Astonishing Azaleas: How to Grow a Signature Azalea Shrub

If you’re looking for a spring-blooming shrub with stunning, showy blooms and a low-maintenance temperament, look no further than the Azalea! Perfect for laid-back gardeners seeking a fuss-free celebration of colour year after year, these long-lived acid-loving plants are simply irresistible.

Learn all there is to know about growing and caring for them with our ultimate guide to awesome azaleas.

What are Azaleas?

Azalea is a huge and diverse group of perennial flowering shrubs which belong to the Rhododendron genus. There are around 800 different species of azalea and a further 10,000 different cultivars, making it one of the most extensively hybridised, and thus varied, groups of plants on the planet. Members of the Ericaceae family of acid-loving plants, azaleas are related to Heathers, Blueberries, and Cranberries.

Azaleas are now naturalised to a variety of environments, climates, and conditions across Asia, North America, and Europe, although they originally hail from temperate and cool regions of Japan and China.

In the northern hemisphere, azaleas usually bloom from early to late spring, whilst in the southern hemisphere, they bloom during late autumn and early winter. There are even some varieties with a re-blooming period later in the year. Originating from a single ancestor which first evolved around 70 million years ago, Azaleas had been bred selectively for hundreds of years by Buddhist monks before being introduced to Europe and the Americas.

As is to be expected in such a large and varied genus, azaleas are available in all manner of growth habits, ranging from dwarf varieties as small as twelve inches tall to tree-like varieties reaching well over ten feet in height. Although each variety’s flower is unique, most azalea blooms feature five or six central stamens typically framed by five to seven petals, although some species have up to twelve petals and up to ten stamens.

Flowers range from simple single-flowered types to intricate double and semi-double types, some with ruffled or frilled petals, some with flat, open faces, and others with slender, tubular flowers. Even the markings on the petals vary between species, with some being singularly coloured, others with speckled or striped patterns, and others with sectored or graduated colour markings.

And as you might have guessed, these diverse plants produce blooms in almost every colour imaginable, and some varieties are even capable of producing more than one flower colour on a single bush!

What do Azaleas symbolise? 

Like many plants with such a wide geographical spread and long, rich history, the azalea has been ascribed a variety of different meanings by different cultures over time.

In Chinese culture, the azalea bush is often used to represent femininity and womanhood. It is also nicknamed “the thinking bush” in China because of its association with thoughtfulness and pensiveness.

In the Victorian Language of Flowers, the azalea symbolised temperance, prudence, and modesty. In other cultures, however, the azalea has been ascribed an altogether more sinister meaning. Because of its toxicity to humans if consumed, giving someone an azalea in a black vase as a gift can be interpreted as a death threat! In astrology, the azalea is the flower of the Sagittarius star sign.

Types of Azalea

Although there are over 800 different species of azalea, and many thousands more cultivars, they can more or less all be neatly categorised into one of two groups; deciduous or evergreen. 

Deciduous or pentanthera azaleas loose their foliage in the winter. Many deciduous species undergo a process of fiery transformation during autumn, whereby the leaves transition from a glossy green to a deep rust colour before shedding. In spring, fresh new foliage will emerge. 

Evergreen or tsutsusi azaleas hold their foliage all year round. The leaves remain the same colour throughout all four seasons, and simply regenerate through a continuous cycle of replacing a few leaves at a time.

Some varieties can become semi-evergreen or semi-deciduous if they are grown in a climate that is vastly different to their natural habitat, or during periods of extreme and unusual weather.  

Within the Tsutsusi and Pentanthera subgenera, azaleas can be further categorised into a whole range of smaller subgroups and hybrids, depending on growth habits, size, blooming time, and flower types. Here are nine of the best and most beautiful subgroups of azalea that you might like to grow.

