The word ‘rhododendron’, loosely translated means ‘rose tree. Azaleas, rhododendrons and vireyas (tropical types) are all classed and known under the one family name – rhododendrons, and botanically there is no difference between them. They originated in China, the Himalayan Mountains and the cooler parts of south Asia and the first noted record of these plants dates back to 400 BC.
Cultivating Azalea Bonsai by Brenda Parker
These cultural notes have been prepared based on what I do in my situation, but there may be some adjustments you may have to do in your space, and only by trial and error and understanding how they grow and their simple requirements.
SOIL – Bonsai potting mix broken down with sharp river sand to make it very porous to allow oxygen to reach the roots. Forget using potting mixes with added peat moss if you have a watering system as the peat stays too moist and the soil then becomes rancid causing root rot. If you do use peat-based mixes in bonsai pots and forget to water a few days, the peat becomes very hard and will not allow water to penetrate to reach the roots and when the fine azalea roots dry out it means trouble. Maybe in a large garden pot it could be alright, but I am a bit wary in small pots. Remember they grow in well drained soil on mountain slopes in the wild only protected by decaying leaf litter.
FERTILIZER – Azaleas require an acid soil and after they have settled down after repotting. See the SCBC June Newsletter for detailed information on the types of fertiliser successfully used by Brenda in the Sydney region of Australia.
PEST AND DISEASES – I am still of the belief that if the soil is perfect the tree is healthy, but there is always that chance that these bugs come along to spoil your day.
When the weather starts to warm up (about mid September), I spray the underside and top of the leaves with Confidor or Sharp Shooter and continue to do this again in about mid October and then again in late December. This is a systemic spray to abate the red spider and lace bug that like to gnaw at the under surface of the leaves resulting in the leaves getting a ‘silver’ appearance. It looks unsightly but it will not harm the tree. When the new growth appears these old leaves usually are shed and are renewed all over again, but for displaying purposes, you would not display a tree in this condition.
Once the flowers emerge there is a fungal disease that makes the flowers wilt and turn very mushy. It is called petal blight and spraying with Bayleton at the time you start to see colour in the buds is a good time to stop or reduce it. This fungus attacks the base of the flower where the petals join the calyx and it is advisable to remove these damaged flowers and dispose of in the garbage bin, not in the compost bin, otherwise the problem will be compounded next year. When azaleas are in flower it is advisable only to water the soil level only and not the flowers, and usually when they are in flower my watering system is usually turned off.
Chlorosis is a condition where the leaves usually turn yellow with very defined green veins which indicate a lack of iron and/or magnesium. As the deficiency of iron or magnesium is hard to detect, mix 1oz. of iron sulphate (or iron chelates) and 1 oz. of magnesium sulphate (Epsom salts) in 5 litres of water and apply over foliage and soil surface.
STYLING – Azalea branches are very brittle and snap very easily. I only put wire on very flexible branches and then I put it on very loosely as they mark very easily. If a branch does snap (not completely off), use it to your advantage and tape over with sealant and then grafting tape – they heal really well. This is a unique way to make bends in a somewhat straight branch.
REPOTTING – You can repot an azalea at any time of the year even in full flower because of the fibrous root system. After repotting place the tree in a cool position and keep moist but not wet. A dose of Seasol helps with the disturbance of the roots. Ideally the best time to repot is after flowering in spring. I never add fertilizer when repotting only after when I can see new growth appearing. Only apply Osmocote on the soil surface and not under the tree in the pot. Azaleas are surface rooted and surface feeders and it will be only wasted out of the drainage holes.
PRUNING – Pruning is always carried out after flowering as with all other trees. If pruning is not carried out after every flowering, the natural growth habit of azaleas is that they get very leggy with foliage mainly at the tips. Tip pruning is continually carried out right up until Christmas and no later than to the end of January, as this is the time when buds are starting to form for the next flowering season. Remember to also remove any seed heads as this will weaken your tree.
PROPAGATION – The usual applies to azaleas, seeds (not common), cuttings, aerial layers, ground layering and of course dig-ups from old gardens or demolition sites, grafting etc. Cuttings are easy to strike and usually are taken in late December to early February, about 6-10cms long with only the leaves left at the tip, placed in a mix of very sandy soil and lots crammed into a 10cm pot, watered and kept in a very damp and semi shaded spot in a fern or shade house. I don’t usually cover the cuttings with a plastic bag as my shade house is always damp and humid and my success rate is very high.
POTS – These are usually deeper than most and coloured to compliment the flowers. Remember that deep pots drain better than shallow pots.
I hope that my experience with azaleas will entice you to try some for yourselves and I am sure with great success. They are such a diverse group of plants that you will be enthralled with them for many years.