There are many species of rhododendrons, most of which are capable of thriving in the cooler parts of Australia. However, that doesn't mean they grow under any condition. Rhododendrons have quite specific needs that gardeners need to fill in order to persuade these distinctive plants to flower. You'll need to consider the following factors before you begin planting.
Where to Plant Rhododendrons
Rhododendrons are very sensitive to heat and sunlight. They prefer to be planted in cool, shady parts of the garden. The ideal site gets sun during the morning but is shaded from the hot afternoon rays. Some species of rhododendrons can reach up to five metres in height, so gardeners should consider whether there will be enough space for the mature plant when choosing a growing site.
The Importance of Soil Type for Growing Rhododendrons
Rhododendrons need very rich, deep soil. Gardeners who have nutrient-poor soil need to add plenty of organic materials to fuel the growth of these plants. The soil should ideally be moist, but not saturated; it's important that the soil drains well to avoid root rot. Some gardeners like to grow dwarf rhododendrons in pots, in which case they need to add pebbles to the bottom of the containers underneath the potting soil, to ensure good drainage. Finally, rhododendrons prefer acidic soil, so gardeners should avoid adding lime, which makes soil more alkaline. Gardeners who are working with naturally alkaline soil can add an acidifying fertiliser, such as ammonium nitrate or ammonium sulphate, to make the conditions more suitable.
How to Water Rhododendrons
The root ball of a rhododendron should never be allowed to dry out. During periods of dry, hot weather, this means watering regularly with just enough water to make the soil moist, but not saturated. Gardeners should look out for wilting leaves on their rhododendrons, which is a clear sign that the plant needs water. Adding mulch around the plant can also help to keep the roots moist, particularly during hot weather.
How to Fertilise Rhododendrons
Rhododendrons grow fastest and produce their flowers during spring, which is when they most desperately need nutrients. Gardeners should add fertiliser at this time of year. Many retailers sell fertilisers that are specifically formulated for rhododendrons and azaleas, which provide exactly the right balance of nutrients. Yellow leaves are a sure sign that rhododendrons need fertiliser.
How to Prune Rhododendrons
It is easy to remove dead flowers from rhododendrons; gardeners simply need to grip the flower spike and twist it sharply. Pruning is best carried out in winter and can encourage strong new growth during the next season. Gardeners can prune the plant right back to the wood, using secateurs or even a hacksaw, without harming it. However, most rhododendrons continue to flower each season with minimal pruning.