QBARS - v28n4 Rhododendron intranervatum

Rhododendron intranervatum
J. Rouse, Victoria, Australia

In November 1973, one of my plants of R. intranervatum flowered in the glasshouse for the first time when about 30 cm. (1 foot) tall. It was grown from seed obtained from Great Britain in 1969 by Tom Lelliott. In Borneo, R intranervatum grows epiphytically, but this plant, shown in the photograph, is growing in a mixture of pelleted styrene foam and peat moss, 75:25 percent by volume, together with the usual nutrients.
This most striking rhododendron differs from others in the Vireya series through the leaves which are 15-20 cm. long, 5-10 cm. wide and with prominent ridges perpendicular to the midrib. They occur either opposite in pairs or singly and with an inter-node of 2-6 cm. The corollas are five-lobed, funnel-shaped opening to 3-4 cm. in diameter and a light yellow in color. To date, the flowers have come in threes or fours.
R. intranervatum propagates readily from seed or cuttings and I expect it to be easily grafted onto hybrid Vireya stock. I prefer to grow Vireya Rhododendron in the garden or in a shade house and mostly they grow well outside since in winter the temperature seldom drops below more than 2° - 3°C of frost, and in summer although the temperature may climb to 40° - 42°C (about 108° F.), adequate shade or automatic occasional misting above 30°C (85° F.) is easily provided. However, the more epiphytic plants such as R. jasminiflorum or R. arfakianum grow more readily in the ground when grafted and I expect this will apply to R. intranervatum .
Comparing the flowers of R. intranervatum with other yellow flowering Vireya Rhododendrons, there is no doubt in my mind that the flowers of R. laetum and R. aurigeranum are a purer or more beautiful yellow and usually they have more flowers in the truss. However, both these rhododendrons suffer from long internodes of 10-20 cm. making the plants tall and straggly. I have crossed R. intranervatum with both these rhododendrons and hope to obtain among the hybrids, plants with shorter internodes than R. laetum or R. aurigeranum but with their glorious golden yellow flowers.