1. Aromi azaleas were developed in the 1970s, and are early bloomers, with large, showy flowers. These deciduous varieties lose their leaves in autumn and winter, but having been first bred in the hot, dry Arizona climate to be heat and drought-tolerant, they prefer a warm, full-sun position in the garden. The aromi azalea group boasts a huge variety of blooms, some double-flowers, some multi-coloured, and some rose-like, meaning there’s plenty of choice with an aromi azalea, especially if you need to fill a full sun space in your garden.
2. Dodd Confederate azaleas were developed with heat tolerance in mind, although they produce their best blooms in a partial shade position. This deciduous group boasts some of the most breathtaking and intricate azalea flowers, many with scalloped petals and multi-tonal hues. There are eleven exquisitely beautiful azaleas to choose from in this group, and each one is a sure show-stopper for any warm garden.
3. Glenn Dale hybrids have been created to have a late blooming period, large showy flowers, and are cold-resistant. There are over 450 individual azaleas within the Glenn Dale group, ranging from dwarf varieties to trees reaching a towering eight feet tall. Blooming anywhere from early April until late June, they are available in a huge range of flower types and colours. You are spoilt for choice with Glenn Dale azaleas.
4. Holly Springs are hybrid evergreen azaleas that were developed in the USA to have large blooms and a small to medium-sized growth habit. They boast wide open flowers in shades of pink and purple, many of which have ruffled petals and contrasting gold-coloured stamens, reminiscent of tropical hibiscus flowers. There are over 80 stunning Holly Springs varieties to choose from, and their impressive cold tolerance makes them a great choice for a cool northern garden.
5. Kurume azaleas are an evergreen dwarf group which have been developed to be cold-resistant. They generally have a compact and slow growth pattern, reaching around four feet tall at full maturity, and usually spread wider than they are tall. Generally blooming during spring, they produce all sorts of flower types and colours, so there are plenty of options for you to choose from. Kurume azaleas like a partial sun or dappled shade position, and they are sensitive to both periods of drought and overwatering.
6. Kyushu varieties are some of the hardiest azaleas available. Native to mountainous regions of Japan, they can tolerate a range of light conditions and temperatures. They produce an abundance of moderately sized blooms in various shades of pink. Depending on the region they are grown, these adaptable azaleas can be either true evergreens or semi-evergreens, and have a compact height, with dense foliage and a wide spread, making them ideal for ground cover.
7. Satsuki azaleas are popular hybrids which first emerged in Japan over 500 years ago. They are somewhat unique amongst azaleas in that a single shrub can produce flowers of many different colours. They are a relatively late-blooming group, usually flowering between May and July. Although normally growing to around five feet in height, some Satsuki azaleas have been developed even further to create bonsai-sized plants. This variety is fairly cold-tolerant and prefers a semi-shade position.
8. Southern Indica azaleas are an early-blooming, semi-evergreen group. They offer beautiful blooms in a huge range of colours from pale yellows to bright purples. These hybrids have a fast growth habit, easily reaching around ten feet tall when mature, although some smaller varieties are commonly grown as houseplants. Southern Indica azaleas are not particularly cold hardy or heat tolerant, so need a sheltered position in the garden, and may need extra protection over winter in cooler climates, as frost can kill them.
9. Swamp azaleas are famed for their powerful floral, almost spicy fragrance. Originating from the swamps and wetlands of North America, they offer delicate funnel-shaped white and pink flowers. They are relatively late bloomers, usually flowering in summer, and have a compact, dense growth habit and wide spread. Unlike most other azalea species, the swamp variety can tolerate wetter soil conditions, so long as it is well-draining. 
   

How to grow Azalea from seed 

Azaleas are relatively easy to grow from seed, although they do need a little special attention to get them started, and they’re unlikely to bloom for several years. The seeds are readily available from garden centres and nurseries, or you could collect seeds from the pods of mature plants. The best time to collect seeds is in the autumn once they have dried out but just before they begin to split. 

To start your azalea from seeds: 

1. Fill a seed tray with a mixture of half sphagnum moss and half perlite. Sprinkle the seeds over the substrate evenly.
2. Lightly moisten the substrate with a mister and cover the tray with clear plastic wrap to create a warm, humid microclimate.
3. Place the tray on a sunny windowsill. Germination should begin after around four weeks.
4. Once sprouted, the plastic wrap can be removed and the substrate kept lightly moist until the seedlings have developed at least two true leaves.
5. Transplant the seedlings into individual pots filled with the same substrate as you used for the seeds.
6. Keep them in a warm, humid, place with plenty of indirect light to help them become established over the remainder of the winter.
7. After the last frost has passed, you can gradually acclimatise your new azaleas to outdoor conditions, before transplanting them to their intended growing position.

How to care for Azalea

When to plant azalea 

The best time to plant a young azalea is in autumn when the weather is cool but not freezing and the days are still bright. This gives them plenty of time to develop healthy roots ready for spring blooming. If you want a specific bloom colour from your azalea, wait until spring before purchasing anything, as the buds will already be developing and you will be able to see exactly what colour flowers to expect.

Pots and Positioning 

Dwarf azalea varieties, and those with a moderate size and spread, are ideal for pots and containers. You can grow even larger varieties in pots as long as you prune them regularly. Azaleas are shallow-rooted, so they don’t need a very deep pot, but it must be wide enough to accommodate their root ball, with plenty of room to grow. Plenty of drainage holes are a must!

