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.
Flowering: fabulous, large tubular flowers in late winter and spring.
Feeding: regular feeding with a balanced azalea fertiliser.
Watering: rhododendrons require reliable watering.
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.
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 rhododendrons
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.
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.
There are many places to admire rhododendrons across New Zealand including one of the world’s biggest and most diverse collections at Pukeiti in New Plymouth, and Heritage Park in Kimbolton, near Palmerston North.
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.
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.
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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