1	Stamens 15–25(–27); ovary 10–12-locular; petioles adaxially grooved.		4 Rhododendron maddenii
+	Stamens (8–)10(–14); ovary 5–7-locular.		(2)
2 (1)	Calyx margin not or only rarely hairy, lobes large, 0.8–3 cm; petiole rounded adaxially (concave in R. megacalyx, then with pedicels and calyx whitish pruinose).		(3)
+	Calyx margin hairy, rarely glabrous, small or with obvious lobes; petiole grooved adaxially.		(13)
3 (2)	Pedicels and calyx not scaly, whitish pruinose; calyx lobed to the middle, lobes 2–3 cm; capsule shorter than persistent calyx; midrib and petiole concave adaxially.		5 Rhododendron megacalyx
+	Pedicels and calyx scaly; calyx lobed to the base; capsule longer than persistent calyx; midrib and petiole raised or flat adaxially.		(4)
4 (3)	Leaf blade 11–26 × (3.5–)6–12 cm; corolla 9–13.5 cm.		(5)
+	Leaf blade less than 16 × 6 cm; corolla 3.5–10 cm.		(7)
5 (4)	Leaf blade with veins flat on adaxial surface.		8 Rhododendron excellens
+	Leaf blade with veins strongly impressed on adaxial surface.		(6)
6 (5)	Pedicels and calyx glabrous; capsule 3–3.5 cm; abaxial leaf surface with dense small scales and scattered large scales.		6 Rhododendron nuttallii
+	Pedicels and calyx densely pubescent; capsule 5–7 cm; abaxial leaf surface with more large scales.		7 Rhododendron sinonuttallii
7 (4)	Young shoots sparsely hispid; pedicels and calyx pubescent.		9 Rhododendron dalhousieae
+	Young shoots, pedicels and calyx with scales only.		(8)
8 (7)	Leaf blade 2–5 × (0.5–)1.5–2.5 cm; corolla 3.5–6 cm; petiole 3–5 mm (not recorded for R. mianningense).		(9)
+	Leaf blade 6–16 × (1.5–)2–6 cm; corolla 6–9(–10) cm; petiole 10–30 mm.		(10)
9 (8)	Calyx 15–18 mm; corolla ca. 3.5 cm, pale yellow, outer surface not scaly; abaxial leaf surface with scales overlapping or only slightly apart; petiole glabrous.		10 Rhododendron mianningense
+	Calyx 7–8 mm; corolla 4–6.2 cm, white, outer surface scaly; abaxial leaf surface with scales 1–2 × their diameter apart; petiole hispid.		11 Rhododendron kiangsiense
10 (8)	Stamens 5; corolla lobes denticulate; calyx not scaly outside.		13 Rhododendron chunienii
+	Stamens 10; corolla lobes entire; calyx scaly outside.		(11)
11 (10)	Calyx lobes 15–20 mm, leaflike; pedicel ca. 20 mm; abaxial leaf surface with scales uniform in size.		12 Rhododendron taggianum
+	Calyx lobes 1–10(–14) mm; pedicel 10–15 mm; abaxial leaf surface with scales unequal in size.		(12)
12 (11)	Calyx 1–5 mm; adaxial leaf surface with scales.		14 Rhododendron lindleyi
+	Calyx 8–10(–14) mm; adaxial leaf surface without scales.		15 Rhododendron liliiflorum
13 (2)	Calyx lobes 6–12 mm; young shoots hispid, rarely glabrous; petiole, and usually also leaf blade, hairy.		(14)
+	Calyx lobes obsolete or with lobes 2–6 mm; young shoots, leaf blade or petiole hispid or glabrous.		(21)
14 (13)	Leaf blade without hairs on both surfaces, sometimes hairy on margin; petioles glabrous or hispid; styles glabrous or with a few scales at base.		(15)
+	Leaf blade hispid or villous, at least along central vein; petioles hispid or villous; styles glabrous to densely scaly.		(17)
15 (14)	Leaf margin glabrous; abaxial surface with scales contiguous; corolla scaly outside; calyx margin glabrous.		18 Rhododendron changii
+	Leaf margin hairy, abaxial surface with scales sparse, 3–6 × their diameter apart; corolla not scaly outside; calyx margin densely hairy.		(12)
16	Leaf margin hispid, slightly dentate; calyx lobes ovate-lanceolate; corolla yellow.		16 Rhododendron fletcherianum
+	Leaf margin villous, hairs caducous, entire; calyx lobes oblong; corolla white, or tinged pale red.		17 Rhododendron yungchangense
17 (14)	Young shoots, leaves and pedicels rusty brown-villous; leaf margin glabrous; calyx lobes linear, 6–12 × ca. 2 mm wide.		19 Rhododendron linearilobum
+	Young shoots, leaves and pedicels hispid, or petioles glabrous; leaf margin often densely hispid; calyx lobes ovate, broadly ovate, or oblong-ovate.		(18)
