There are some 1,000 species of rhododendrons. While they grow all around the world, the largest variety of species is found in China and the Himalayas. Thanks to the passionate botanists who travelled to these far-off lands in the 19th and 20th centuries, our gardens today are resplendent with the spring blooms of rhododendrons. This leaflet contains some practical tips for growing them.
Rhododendrons and azaleas
Rhododendrons and azaleas are members of the heath family (Ericaceae). The name rhododendron comes from the Greek words rhodon for rose, and dendron, tree. Literally, then, rhododendrons are “trees with rose-coloured flowers.”
Until the 19th century, botanists distinguished between the Azalea and the Rhododendron genera. Today, only the Rhododendron genus is recognized, although we still talk about azaleas. Many gardeners still consider rhododendrons and azaleas members of two separate groups, distinguishing them according to the following features.
- Large flowers with 10 stamens
- Large, sturdy evergreen leaves
- Shrubs up to several metres in height
- Small flowers with 5 stamens
- Small, delicate deciduous leaves
- Small shrubs
Rhododendrons are bushy shrubs, and the different species may be upright, prostrate or open in habit. Depending on their geographic origin, they range in height from a few centimetres for high-altitude and northern species to over 10 metres for some tropical species.
Rhododendrons put on a fabulous spring show in May and June, blooming in a range of colours from white to mauve and every shade of pink. Yellow and orange flowers are more common on azaleas.
Most rhododendrons have no fragrance, although there are some exceptions. A single Rhododendron luteum bush, for instance, will fill a garden with its scent in spring.
Most rhododendrons have evergreen leaves. Only deciduous azaleas and a few species of alpine and arctic rhododendrons lose their leaves in winter.
The large or small, round or lance-shaped leaves give these shrubs an attractive shiny appearance year-round. Deciduous azaleas also turn a lovely golden or bronze hue in autumn.