The Rhododendron series of stamps features the rare species of flowering plants that are found on the slopes of Mount Kinabalu, Sabah. There are 35 species of Rhododendrons found in Sabah and 25 of these species can be seen on the slopes of Mount Kinabalu. Some 12 species of Rhododendrons are unique to Sabah.
Rhododendrons belong to the Ericacae family and are characterized by their large leaves and large terminal flower clusters. The flowers are shaped like bells, with colours ranging from white, pink, purple to red. However, the flowers cannot withstand direct and intense sunlight which would bleach the colour of the flowers. Rhododendrons need sandy soil with partial shade to grow well.
Some Rhododendrons grow as shrubs while others grow as trees up to four metres in height. These flowering plants are popularly used as borders or decorative items as part of the landscape, and also as specimen plants.
The Rhododendron nervulosum has long, narrow and flat leaves with scales. It also has an abundant of small veins. The species grows as shrubs with smooth branches, end with one or two flowering umbels. It is usually found at altitudes between 2,500 metres and 3,000 metres.
Rhododendron stenophyllum has very narrow, dark green leaves with sparse scales. Its flowers range from orange to red and are waxy in appearance.
It grows at altitudes from 2,700 metres to 2,800 metres and has two different subspecies that cultivates at different altitudes. The species can only be found in Mount Kinabalu and it flowers throughout the year, especially from February to June.
Rhododendron rugosum is easily distinguished by its pink, hairy flowers and coarsely veined, wrinkled leaves with brown scales. It grows in the altitudinal range of 2,000 to 3,500 metres.
The species cultivates well but rarely flowers. It grows in shrubs or small trees up to 8 metres. The twigs are covered by dense brown scales that rub off easily.
This species is highly distinctive with its covering of white hair. It produces flowers throughout the year, but the main flowering season is March and April.
Rhododendron stapfianum grows in shrubs up to 1 metre in height. The twigs are rounded and green in colour with white hair and brown scales.
This species has the largest individual flowers of any Bornean Rhododendron. The flowers are rich gold or apricot in colour. The enormous broad green leaves distinguished this species, and it grows in partially shaded moist soil at altitudes between 2,700 and 3,650 metres. At the upper end of the altitude, the size of the plants are much smaller.
This species does not thrive as potted plants and does not produce any flower in cultivation.