Rhododendron stenophyllum
at the Royal Botanic Garden Edinburgh

Without doubt one of the most distinctive species in the genus, Rhododendron stenophyllum is easily recognized by its narrow, dark green, linear leaves and waxy orange, 3.5cm, campanulate blooms carried in umbels of up to five flowers. In its native habitat, Rhododendron stenophyllum grows as a terrestrial shrub and can attain a height of 3 metres however rarely exceeds 1 metre in cultivation.

Rhododendron stenophyllum - habit
Royal Botanic Garden Edinburgh, Peat House

Originally collected as a dried specimen by Sir Hugh Low in 1867, from which the species was named by J. D. Hooker at Kew (stenophyllum = "narrow leaved" G.), it was not until 1894 that the name Rhododendron stenophyllum was validated when Stapf published his paper on the flora of Mount Kinabalu.

There are now considered to be two distinct subspecies within Rhododendron stenophyllum, distinguished by differing leaf size and occurring at different altitudes (see photos of foliage below for comparison).

Rhododendron stenophyllum ssp. stenophyllum is endemic to Gunung Kinabalu, growing in mossy submontane forest at 2700 - 2800m altitude, and has leaves less than 25x as long as wide, measuring 4 - 7cm long and 0.25 - 0.6cm wide. This subspecies is generally the more floriferous of the two.

Rhododendron stenophyllum ssp. stenophyllum

Rhododendron stenophyllum ssp. angustifolium

Rhododendron stenophyllum ssp. angustifolium, which is the form more often seen in cultivation, is of wider distribution. Whilst also found on Gunung Kinabalu, especially along the main summit trail, at the lower elevation of 1500 - 2400m, it is widely seen elsewhere in Sabah (Trus Madi, G. Alab, G. Lumarku and the Long Pasia region), Brunei (G. Pagon), Kalimantan (Bukit Batu Tiban and G. Kemul) and Sarawak (G. Murud). The leaves in this subspecies are more than 30x as long as wide, measuring up to 12cm long by 0.14 - 0.22cm across.

Rhododendron stenophyllum
Pukeiti, New Zealand

Rhododendron stenophyllum is closely related to Rhododendron nervulosum and Rhododendron exuberans, both of which bear orange flowers and narrow leaves, although these are at least double the width of those of Rhododendron stenophyllum.

Rhododendron nervulosum

Natural hybrids between Rhododendron stenophyllum ssp. angustifolium and a number of other species, such as Rr. crassifolium, maxwellii, durionifolium and fallacinum, occur regularly; all exhibiting the characteristic narrow leaf. The hybrid Rhododendron x liewianum, (R. rugosum x R. stenophyllum), is also found on the main summit trail up Gunung Kinabalu and, whilst the foliage resembles that of Rhododendron nervulosum, the flowers are pink, rather than orange-red, in colour.

Rhododendron durionifolium x Rhododendron stenophyllum

The striking appearance of Rhododendron stenophyllum makes it a popular choice with enthusiasts, so demand at times outpaces supply. This species should present no undue difficulties in cultivation to anyone with some experience of growing vireya species providing the basic cultural requirements are met.

Rhododendron stenophyllum has been used by breeders as both seed and pollen parent to produce a limited range of named hybrids, the progeny again invariably inheriting to some extent the distinctive narrow leaves, with the majority bearing orange flowers.

R.'Raspberry Cordial'
R. stenophyllum x R. christi

R.'Wee Willie Winkie'
R. macgregoriae x R. stenophyllum