate, sometimes obtuse.		44 Ceanothus pumilus (in part)
+	Leaf blades elliptic to oblanceolate, margins sometimes thick but not revolute, apex acute, obtuse, retuse, or rounded, or ± truncate		(16)
16 (15)	Leaf blades folded lengthwise; capsule horns absent or weakly developed bulges; axillary short shoots, if present, erect.		37 Ceanothus roderickii
+	Leaf blades flat; capsule horns prominent to minute or absent; axillary short shoots, if present, ascending to spreading		(17)
17 (16)	Leaf blades apices rounded to obtuse, adaxial surfaces pale green; capsule horns subapical, erect.		35 Ceanothus arcuatus
+	Leaf blades apices acute to ± truncate; adaxial surfaces grayish green; capsule horns minute or absent, or lateral, spreading.		48 Ceanothus pauciflorus (in part)
18 (3)	Leaf blade margins spinose-dentate		(19)
+	Leaf blade margins entire, dentate, denticulate, or serrulate		(21)
19 (18)	Stems ± flexible; leaves spreading, abaxial leaf surfaces grayish green.		41 Ceanothus divergens (in part)
+	Stems rigid; leaves spreading to deflexed, abaxial leaf surfaces pale green or pale yellowish green		(20)
20 (19)	Sepals, petals, and stamens 5; leaf blade adaxial surfaces green to dark green; capsule valves smooth, horns slender, intermediate ridges absent; on volcanic soils.		46 Ceanothus purpureus
+	Sepals, petals, and stamens (5–)6(–8); leaf blade adaxial surfaces pale green; capsule valves rugose, horns thick, intermediate ridges present; on serpentine soils.		47 Ceanothus jepsonii
21 (18)	Leaf blade margins entire or remotely denticulate, teeth if present minute, 1–7 (8–19 in C. crassifolius)		(22)
+	Leaf blade margins dentate or denticulate, at least distal to middle, teeth 5–35 (3–5 in C. otayensis)		(27)
22 (21)	Leaves both fascicled and not fascicled on same plant		(23)
+	Leaves not fascicled		(24)
23 (22)	Petioles 1–3 mm; leaf blades elliptic, oblanceolate, obovate, or orbiculate, 6–22(–30) × 3–12(–22) mm; capsules 4–6 mm wide, horns prominent.		32 Ceanothus cuneatus (in part)
+	Petioles 0–1 mm; leaf blades narrowly oblanceolate to narrowly obovate, 3–7 × 1–3 mm; capsules 3–4 mm wide, horns minute or absent.		51 Ceanothus ophiochilus
24 (22)	Branchlets light gray to ashy gray, puberulent to tomentulose, hairs curly or wavy, glabrescent; leaf blade adaxial surfaces grayish green, puberulent, hairs curly or wavy, glabrescent.		48 Ceanothus pauciflorus (in part)
+	Branchlets grayish brown to brown, puberulent or tomentulose, hairs straight, sometimes glabrate; leaf blade adaxial surfaces green, glabrous or sparsely tomentulose, hairs straight, glabrescent		(25)
25 (24)	Leaf blades widely oblanceolate to widely obovate, 5–11 × 4–7 mm; sepals, petals, and nectaries usually lavender, sometimes pale blue; capsules 5–6 mm wide.		32 Ceanothus cuneatus (in part)
+	Leaf blades elliptic to obovate, 10–40 × 5–15(–20) mm; sepals and petals white, nectaries blue or black; capsules 6–12 mm wide		(26)
26 (25)	Leaf blade abaxial surfaces glabrous or strigillose on veins; capsules 7–12 mm wide, horns weakly developed or absent.		30 Ceanothus megacarpus (in part)
+	Leaf blade abaxial surfaces tomentulose; capsules 6–9 mm wide, horns prominent.		31 Ceanothus crassifolius (in part)
27 (21)	Sepals and petals white to cream, nectaries tan to brown, yellow to green, blue, purple, or black		(28)
+	Sepals, petals, and nectaries pale blue, blue, or purple		(31)
28 (27)	Leaf blade margins revolute or thick, abaxial surfaces tomentulose		(29)
+	Leaf blade margins thick or not, not revolute, abaxial surfaces sparsely puberulent (hairs curly) or strigillose, sometimes glabrescent		(30)
29 (28)	Leaf blade margins with 8–19 teeth most of length, apices obtuse to rounded; capsules 5–9 mm wide, horns prominent.		31 Ceanothus crassifolius (in part)
+	Leaf blades margins with 3–5 teeth near apex, apices truncate, retuse, or cuspidate; capsules 4–6 mm wide, horns minute or absent.		50 Ceanothus otayensis
30 (28)	Leaf blade adaxial surfaces dark green; nectaries dark blue to purple; capsules 7–9 mm wide, horns subapical, prominent; serpentine substrates.		34 Ceanothus ferrisiae
+	Leaf blade adaxial surfaces green to yellowish green; nectaries yellow to green; capsules 4–6 mm wide, horns lateral, usually minute, sometimes absent; granitic or metamorphic substrates.		49 Ceanothus perplexans
31 (27)	Leaf blades 4–10 × 4–6 mm, margins denticulate distal to middle, teeth 5–9.		32 Ceanothus cuneatus (in part)
+	Leaf blades 7–40 × 4–22 mm, denticulate most of length, teeth 9–35		(32)
32 (31)	Sepals, petals, and nectaries pale blue to blue; capsule horns prominent, rugose, intermediate ridges present; montane habitats, 1600–2600 m.		45 Ceanothus pinetorum (in part)
+	Sepals, petals, and nectaries deep blue to purple; capsule horns minute, not rugose, intermediate ridges absent; coastal habitats, 30–500 m		(33)
33 (32)	Leaf blades widely elliptic to suborbiculate, 3–40 × 17–22 mm, marginal teeth 13–35.		38 Ceanothus gloriosus (in part)
+	Leaf blades usually elliptic or oval, sometimes suborbiculate, 7–21 × 4–13 mm, marginal teeth 9–17.		39 Ceanothus masonii