In borders, give your azaleas plenty of space to accommodate their eventual mature spread. This can be anywhere from two to six feet depending on your chosen species. When digging a hole for your azalea, don’t bury the root ball too deep. Ensure it sits flush with the surface of the soil to avoid its shallow root system sinking too far down over time and becoming oversaturated with surface water.

Soil

The key thing to remember with azaleas is that they must be grown in acidic soil with a pH level between 4.5 and 6.0. It can be tricky to achieve the consistent acidity they require, especially if your soil is naturally alkaline. You can amend alkaline soil to create a more acidic environment using mulches containing pine, coffee grounds, or sphagnum moss, or by adding sulphur-rich enhancements.

Soil amendment on this scale is an ongoing process and can be laborious, requiring regular upkeep, which is why many people chose to grow them in pots using ericaceous compost. Attempting to grow azaleas in alkaline soil will lead to nutrient deficiencies and eventual death. Mulching regularly with acidic matter will also help to protect your azalea’s shallow root systems.

Secondly, azaleas will not tolerate heavy, wet soils and waterlogged roots, so they need a light, loose, exceptionally well-draining substrate. Don’t attempt to grow azalea in clay soil types, and work through extra drainage materials even in looser soils to promote aeration.

Light

Light requirements for azaleas vary from species to species, so try to choose a variety which is well-suited to the conditions in your garden. As a general rule, most azaleas perform best in a position with partial or dappled shade, though some deciduous species will struggle to bloom in heavy shade. You can probably get away with planting your azalea in a full-sun position if you live in a northern climate where the sun’s rays are less intense.

Water 

Once established, your azalea will be able to tolerate short periods of drought, but younger plants will need more regular watering as they mature. Aim to keep your azaleas soil very lightly and evenly moist to avoid stressing the roots. Mature plants need around an inch of water per week. Azaleas planted in shady positions will need less water than those in sunnier positions. Always allow container-grown azaleas to drain thoroughly after watering. If possible, you should try to collect rainwater for your azaleas, since tap water can be quite alkaline. 

Food 

Azaleas can be prone to nutrient deficiencies because their shallow roots aren’t able to extract nutrients from deep below the surface of the soil. They can also become nutrient deficient if planted in alkaline soil. This being said, don’t be tempted to over-fertilise your azalea. Instead, make sure they are planted in a hummus-rich, fertile substrate, and supplement this only in late spring using a specialist ericaceous plant food, just after they have finished blooming. Avoid feeding any of your azaleas until they are properly established. 

Pruning 

The great thing about azaleas is that they require very little maintenance once matured. Generally, pruning isn’t essential, but this will depend on your variety, and of course, on your own personal preference. Deadheading spent blooms and a general prune right after flowering has finished will help them to develop lots of new flower buds ready for the following year. As they age, azaleas can become woody and spindly, so cutting them right back by about a third just after flowering will also help to rejuvenate their vigour and density. Excessively pruning your azalea every year can actually do more harm than good though, so try not to get too scissor-happy! 

Overwintering 

The majority of azalea species are fairly cold-hardy and don’t require much special attention to make it through the winter. Evergreen varieties tend to be more sensitive to the cold, so research the temperature requirements of any varieties you intend to grow and make sure that they’re suited to the winter temperatures of your local area. You should mulch around the base of your azalea in the autumn to protect its roots from frost. 

FAQ’s  

Is Azalea toxic?

All parts of the azalea plant are toxic to both animals and humans because they contain grayanotoxins. Depending on the amount consumed, ingestion can cause a range of unpleasant symptoms, from stinging sensations around the mouth to low blood pressure, nausea, hallucinations, seizures, or even death.

Do pollinators like azaleas?

Many pollinators are attracted to azalea because of their brightly coloured blooms, although, because of the toxins contained in the flowers, they can actually be very dangerous to beneficial insects. Although some bees are unharmed by the toxins, for other species of bee it can be fatal, so it’s best to avoid planting azalea in wildlife or conservation gardens to be on the safe side.

How long does an azalea live?

With the correct care and conditions, Azalea bushes can endure for many decades, even centuries. In fact, the oldest known azalea is in China and is thought to be over 260 years old! An azalea is definitely an investment for the future, delivering beautiful blooms year after year after year.

Just so long as you can provide acidic soil, you should have no trouble growing an azalea with abundant blooms. And with thousands of unique varieties, there’s bound to be an awesome azalea that’s the perfect fit for you and your garden. Once established, this relatively fuss-free flowering shrub will faithfully return each year to delight onlookers with its springtime displays for generations to come.