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Where to Grow | How to Plant | Best Soils | When to Plant | How to Care for Azaleas | Problem Solving | Advice on Buying | Advice for Your Garden | Further Reading
Where to Grow Azaleas
Although they are woodland plants that enjoy the shade, many azaleas can cope with some sunshine in a mixed border and will liven up a North-facing wall or gloomy corner to no end. That’s not to say they don’t look great in pots - they look fabulous as focal accents around the garden or patio.
Tender types can be grown indoors in a cool, well-ventilated room such as a conservatory or porch. Position them somewhere sunny, making sure to keep them out of direct sunlight as it can scorch the foliage.
How to Plant Azaleas
Large azaleas aren’t temporary lodgers. You’ll need to think hard about where to plant them. If you can provide their exact requirements, you will be rewarded with joyful explosions of spring flowers for years to come, so it’s worth taking time to plant them carefully.
● Give your new plant a good drink and let it drain whilst you dig a planting hole.
● Azaleas are shallow-rooted, so make sure the hole is wider and slightly deeper than its pot. placing the plant so it sits just beneath the surface of the soil. Backfill with a mix of leaf mould and ericaceous compost and water it again for good measure.
● Mulch azaleas annually with an acidic blend of leaf mould, peat-free ericaceous compost, or any kind of conifer litter.
Best Soil for Azaleas
With few exceptions, azaleas love moist, humus-rich, and well-drained acidic soil. Just about all azaleas are lime haters and will struggle in clay soil.
If you’re unable to provide these conditions, be prepared to try to improve your soil because there is nothing worse than trying to grow a constantly sulking shrub. Azaleas like moist acid soil (pH 3.5 - 6.0) although some deciduous azaleas will tolerate pH 6.5.
Adding organic matter, such as compost or well-rotted manure can help acidify clay soil and sandy soils but be prepared to do it annually. Peat-free ericaceous compost for pot-grown azaleas is widely available.
When to Plant Azaleas
The best times to plant azaleas are spring and autumn. Position them in partial shade or full sun for best results.
Plant azaleas in borders, lining shadowy paths and driveways. Those with little or no outdoor space can grow compact indoor azaleas in conservatories in bright light, (but not direct sunlight).
How to Care for Azaleas
Mulch outdoor azaleas annually with an acidic mulch of leaf mould or pine/conifer bark litter. If you’re growing them in woodland areas that are home to pine trees or other conifers, the annual leaf fall will rot down and provide nature’s own acidic mulch, so you can skip this task.
If you’re growing pot-grown and indoor azaleas, you’ll need to replace the top layer of compost each spring with ericaceous compost and in some cases, repot plants completely when you notice they aren’t flowering as well as they used to.
Keep compost moist but not waterlogged. Collect rainwater, if possible, as tap water tends to be alkaline. Feed plants weekly with a specialist ericaceous fertiliser.
Indoor plants benefit from deadheading to entice them to bloom longer whereas outdoor plants don’t need deadheading and are best left to their own devices.
Pruning
You will be pleased to learn that Azaleas are low-maintenance shrubs and require little or no pruning.
However, if you’ve inherited a large azalea that has outgrown its space, is too tall or leggy and is threatening to swamp neighbouring plants, take the following steps to make it more manageable after the blossom has faded, but before new buds have formed. Don’t try to reduce a very large shrub in one hit as it can shock the plant. Instead cut out about 1/3 of the old wood over three years.
● Remove dead, diseased, or damaged branches at any time of year. Depending on the size of the branches, you can use either pruning shears, loppers, or a pruning saw.
● Broken branches should be cut just above a dormant bud and dead branches should be cut back to a branch point, where dormant buds can send out new growth.
● Interior branches that don’t receive any light may be removed because they will eventually die back.
● Diseased branches should be pruned well below any diseased area and disposed of immediately.
Watering
Azaleas loathe drying out and require moist, well-drained soil all year round. In winter, spring, and late autumn, British weather usually provides rain aplenty. However, be prepared to water once weekly during prolonged dry or hot spells.
Fertiliser & Mulching Azaleas
Azaleas are best mulched in spring each year, and all types appreciate mulch made up of acidic material, like leaf mould, pine needles, or conifer wood chips. These ingredients help to replenish nutrients in the soil and maintain the acidity required for them to thrive.
How to propagate azaleas
By far the easiest way to propagate azaleas is by taking semi-ripe heel cuttings from mid to late summer. Here's how to do it:
1. Have a plastic bag ready with a damp paper towel inside to collect your cuttings. Cuttings are best taken early in the morning when the stems and leaves are still full of water.
2. With a clean knife or secateurs, choose a non-flowering stem that you can pull away from the parent plant, taking a sliver of the main stem, the ‘heel’ with it.
3. Place cuttings in the bag to keep them fresh if you’re gathering more than one stem.
4. On a clean surface, cut a section of the stem just below a node (the part of a stem where leaves and buds grow). Ideally, cuttings should be about 10-15 cm long.
5. Strip off the lower leaves so you are left with a bare stem with two leaves on top. Cut each lead in half horizontally to minimise water loss from the leaves.
6. Fill a pot with gritty ericaceous compost and water it well before adding a fine layer of grit or gravel to the top of the compost.
