Rhododendrons and Azaleas are amongst our best-loved garden plants. Each spring, these popular shrubs put on a spectacular and long-lasting display of colourful flowers. For flower to leaf ratio, it is difficult to think of plants that perform any better than Rhodos and Azaleas.
Although they’re most commonly seen in cool climate and temperate gardens; choose the right varieties and you can grow them in warm, humid climates as well. There are rhododendrons that occur naturally in the snow-covered Himalayas, and others from tropical south east Asia; there is even one that is native to the tropical rainforests of Australia.
There are several hundred species of Rhododendrons, and literally thousands of cultivars. There are both deciduous and evergreen types, and their size can vary from dwarf shrubs of 0.5 metre tall to trees over 20 metres in height.
What are Azaleas?Rhododendrons and Azaleas are very similar plants, both belonging to the family Ericaceae, in the genus Rhododendron.
Most of the commonly cultivated Rhododendrons are hybrids. This means they have been produced by crossing two different species together.
Azaleas are hybrids which are produced mostly from four Rhododendron species (and occasionally others).
Azaleas are generally classified into the following 3 types:
- Mollis azaleas – deciduous types; best for cool, rich soil.
- Indica azaleas – have more showy and larger flowers.
- Kurume azaleas – have smaller less showy flowers (but often a greater number of individual flowers).
What to grow in the tropics?The tropical rhododendrons are classified as Vireyas. Most of these are relatively small (some less than 1m tall, others perhaps to 2m). An Australian species, Rhodendron lochae, is native to North Queensland.
What to grow in the Sub-Tropics?As well as the Vireyas, Indica type azaleas will grow well in the sub tropics.
What to grow in Temperate Climates?
- Mollis, indica and kurume Azaleas.
- Many larger Rhodos and rock Rhodos.
- Vireyas are more difficult and slower to grow but can still be grown in a protected position such as a greenhouse or under the canopy of trees.
Growing Rhododendrons and AzaleasIn general, Rhodos and Azaleas will do best with:
- Acid soil (generally pH 5.5 – 6)
- Good drainage but also a moist soil.
- Ideally soil which is rich in organic matter. Mulching is beneficial.
- Protection from extreme heat. Semi-shade is ideal. Be aware that if planted under deciduous trees, the fibrous root system of the tree can compete with the rhododendron for moisture and nutrients. If the situation is too dark, the plant can become leggy and may not flower well. Some azaleas are labeled as ‘sun hardy’ but even these prefer semi-shade.
- Avoid digging around the Rhodo as they have shallow roots which can be disturbed.
- Pruning –
- remove dead flowers and dead wood regularly.
- Light shearing after flowering will keep them in shape.
- Heavy cutting is tolerated but this is generally only carried out to reshape or rejuvenate the plant.
- Feeding –
- Rhodos respond to regular feeding
- Ideally well rotted animal manure.
- The most cold-hardy azaleas are the deciduous Mollis varieties.
- Rhodos need shelter from strong wind.
TIPSome Rhododendrons are fragrant. Check the label before buying.
Places to Visit
- The Rhododendron Garden, Olinda, in the Dandenong Ranges of Victoria, Australia.
Probably the best public Rhodo garden in Australia.
For more information, go to their website. - Pukeiti Garden, near New Plymouth, New Zealand
The largest collection in NZ – something in flower all year round.
Visit their website.
AZALEA AND RHODODENDRON CORRESPONDENCE COURSEAustralian Correspondence Schools offers a course on Azaleas and Rhododendrons. This course can be undertaken from any country in the world.
For more information, go to
http://www.acsgarden.com/courses/azaleas-and-rhododendrons-541.aspx
If you would like to communicate with one of our professional tutors, consider using our free career counselling service, to help you decide of a learning and career development direction that is tailored to your needs. click for details
If you want to browse our bookshop, go to www.acsbookshop.com
VISIT OUR ACS ONLINE E BOOKSTORE
- Quality ebooks written by our staff
- Wide range of Horticulture titles by John Mason, author of over 40 gardening books, garden magazine editor, nurseryman, landscaper and principal of ACS.
- Ebooks can be purchased online and downloaded straight away.
- Read on an ipad, computer, iphone, reader or similar device.
- New titles published every month –bookmark and revisit this site regularly
- Download sample pages for free, to see what each book is like.
Titles include:
Commercial Hydroponics 3rd edition
One of the worlds best selling hydroponic books, first published in 1991 by Kangaroo Press. Dozens of colour photos, unique and rarely published advice on how to grow over 100 different types of plants (vegetables, herbs, flowers, indoor plants) in hydroponics.
http://www.acsebook.com/products/2232-commercial-hydroponics-third-edition.aspx
The Environment of Play 2
nd edition
A unique and inspirational view of designing play spaces for children. Full of photos, an inspiration for parents, child care workers, teachers, play leaders, landscape designers and park management professionals. First edition was published in the 1980’s by Leisure Press in New York.
http://www.acsebook.com/products/2247-the-environment-of-play.aspx
Trees and Shrubs for Warm Places First edition
A valuable reference for growing plants not only in the tropics and sub tropics, but also greenhouses, inside the home or even hot courtyards in a temperate garden. Never before been published. The book contains colour photos of close to 300 plants and descriptions of many times that number (and largely different to the plants covered in our Tropical Plants book).
http://acsebook.com/products/2238-trees-and-shrubs-for-warm-placescoming-soon.aspx
Garden Design Part 2 1
st edition
Following on from Garden Design Part 1, this presents approximately 300 more photos, and a huge amount of inspirational reading to help you (in particular), understand the different styles of garden and the options open to you as a garden designer, or a home owner.
http://acsebook.com/products/2244-garden-design-part-2.aspx
Discounts offered for students of ACS Distance Education
