Rhododendrons have two key features that make them top additions to coldclimate gardens: they are evergreen and have spectacular spring flowers.
Despite these pluses, they’re not really considered on-trend. However, that may be changing, as I saw them recently in medalwinning gardens at the Chelsea Flower Show in the UK, which may suggest they are gaining in the floral fashion stakes.
There was a time when rhododendrons were the height of garden fashion in coldclimate gardens. In Victorian and Edwardian times, the passion for them was due in part to their combination of spectacular flowers and evergreen leaves, but also due to the craze for anything from the “Far East”.
Most spring-flowering evergreen rhododendrons bud up in late summer and autumn, then sit tight through winter waiting for spring sunshine before their flowers open.
The old rhododendrons in my garden are in bud but are not going to crack a flower until all the other spring flowers have bloomed. Just when I’m convinced they won’t flower, they burst into clouds of pink and mauve.
There are earlier-flowering cultivars including the early red rhodies that have been in flower for some weeks but peak displays are still on the way. There are about 800 rhododendron species, from the commonly grown evergreen azaleas to the tree-sized Rhododendron arboreum.
While most species come from habitats in the northern hemisphere such as Europe, Asia, the Himalayas and Myanmar, and across North America, there are species in our hemisphere at high altitudes in the tropics.
The red-flowered Australian rhododendron ( R. lochiae) is included in a group known as vireya or tropical rhododendrons. These are gaining a strong following and are well worth growing in Tassie.
IN THE GARDEN
Evergreen rhododendrons come in a spectrum of colours. As well as reds, pinks, lilacs, whites and yellows, there are the more unusual blue forms (such as Blue Diamond).
Some flowers are speckled while others are bi-colour. Some are also scented. There are also varieties with variegated leaves including the red and white-flowered President Roosevelt, one of the easiest of all to grow.
Their traditional landscape use is as evergreen shrubberies or as an evergreen understorey beneath tall deciduous trees, often surrounded with a carpet of spring bulbs such as bluebells. Rhododendrons also make excellent companions for Australian native plants, growing well in the filtered shade of eucalypts
In small gardens, compact varieties can be grown under small deciduous trees such as Japanese maples. Smaller rhododendrons can also be grown in large containers.
PLANTING AND CARE
These are long-lived plants and expensive to buy so give them the best care.
Rhododendrons are not top sellers so plants in garden centres may have been in their pots for several seasons and could be root-bound. Avoid spindly, woody or rootbound specimens, instead choosing robust plants with strong growth, healthy foliage and a vigorous root system.
Despite their exotic appearance, rhododendrons are low-maintenance plants. The main task is to deadhead spent flowers. Strong new shoots (often called “candles”) follow flowering so deadhead immediately after, before the new shoots begin to elongate. Deadheading removes unwanted seed heads and tidies the plant.
A cluster of Pink Pearl rhododendrons in bloom bring colour to the garden. Picture: ADOBE STOCK