黄钟杜鹃 huang zhong du juan

Rhododendron flinckii Davidian; R. lanatum var. luciferum Cowan; R. luciferum (Cowan) Cowan.

Shrubs or small trees, 1–3 m tall; young shoots and petioles densely whitish to tawny woolly-tomentose. Petiole 10–15 mm; leaf blade leathery, elliptic to obovate or oblong-obovate, 6–11 × 2.5–4.5 cm; base obtuse or broadly cuneate; margin revolute; apex obtuse or subrounded, apiculate; abaxial surface white, densely pale chocolate brown to rufous woolly, hairs ± crispate dendroid; adaxial surface glabrous except for groove of midrib, midrib and lateral veins prominent abaxially. Inflorescence racemose-umbellate, 5- or 10-flowered; rachis 3–10 mm, woolly-tomentose. Pedicel 1.5–2 cm, densely whitish to tawny woolly-tomentose; calyx 1–2 mm, tomentose or glabrescent; corolla broadly campanulate, sulfur-yellow, with red spots, 3.5–4.5 cm; lobes 5, rounded, emarginate; stamens 10, unequal, 1.5–2.6 cm, filaments pubescent at base; ovary 5-lobed, ca. 6 mm, densely tawny-tomentose; style ca. 2.6 cm, glabrous; stigma lobulate. Capsule elongate-cylindric, slightly curved, 15–25 × 4–8 mm, ± tomentose. Fl. May, fr. Aug.

Coniferous forests, Rhododendron thickets, mountain slopes; 3100–4400 m. SE Xizang [Bhutan, Sikkim].

Rhododendron luciferum may be a distinct species, differing in the shape of the leaves and their loose, very thick, rufous indumentum. Moreover, the taxon has a more easterly distribution. The largely Bhutanese R. flinckii may also be a distinct species, differing in the red, more velutinous leaf indumentum.

However, Hans Eiberg (August 2010) noted that the indumentum of Rhododendron luciferum is not rufous. According to Eiberg, "this species does not have a very thick woolen (rufous) red-brown indumentum, but a compact(felted)green-brown indumentum...The indumentum can be rolled off the leaf in big parts (when it is wet) and formed into a wick (best method to identify the species). No glands are found on the leaf and ovary (not a Taliensa)."