Tree to 10 m. Bark dark grey. Branchlets brown and glabrous. Leaves deciduous, 8–10 × 3–4 cm, oblong to elliptic, upper surface glabrous, lower surface villous along the veins, 20–25 secondary veins on each side of the midvein, margins irregularly double-serrate, apex acuminate; petiole glabrous, 0.5–1 cm long. Monoecious; staminate inflorescences catkin-like; pistillate inflorescences catkin-like, terminal, ped unculate, 10–12 cm long, sparsely pubescent. Flowers inconspicuous; bracts densely imbricate, ovate to oblong, 0.7 × 1.3 cm, with three veins, margins slightly serrated. Fruit a nutlet with faint longitudinal ribs. Flowering May to June, fruiting July to October (Taiwan). Rushforth 1986b, Li & Skvortsov 1999. Distribution TAIWAN. Habitat Mixed forest between 1000 and 2000 m asl. USDA Hardiness Zone 8. Conservation status Not evaluated. Illustration NT39, NT208, NT210.
The earliest introduction of this attractive species was apparently that made by Kirkham and Flanagan from their expedition to Taiwan in 1992 (ETOT 122), from a ravine full of choice plants at 1900 m on Taipingshan. Trees from this source are growing at Kew and Wakehurst Place and in private collections. The Kew tree is 3.5–4 m tall and approximately 2–3 m broad. The species was also gathered by the Edinburgh Taiwan Expedition in 1993 (ETE 131), and a plant of this origin is now 3 m tall and growing well at Inverleith. In late October 2006 both these specimens were reported to be in full green leaf, with no sign of change to autumn colour (R. Bayton, J. Latta, pers. comms.); when observed again in December the Kew specimen was only just turning yellow.
The leaves of C. rankanensis are very strongly veined, giving a corrugated effect, and are tinged red when young. With its elongate infructescences it is well worth cultivating (Hudson 2004), but is perhaps not quite in the same rank as C. fangiana. The new shoots are flushed red at their tips.