18 (17)	Corolla white or tinged with pale red, not scaly outside.		(19)
+	Corolla pale or fresh yellow, scaly outside.		(20)
19 (18)	Leaf apex obtuse to rounded, sometimes emarginate, pubescent below; scales on abaxial leaf surface slightly more than their own diameter apart (see also 21. R. yizhangense and 22. R. yaogangxianense).		20 Rhododendron levinei
+	Leaf apex acute to acuminate, hispid along central vein below; scales on abaxial leaf surface 2–3 × their diameter apart.		23 Rhododendron ciliatum
20 (18)	Young shoots not hispid; pedicels glabrous; corolla pale yellow, glabrous; leaf margin flat or slightly revolute, villous or glabrous near the base.		24 Rhododendron amandum
+	Young shoots densely brownish hispid; pedicels sometimes strap-shaped-setose; corolla fresh yellow, densely pubescent; leaf margin revolute, densely strap-shaped-setose.		25 Rhododendron valentinianum
21 (13)	Inflorescence 1(–2)-flowered.		(22)
+	Inflorescence 2–5-flowered.		(23)
22 (21)	Young shoots densely brownish scaly; leaf margin densely villous, abaxial surface pale green, scales 1–2 × their own diameter apart.		26 Rhododendron ciliipes
+	Young shoots and leaf margin sparsely hispid, abaxial surface dark brown, scales less than 1 × their own diameter apart.		27 Rhododendron pseudociliipes
23 (21)	Abaxial leaf surface densely scaly; scales unequal, generally less than (rarely 1 ×) their own diameter apart.		(24)
+	Abaxial surface of leaves sparsely scaly; scales unequal, (0.5–)1.5–5 × their own diameter apart.		(28)
24 (23)	Abaxial leaf surface brown when dry; blade rhombic-elliptic or rhombic-lanceolate		28 Rhododendron rhombifolium
+	Abaxial leaf surface grayish green or grayish white when dry; blade elliptic or oblong-elliptic, ovate, obovate or elliptic-lanceolate.		(25)
25 (24)	Corolla 3.5–4.3 cm, yellow, 5-lobed to the middle.		29 Rhododendron leptocladon
+	Corolla 5–7 cm, white tinged with pale red, 5-lobed to upper 1/3.		(26)
26 (25)	Calyx obsolete, margin not ciliate; scales on abaxial leaf surface unequal, to 1 × their own diameter apart.		30 Rhododendron dendricola
+	Calyx undulate, 5-lobed, margin long ciliate hairs; scales on abaxial leaf surface of leaves ± uniform, less then their own diameter apart to almost contiguous.		(27)
27 (26)	Leaf blade ovate, widest below the middle; pedicel 1–2 cm.		31 Rhododendron roseatum
+	Leaf blade elliptic, oblong-elliptic, elliptic-lanceolate or obovate, widest at or above the middle; pedicel 0.5–1 cm.		32 Rhododendron pachypodum
28 (23)	Shoots and petioles densely hispid when young; corolla not scaly, only pubescent outside.		33 Rhododendron ciliicalyx
+	Shoots and petioles glabrous or sometimes sparsely hispid when young; corolla ± scaly outside, sometimes also pubescent.		(29)
29 (28)	Leaf blade oblong-lanceolate or oblong-elliptic; apex acuminate or acute; style longer than corolla.		(30)
+	Leaf blade oblong-obovate, oblong-elliptic or obovate; apex rounded to acute or apiculate; style as long as corolla.		(31)
30 (29)	Pedicel densely pubescent; calyx margin glabrous; corolla 4–5 cm, white, with or without yellow spots inside.		34 Rhododendron taronense
+	Pedicel glabrous; calyx margin sometimes long ciliate; corolla 6–7 cm, white or creamy yellow, with green spots inside.		35 Rhododendron walongense
31 (29)	Leaf blade 3.4–4.5 cm, hispid; pedicel 0.6–0.8 cm; corolla glabrous outside; capsule ca. 0.9 cm.		36 Rhododendron wumingense
+	Leaf blade 4–12 cm, margin glabrous; pedicel 0.8–1.8 cm; corolla pubescent or shortly hairy outside; capsule 1.2–2 cm.		(32)
32 (31)	Leaf blade 7–12 cm; abaxial surface densely or sparsely scaly, adaxial surface sparsely scaly; corolla ca. 7 cm; scales unequal.		30 Rhododendron dendricola
+	Leaf blade 4–8 cm; abaxial surface sparsely scaly, adaxial surface without scales; corolla 4–6 cm; scales nearly uniform in size.		37 Rhododendron scopulorum