Hook. Icon. Pl. 1852. t.887.
Verified by:
Erect wiry shrub, to 1.5m, dwarfed at its highest localities. Twigs densely leafy, scaly and sometimes minutely hairy on the youngest growth. Stems with protruding leaf-cushions in the younger parts. Leaves spirally and evenly arranged, very dense and imbricate in the upper part of the twigs and held sub-erect. Blade 4–8 x 0.8–1.6mm, ‘ericoid’, linear or very narrowly elliptic; apex acute (with the extreme point rounded), with an obtuse glandular point; margin entire or somewhat indented with irregular crenulations, somewhat thickened and slightly or not revolute; base tapering, glabrescent above, laxly scaly beneath. Scales disc-shaped, entire with the darker centre thick and slightly impressed. Mid-vein very slightly impressed above, swollen underneath; lateral veins obscure. Petiole 0.6–1 x 0.4–0.6mm, scaly and with a few simple hairs, minutely grooved above and with a swollen, bulbous base. Flower buds to 3.5 x 2.5mm, pink, scaly outside. Bracts all appressed, the outermost subulate, inner ovate, scaly in the upper ½ outside, all with a ciliate margin of white hairs. Inflorescence of solitary flowers or paired, rarely up to 4 in an umbel, hanging vertically. Bracteoles c.3 x 0.5mm, linear-spathulate, long-ciliate upwards, falling early. Pedicels 5–8mm, slender, densely scaly, without hairs. Calyx slightly oblique, scaly outside, glabrous inside, with 5 distinct erect lobes, c.2 x 1–1.3mm, initially appressed to the corolla, later spreading, narrowly sub-ovate-triangular, obtuse. Corolla bright red, tubular, not or slightly oblique and curved, c.15 x 11mm; tube c.11 x 6 x 7mm, densely scaly outside, glabrous inside; lobes c.4 x 5mm, scaly outside except near the margins, broadly ovate to rounded, half-spreading and overlapping to c.halfway, the margins irregularly denticulate. Stamens grouped on the lower side of the flower, slightly exserted to c.1mm; filaments glabrous, c.11mm; anthers brown, c.0.9mm. Disc glabrous. Ovary c.1.8mm, conical, green, densely scaly, gradually tapering distally; style red, to 14mm, glabrous, finally exserted, to c.3mm; stigma club-shaped. Fruit oblong-ovoid, often a little oblique and curved, 7–10 x 3–4mm. Seeds 1.5–2mm, without tails 0.75mm, the longest tail to 0.5mm, the tails often with multiple points.
Malaysia (Borneo), Sabah, Mt Kinabalu, endemic (records from other mountains are all referable to R. borneense).
In primary mossy forest, abundant terrestrially on the open granite dome in exposed sunny places
Argent, G. (2006) Rhododendrons of subgenus Vireya. RHS:London. Page:48