The most commonly asked question that I get asked everywhere I go is how to grow azaleas. Here is a repeat (a revised edition) of the things that I do, with success, on how to grow and get these beautiful shrubs to flower and keep alive. I keep hearing, ‘I had an azalea but it died!’ Well, here is my personal experience on growing these fabulous trees which I have done for many, many years with success. I hope you can get something from this article and maybe we may be able to see more and more azaleas displayed at bonsai shows. I know they are one of my favourite trees to grow.
Rose fanciers please start reading from the next paragraph, for everyone else please continue. ‘An azalea, is an azalea, is an azalea……….’ to rephrase a popular saying. What other plant puts on a more magnificent show than these shrubs when they are in full bloom? They are in just about every garden from the mountains to the sea, in nearly every colour imaginable and ranging from just a few inches high to massive trees (Rhododendrons). In the wild they grow in full sun, dappled shade and there are even a few that are epiphytes (Vireyas), meaning that they grow in the forks of other trees, clinging to branches, on rocks or on the side of cliffs. They are found from the foothills at sea level to a height of about 18,000 feet. The word ‘rhododendron’, loosely translated means ‘rose tree’, so I don’t think I can be out of favour with rose growers too much – can I?
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. There were a few wild varieties (azaleas) found in Japan and in North America, but it has only been in the last 200-300 years that explorers have collected and distributed many specimens from the east to botanists, and hybridizing has produced many hundreds and hundreds of varieties that we know of and love today.
When azaleas arrived in Europe, they were named Azalea from the Greek word ‘Azaleos’, meaning arid, in reference to the type of dry mountain soil they grow in with decaying mulch to protect the fine fibrous roots.
To save confusion, from now on I will only describe and speak of azaleas, the shrubs that we use for gardens, in pots and for bonsai.
When azaleas arrived in Europe and England it was the botanists that wanted to raise hybrids that would be used as floral potted plants for indoor use and for growing in greenhouses. These plants were primarily raised and forced into flower for home decoration and then discarded, as they would not grow in the harsh European winters. It was then in the early 1800s that the Belgians were the chief producers of the plants known today as Belgian Indica azaleas that were hardier, evergreen and produced double and semi double flowers. Similar hybridizing work was carried out by botanists in England, America and Japan and they can also claim their fame in the varieties that they have produced. England for their Knap Hill, Exbury and Illam hybrids, America the Rutherford and Kerrigan, and Japan for Kusianum, Kurume and Satsukis to name but a few, and I can assure you the list goes on and on.
Satsuki azaleas, I think are a subject all of their own, but briefly these azaleas are highly revered in Japan and there are hundreds of clubs specializing in these azaleas as bonsai. The word Satsuki comes from the old Japanese translation of ‘fifth moon’, in other words relating to the flowering time which occurs around the fifth month of the oriental lunar calendar. On one satsuki azalea you often get between 2 and 5 different coloured flowers on the one bush. Botanically, satsuki azaleas are classed as unstable hence the high amount of ‘sporting’ (different coloured flowers), but the Japanese have used their difference as a specialized art form.
There is another satsuki from the Mie prefecture that is only used as hedging in Japanese gardens. These are trained into the rounded mounds so often seen in these gardens and their claim to fame is that they respond so well to pruning and have magnificent bronze, new growth in winter. The flowers are not generally the focal point as they are just a plain single pink; it is the bronze foliage that comes to the fore.
So far, the azaleas mentioned are evergreens, but there are the deciduous ones that grow in the cooler districts that have a spindly growth pattern and have brightly coloured flowers in yellow, orange, apricot, green, red and mauve and are also perfumed, whereas the evergreens come in white, pink and red and most are not perfumed.
Evergreen azaleas have, I think, a magnificent way of growing naturally without ever being pruned (especially the kurumes and gumpos), and when in flower just stand back and look at the overall shape of the whole shrub to understand what I mean. The large Indica azaleas grown in most gardens here in Sydney, take on the appearance of a billowing cloud and it is accentuated what I mean when it is covered in flowers. In a massed display of different coloured flowers in the wild it seems that the mountain sides are covered in multi coloured clouds. Just look around your neighbourhood and you will see azaleas totally neglected; yet they still take on a very pleasing and natural shape and often flower very well on near neglect.
For many years I have grown azaleas in bonsai pots and every year I am rewarded with beautiful blooms set against bright fresh green foliage and I can guarantee they are not as ‘finicky’ as maybe you have been led to believe. They grow in full sun all year round, get watered by the watering system and get repotted on an average every 1 to 2 years. They strike readily from long cuttings, will keep indoors while in flower for quite a long time, shoot back on old wood, easy to train – what more could you expect from a magnificent specimen to work with. There is only one drawback and that is the flowers have no perfume but with all the other good points I don’t mind the trade-off. The types I have grown and had success with are gumpos (small up to 12 inches), kurumes, indicas, satsukis, kusianum and Belgian indicas, and a few others.