7. The cutting should be firm enough for you to push the cut end into the pot, although you can use a chopstick to make a hole in the potting mix instead.
8. Firm the soil at the base of the cutting gently and label.
9. Repeat this process until you have potted up as many cuttings as you require.
10. Place the potted cuttings in a propagator. If you don’t have one, cover the pot with a clear plastic bag and leave it in a warm dry place out of direct sunlight. Cuttings taken in autumn benefit from being placed in a heated propagator.
Leave your cuttings to develop roots through autumn and winter, keeping the compost damp but not waterlogged as this causes the stems to rot. After three weeks, check if they have rooted - you’ll see roots coming through the holes in the bottom of the pot.
Remove any cuttings that haven’t rooted or have dried out as they are unlikely to grow. Rooted cuttings can now be moved into individual pots filled with fresh compost and watered.
Leave the new plants in their pots and again wait for their roots to come through the bottom of the pot. This can take four weeks or more when they are ready to be planted out into final positions in the ground or containers.
Growing Azaleas: Problem-solving
Like most shrubs, Azaleas are quite trouble-free and the most common problems you are likely to encounter are listed below so you know how to spot symptoms and deal with them.
Scale Insect
There are more than 25 species of scale insects that are active all year round and these sap-sucking, limpet-like bugs have protective shells that make them difficult to get rid of.
Symptoms: Look out for white egg masses on both the stems and the undersides of leaves, and on weak or poor young plant growth.
Treatment: Remove scale insects using a brush and warm soapy water or spray with an eco-insecticide.
Vine Weevil
Vine weevil, dull black beetles with pointed heads are active from spring to summer affecting Azaleas as well as many plants grown in containers. They eat leaves, leaving behind ugly notches but while the damage is unsightly, it’s rarely serious. However, it’s their larvae that pose far more serious injury to plants than adult weevils. Adult beetles lay their eggs in the soil of potted plants when small creamy grubs hatch and feed on plant roots which can cause the plant to collapse and die.
Symptoms: Leaves drop, or plants wilt or suddenly keel over.
Treatment: Upturn pot-grown plants and inspect the roots for grubs, pick them out and squash them.
Encourage hedgehogs, birds, frogs and toads to feed on the beetles. Nematodes are very effective when watered over pots from March to May and repeated from August to November. The temperature needs to be above 5°C to be effective. Nematodes release deadly bacteria that kill the grubs that should be enough to break the lifecycle.
Azalea Diseases
Azalea Gall:
It’s a fungal disease that is unsightly but rarely fatal. There are no fungicides available to home gardeners to control this disease, but Azalea galls are very visible so deal with the problem the moment you spot it.
Symptoms: Fleshy, odd-shaped pale green or pink growths (or galls ranging from pea-sized to about 7-8 cm) appear on leaves and/or flowers of both azaleas and rhododendrons. As summer arrives, they turn white with a floury bloom as spores are produced often engulfing both flowers and leaves.
Treatment: Buy strong, healthy plants and provide ideal growing conditions.
Galls should be removed, put in bags and destroyed as soon as they are seen. Don’t wait for spores to become airborne making the disease spread more rapidly. To prevent repeat infections, carefully pick off or prune out and dispose of affected leaves. Rake-up affected fallen leaves, especially in autumn to reduce the spread through winter.
Nutrient deficiency:
This is usually a sign of waterlogging or nutrient deficiency but can also be caused by overly alkaline conditions.
Symptoms: Yellowing leaves.
Treatment: Make sure your azaleas are growing in suitable acid soil.
Bud blast:
Rhododendron bud blast is a fungal disease spread by the rhododendron leafhopper and affects azaleas when the insect lays eggs on the developing flower buds of these plants.
Symptoms: Buds brown and die before turning a silvery colour and then are covered in black whiskers. Affected buds will fail to open and flower but the problem usually only affects a few of the buds so overall the plant will still flower well.
Treatment: Keep plants free of leafhoppers especially when the female adults are laying eggs from July to October using an eco-insecticide. Pick off any affected buds carefully making sure not to spread the disease from affected buds to unaffected ones and dispose of them in the bin - don’t add them to the compost heap.
Advice on Buying Azaleas
Azaleas are undoubtedly long-lasting and elegant additions to our gardens. Remember when choosing which ones to buy that some are deciduous, and others evergreen. The evergreens are incredibly useful for muffling traffic noise when planted en-masse if you live on a busy road and adding year-round privacy. If you’re looking for textural planting as well as a luxuriant flare of spring flowers, bear in mind some varieties are more cold-sensitive than others so are best for growing indoors in frost-free conservatories or porches.
Azaleas for Your Garden
Azaleas can be used in a variety of ways in the garden and landscape. They look stunning planted in drifts or grouped with other shade-loving shrubs with different flowering times to provide extended washes of colour or mix and match deciduous and evergreen azaleas together to enjoy their leaves tipped with frost.
Deciduous Azaleas
You might enjoy browsing some of our fabulous deciduous Azaleas to add the wow factor to your garden this spring.
Evergreen Azaleas
Add year-round texture and eye-popping colour to your garden by planting a fabulous evergreen Azalea this weekend.
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