Rhododendron subsect. Boothia in Flora of China @ efloras.org

14. Rhododendron subsect. Boothia (Hutchinson) Sleumer, Bot. Jahrb. Syst. 74: 530. 1949.

黄花杜鹃亚组 huang hua du juan ya zu

Yang Hanbi (杨汉碧 Yang Han-pi); David F. Chamberlain

Rhododendron ser. Boothia Hutchinson in J. B. Stevenson, Sp. Rhodod. 155. 1930 ["Boothii"].

Shrubs, (0.05–)0.3–2.5(–3) m tall, often epiphytic; young shoots scaly, mostly setose, sometimes otherwise glabrous. Leaves large; leaf blade leathery; abaxial surface whitish papillose or glaucous, scales 0.5–2 × their own diameter apart or sometimes contiguous, saucer-shaped or vesicular, deeply sunk in pits, golden yellow to brown or dark brown; adaxial surface glabrous or scaly, sometimes setose on midrib and veins. Inflorescence terminal, 1–11-flowered; pedicels scaly, usually setose; calyx (1–)2–15 mm, usually 5-lobed, sometimes reduced to undulate rim, scaly, margin mostly ciliate or setose; corolla broadly campanulate or rotate to saucer-shaped, usually yellow, rarely greenish, white or reddish, sometimes spotted, outer surface scaly, sometimes sparsely pubescent; stamens 10; ovary 5(or 6)-celled; style short, thick, sharply bent, usually scaly at base. Capsule ovoid to cylindric-ovoid, 8–17 mm, scaly. Seed prominently winged and finned.

Seven species: Bhutan, China, India, Myanmar, Sikkim; seven species (two endemic) in China.

1 Inflorescence 1–2(–3)-flowered; scales on abaxial leaf surface vesicular, with narrow rim. (2)

+ Inflorescence usually 3–11-flowered; scales on abaxial leaf surface usually saucer-shaped, with broad rim. (3)

2 (1) Corolla yellow, broadly campanulate; adaxial leaf surface with only a few setae at base of midrib. 137 Rhododendron megeratum

+ Corolla white, sometimes tinged pink, rotate; adaxial leaf surface setose. 138 Rhododendron leucaspis

3 (1) Pedicels 20–50 mm, thin, flexuous; corolla 0.9–1.4 cm; calyx lobes usually reflexed. 139 Rhododendron leptocarpum

+ Pedicels up to 20 mm, stout, rigid; corolla 1.5–3(–4) cm; calyx lobes usually not reflexed. (4)

4 (3) Calyx saucerlike, lobes reduced to an undulate rim, 1–2 mm. 140 Rhododendron chrysodoron

+ Calyx lobes rounded, ovate to oblong, 3–15 mm. (5)

5 (4) Pedicels setose; calyx lobes (7–)10–15 mm; leaf apex acuminate; midrib and lateral veins adaxially setose. 141 Rhododendron boothii

+ Pedicels not setose; calyx lobes 3–8 mm; leaf apex rounded or obtuse; midrib and main veins adaxially glabrous. (6)

6 (5) Inflorescence 4–8-flowered; calyx 3–6 mm; corolla 13–20 mm; scales on abaxial leaf surface usually uniform, small, 0.5–1 × their own diameter apart. 142 Rhododendron sulfureum

+ Inflorescence 2–3-flowered; calyx 6–8 mm; corolla 20–26 mm; scales on abaxial leaf surface dimorphic, larger, contiguous. 143 Rhododendron dekatanum

Lower Taxa