State of origin
Rhododendrons and azaleas are plants born from mountainous areas in eastern and South-East Asia, with a huge number coming from Papua New Guinea. The soil of their natural home is rich in rotted, fallen leaves, with heavy summer rainfall quickly draining away, leaving the soil moist but not sodden. While winters are chilly up in the mountains, summer days are rarely blazing hot and, due to the tropical climate, certainly never dry. The altitude also ensures cool summer nights, allowing rhodies to thrive.
Volumes of variety
In nature, the one thousand or so natural species of rhododendron range from ground-hugging sub-shrubs capable of withstanding Himalayan gales and snowstorms, to trees 20–30m tall, with countless small, medium and tall shrubs in between. To these, add the thousands of hybrids specially bred and you’re spoiled for choice. Most are evergreen but there are deciduous forms too, and even rhodies with sweet, spicily fragrant flowers.
Where to buy them
You can buy rhododendrons in areas they most commonly grow. Local nurseries will offer a selection of popular rhododendrons and azaleas.
What to plant them with
Flowering groundcovers that bloom with rhodies add a colourful impact. Hellebores are great choices for part-shade and look terrific when interplanted with creeping blue bugle (Ajuga reptans). Bluebells, a cheap and easily grown bulb with spikes of blue or pink flowers, are another great choice.
No rhododendron (including azaleas) likes to go dry – and they’re not crazy about heat waves either! In Australia, traditional rhodies are at their best in gardens along the Great Dividing Range, in the Dandenongs and Mount Macedon, the Adelaide Hills and Tasmania. Vireya types can be successful in frost-free parts of Melbourne, Sydney and Brisbane, along the subtropical coast and – given frost protection – in coastal Tasmania, in addition to highland tropical areas.
Though there are rhododendrons that do well in full sun, in general they all do better in a spot that’s sunny in the morning and partly shaded in the afternoon. They like the shelter of taller trees and the close company of other shrubs.
Free-draining and deep with plenty of rotted organic matter worked through. Soil that holds moisture but not wetness is ideal.
Summer rain or plenty of water in the hotter months is essential. As the weather becomes cooler towards winter, you can ease off the watering. Lack of summer rain makes rhododendrons difficult to grow in Perth and Adelaide.
If your soil is deep and rich in organic matter, feeding isn’t necessary. Mulching with rotted manure or compost two to three times from October to March will help maintain soil fertility.
You don’t have to prune rhododendrons, but a light shearing after flowering will tidy them up and keep them bushy. Remember, the flower buds form early, so don't prune after February or you'll be cutting off future flowers.