Description

Shrubs to 2 m, often flowering precociously. Young growth lepidote and variably loriform-setose with straight or curved setae. Leaves ± deciduous, flat, mostly ± obovate, more rarely obovate-elliptic, 25-45(-65) x 14-21 (-27) mm, ± rounded at the apex, cuneate at the base, petiole loriform-setose; lower surface variably loriform-setose, usually with at least some setae on the base of the midrib and on margins, the setae straight or slightly curved; scales very unequal, dense, the larger c. 2 x the diameter of the smaller, the smaller usually rapidly becoming greyish, purple or almost black; upper surface puberulent at least along the midrib, rarely lepidote. Inflorescence 2-4-flowered, pedicels (11-) 15-22 mm, variably lepidote, usually loriform-setose, at least towards the base. Calyx usually obscurely lobed, lobes up to 2-5 mm, rarely one lobe considerably longer (up to 7 mm), lepidote, loriform-ciliate or glabrous. Corolla yellow to greenish yellow, sometimes flushed with red, 17-23 mm, tube 8-11 mm, lepidote and glabrous outside. Ovary lepidote, style sometimes puberulent at base. Capsule lepidote, cylindric, 9-11 mm. ** * Rhododendron mekongense * var. * longipilosum * ** Leaves loriform-setose over the whole upper surface ** * Rhododendron mekongense * var. * mekongense * ** Leaves without loriform setae on the upper surface. Loriform setae more widespread, present on at least some of the following: lower leaf surface, pedicels and calyx lobes, as well as on petioles and leaf margins. Calyx loriform-ciliate; pedicels usually loriform-setose over their whole length. ** * Rhododendron mekongense * var. * melinanthum * ** Leaves without loriform setae on the upper surface. Loriform setae more widespread, present on at least some of the following: lower leaf surface, pedicels and calyx lobes, as well as on petioles and leaf margins. Calyx glabrous; pedicels not setose, or setose only at the base. ** * Rhododendron mekongense * var. * rubrolineatum * ** Leaves without loriform setae on the upper surface. Loriform setae very sparse, restricted to petioles and leaf margins and sometimes at the base of the midrib beneath.

Distribution

Altitude

Habitat

Nomenclatural History

Notes

References

Cullen, J. (1980) A Revision of Rhododendron 1: Subgenus Rhododendron sections Rhododendron & Pogonanthum. Notes from the Royal Botanic Garden Edinburgh 39(1):154