A Guide to Growing & Caring for Rhododendrons
The rhododendron is a common woodland shrub that you may notice while out and about, without even realising it!
Part of the evergreen & deciduous shrubs group, this plant can grow over 6m tall depending on if it is a dwarf, semi-dwarf, medium or giant variety.
This hardy shrub can be identified by their long, shiny green, pointed leaves creating a full and dense appearance.
Throughout late spring and early summer, rhododendrons will be covered in a bright bloom of flowers, arranged in clusters of funnel shaped petals.
Most often these plants will be found in an array of reds, yellows, pinks, purples and whites, accompanied by a pleasant fragrance.
Where & when to plant rhododendrons
The best time of year to plant rhododendrons is in October, before the winter frosts begin, or in March to April, when the ground begins to warm up.
Regardless of whether you are planting your rhododendron into the ground or a container, you will want to ensure there is plenty of ericaceous soil mixed through, as they are partial to an acidic environment (between pH 5.0 and 6.0).
When planting your rhododendron, keep in mind that they are surface rooting and do not need to be planted deeply, just enough to cover the roots.
The optimum place to plant your rhododendrons is an area with shelter and dappled shade. Avoid planting them under tree canopies, as this can drench the plant in thick shade. Large varieties of rhododendron will withstand full sun if sheltered from cold, drying winds. Dwarf varieties of rhododendron will tolerate full sun, as long as the soil remains moist.
How to grow & care for rhododendrons
Watering – Rhododendrons thrive in soil that is well watered and will be best grown in an area that has high rainfall. Due to the high calcium content in tap water, it is best to water these shrubs with rain water where possible.
Feeding – When grown in an acid rich soil, rhododendrons will require little additional nutrients. If the soil is not at the right pH level, the rhododendron may suffer from deficiencies in magnesium, manganese or iron. Container planted rhododendrons will benefit from a slow release or liquid feed, where as plants in garden beds or borders may be better suited to a water soluble or powder feed. Always follow the instructions on the packaging for correct feeding.
Pruning – Rhododendrons require little maintenance when it comes to pruning or dead heading. To keep your plant looking neat and tidy, you can use a pair of secateurs to remove any unsightly faded or spent flower heads that haven’t yet fallen on their own, or any dead/weak growth that are reducing vigour or becoming an eyesore.
Common issues with rhododendrons
While rhododendrons are a hardy shrub, they may still suffer with common diseases.
Leaf drop – Mainly occurring after drought, you may notice the leaves rolling or dropping off. While this may look unsightly, once the ground has been well watered, the plant will begin to produce more leaves to give it back the dense appearance.
Leaf droop – Often occurring during extreme cold, the rhododendron may look less bold or bright as usual. While this is common during the winter months, once the ground begins to warm in spring, your plant will bounce back to life.
Non-flowering buds – Spells of particularly dry weather can result in poorly formed flower buds or no flower buds at all. To ensure this does not happen, add a layer of mulch around the base of the shrub and ensure to water well during summer, when rain is minimal.
Powdery mildew – A fungus growth on the surface of the leaf causing the leaf to turn reddish-purple or yellow. Provide plenty of space around the plant for air circulation and feed with a good quality slow release fertiliser to avoid this.
