Azaleas maybe aren’t as popular as they used to be 10 or 20 years ago. I’m not sure why this is, because there’s lots to like about these lovely flowering shrubs. They don’t get too big, and they flower profusely over a long period, often a couple of times a year. They are at their most spectacular in spring, when the bushes may be so smothered in flowers that the foliage is completely hidden. But they may start to flower in autumn, continue through winter, and then finish with a final flourish in spring.
The flowers may be single or double, very large or quite small, and are held in clusters. The colour palette ranges from white through pastel pinks and into bold reds, oranges and purples. The plant size can vary from the miniatures, only 30cm high, right through to large 2.5m shrubs.
Most azaleas prefer part or dappled shade, although some varieties, usually those bearing single flowers, will grow in full sun. They love a well-drained, slightly acidic soil which is rich in organic matter. Azaleas are quite shallow rooted, so they benefit from a layer of mulch to help keep the root zone cool and to conserve moisture. They grow beautifully in pots, and can even be enjoyed indoors for a few weeks during flowering time. If you’re growing your azaleas in pots, make sure you use a specific azalea potting mix and choose a pot that isn’t too big for the plant. The miniature forms are often used in bonsai.
After flowering is finished, usually in late spring, cut them back by about one third, and apply a suitable fertilizer at the recommended rate.
Azaleas are a great choice if you need to add some colour in the dappled shade cast by established trees. They look quite at home in Japanese-style gardens as well as classical, cottage and country gardens. Combine them with camellias, gardenias, Plectranthus ‘Mona Lavender’ or cliveas. Plant them en masse to achieve a sensational spring show.
While they are easy to grow, they aren’t completely pest-free. Loss of colour, or silvering, in the leaves is usually the work of the tiny azalea lace bug. They suck the sap out of the leaves, which may then fall prematurely. If the infestation becomes very severe, it may kill the plant. We used to recommend Confidor to treat this, but now that we know that Confidor is toxic to bees, I don’t think we should be using it. Neem oil sprays have been effective in trials, so that’s what I’d be using instead. Azaleas growing in hot, sunny positions are more susceptible to attack from lace bug and other insects, so you can limit the damage by providing ideal growing conditions. Natural predators of azalea lace bugs include assassin bugs, lacewing larvae and lady beetles, so encourage them into your garden by limiting pesticide use and cultivating plants that will attract them.
Petal blight is the other most common problem. This is a fungal condition which causes the flowers to turn brown and mushy. Reduce the risk by avoiding overhead watering, and treat it if necessary with Eco-Fungicide.
Azaleas will last for years in a garden if they are planted in the right spot, and will put on a dazzling display every year.