I have prepared some cultural notes 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, that you too can be successful.
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.
The Japanese grow azaleas in calcined clay. Now calcined clay is low fired clay which is fired to about 900 degrees then it is crushed to different sizes ranging from breadcrumb size to about pea size. This then results in a porous moisture retentive vehicle to supply a constant supply of moisture to the fibrous roots.
FERTILISER – Azaleas require an acid soil and after they have settled down after repotting I use Osmocote slow release specifically for azaleas and rhododendrons. Seasol is another product I use especially after repotting if I think that the root system needs an extra boost. Seaweed solutions contain elements known as mannitol and alginic acid, which helps to acidify the soil and helps the plant to absorb nutrients. Especially good for azaleas, camellias, gardenias, and pieris etc. i.e. any acid loving plants. If the soil is too alkaline, it will be difficult for azaleas to take up iron and magnesium.
If you are not happy with the amount of flowers you get, you can give a couple of doses through the year (especially after Christmas up until May of every year) or Phostrogen, More Bloom or Bloom Buster (usually used for orchids), but be warned, follow manufacturer’s directions closely or if in doubt lower the dosage. The product I have had a lot of success with is Liquid Potash by Manutec – it is a pink liquid that you add to water and it is specifically to induce flowers and fruit on your fruiting and flowering trees. Remember to follow the instructions on the container on any of the products you use for not only azaleas but for all your trees. You need to study the NPK’s on the label of fertilizers and what you are looking for is a very high ‘K’ (Potassium) level to ensure lots of flowers. This will also improve flower quality and quantity.
After flowering feed with your normal nitrogen enriched fertilizer to give back energy to the tree after all the work of producing all those flowers, then as stated after December feed with the high potassium fertilizer. I also use at times, Nitrosol which is an organic fertilizer which also has a high potassium level and also has liquid blood and bone which is beneficial for all aspects of growing the trees healthily and I use this from after flowering up until December.
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 ‘silvery’ 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. When these trees are in flower they can be bought inside for a short period, but as soon as the flowers wilt, return outside and remove the old flowers and seed pods.
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.
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.
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 if not applied on the surface.
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. To complete your bench display you could also add some small camellia bonsais that enjoy exactly the same conditions and perform just as well. You could be the envy of your friends with all of those beautiful flowers.
DID YOU KNOW? – The first botanical book in Japan was called “Motokatsu” Mizuno written in 1681 and contained 147 varieties of indigenous azaleas. The first books on azaleas called ‘Kinshuku makura’ was published about 1692 by Ihei Ito in five volumes and contained references to about 350 azaleas.
• Satsuki azaleas are less hardy than most azaleas and have a low and twiggy habit and have funnel shaped single flowers. They flower in late spring to early summer not like other varieties that flower in winter to spring.
• Kurumes are hardier than most azaleas and can be grown in full sun in gardens.
• Gumpos make great garden specimens and have large single flowers in white, pink and a light cerise. They are very low growing and make more growth on the lower branches and only reach up to about 200mm. The flowers have a frilly edge to them.
• R. Kusianum (Kyushu Azalea) is the father of the Kurume azaleas and used for hybridizing. These are semi to full deciduous types.
• You may recognize some of the names of azaleas and where they were developed. Belgium Hybrids – Comtesse de Kerchove, Elsa Kaerger, Hexe, Leopold Astrid, Paul Schaeme, Red Poppy, Red Wing, Rosa Belton, Southern Aurora, Violacea and the one pictured below is one of mine called Mdme. Auguste Haaerens.
• Rutherford Indicas (developed in USA) – Dorothy Gish, Rose Queen.
• Satsuki – Chojuho (treasure of longevity) – flowers stay on for most of the year and fade to a lighter colour.
• Kerrigan Indicas (USA derived form of Belgium Hybrids) – Brides Bouquet, Ripples.
• Indicum & Mucronatum Hybrids – Balsaminaeflora.
• Kurumes (Japan) – Blaauw’s Pink, Christmas Cheer, Fairy Queen, Kirin, Ward’s Ruby.
• Gumpos – dwarf shrubs smothered in single flowers with frilly edges.
• August Kehr Hybrids (USA) – Anna Kehr, White Rosebud.
• Nuccio Hybrids (USA) – Purple Glitters and Rose Glitters.
NOTE: For the first time in Kokufu-ten history in Japan, azaleas are now allowed to be included in the formal display.
Colours of Azaleas in My Garden
Merge and mingle pretty flowers from your mountains far away –
You have brought the blue of summer and the golden of a day.
You have brought the scarlet sunset and the white eternal snow;
You have brought the purple night time and the fresh pink morning glow.
You have brought the orange fireball from above the noon-day skies
And mixed them all in blossoms before my wondering eyes.