What you need to know about rhododendrons
Name: rhododendron. rhododendron species and varieties.
Height: varies according to variety but from around one metre up to 4m plus.
Foliage: usually evergreen. Some deciduous forms occur.
Climate: cold temperate, warm temperate, subtropical and tropical.
Soil: prefer deep, well-drained soil but adaptable to most soil types except really dry spots.
Position: shade.
Flowering: fabulous, large tubular flowers in late winter and spring.
Feeding: regular feeding with a balanced, azalea fertiliser
Watering: rhododendrons require reliable watering.
Appearance of rhodedendrons
Rhododendrons are small to large evergreen shrubs with a rounded form with the bush being generally about as wide as it is tall.
Individually the flowers are like trumpets, but they appear in large groups to form almost a ball. They occur at the extremities of the plant, which makes them very prominent. Flowers come in just about every colour imaginable, from white through to deep purple. Flowering varies according to the variety, but there are forms that start in late winter and others that flower in the spring.
Uses for rhododendrons
The fantastic flowers are the main reason for growing rhododendrons. However, as evergreen shrubs they can also be used to screen fences, buildings and the less attractive parts of the garden. Smaller forms can also be grown in containers.
How to plant and grow rhododendrons
How to plant rhododendrons
- Plant out your rhododendron in autumn or winter before it flowers.
- If you have purchased it in flower don’t worry. Just enjoy the flowers and plant it as soon as the flowering has finished.
- Avoid planting at the hottest times of the year.
Soil
These plants like a soil that is on the slightly acid side. If you are not sure what type of soil you have then doing a test using a soil pH test kit will show you. Add plenty of rotted compost to the soil as the fibrous roots love organic matter.
Climate
A cool climate is best for most rhododendrons. In fact, most rhododendrons will tolerate heavy frosts and even snow! However, there are some rhododendrons – like the vireyas – that are adapted to tropical and sub-tropical conditions. So there really are rhododendrons for most places except the really arid areas.
Geographic area
There are many places to admire Rhododendrons across Australia. The Dandenong Ranges Botanic Garden (formerly the National Rhododendron Garden) in Victoria has over 15,000 rhododendrons to admire. In New South Wales there is the Blackheath Rhododendron Festivalthat celebrates the arrival of the spring bloom. Similarly Tasmania also has its own dedicated rhododendron garden at the Emu Valley Rhododendron Garden
How to care for your rhododendron
It is important to remember that this plant is naturally adapted to very dry conditions, so you can let it dry out considerably between waterings.
Diseases and pests
Watch out for signs that the leaves are starting to pale in sections or turn silver. This is a sign that they are under attack from sap- sucking insects such as lacebug, mites, whitefly, thrips or scale. Use a garden insecticide targeted for sap suckers and make sure to spray under the foliage.
Some varieties of rhododendron are susceptible to a fungus called petal blight that attacks the flowers and turns them into a sticky brown mess. If you see small brown spots appear on the flowers then remove all flowers to prevent the disease spreading and multiplying. The following year spray your plants with a fungicide as a preventative about late winter, but particularly as soon as the flower buds begin to show colour.
Growing rhododendrons from cuttings
1. Take cuttings from new growth, about ten to fifteen centimetres long.
2. Strip off all foliage except that at the very tip and take a two centimetre sliver off the bottom of the cutting.
3. Dip the cuttings in rooting hormone and place into a pot of propagating sand.
4. Pot the rooted cuttings into individual containers after about three months, taking extra care not to damage the new roots.
If you like this then try
Azalea: Small rhododendrons that will fit in most gardens.
Magnolia: Showy saucer flowers are a highlight of this small tree.
Agave: a group of succulents with a similar appearance to aloes.
Camellia: Evergreen dense shrubs with bright flowers in late winter and spring.
Waratah:Clusters of bright red flowers at the growing tips on a bushy evergreen shrub.
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