Horticulture Magazine

Azalea Shrub Care & Growing Tips

tropical pink azalea up close

Azalea Overview

Official Plant NameTechnically now classified as ‘Rhododendron’
Common Name(s)Azalea
Plant TypeShrub (some are Houseplants)
Native AreaAsia, North America
Hardiness RatingVaries by type
ToxicityToxic to pets
FoliageEvergreen
FlowersBright blooms in Spring
When To SowMarch, April, May, September
Flowering MonthsMarch, April
When To PruneJune
Sunlight

Preferred
Full Sun or Partial Shade

Exposure
Sheltered

Size

Height
0.5 – 4M

Spread
0.5 – 4M

Bloom Time
May – June

Soil

Preferred
Loam, sand

Moisture
Moist but well drained

pH
Acidic

Among the most prized and celebrated of flowers, many would say that an Azalea in full bloom represents the Floral Ideal. Be the plant deciduous or evergreen, be the flower small or large, an Azalea is that Keatsian “thing of beauty.” With its vast array of varieties there’s an Azalea to project innocence and charm through sensuousness and sensuality. In sum, Azalea is the original ‘superflower.’

Azalea is a much-loved plant in the Deep South, many other American states, Japan, China, and the Koreas. In fact, the Azalea is an important and integral part of both the landscape and the culture in these very different geo-political regions. It is a shrub, deciduous or evergreen, that bears among the most diverse, attractive, and showiest flowers of all. 

Though Azaleas and Rhododendrons are distinct plants, they are very closely related and hybrids between the two have arisen or been developed. 

Each of Azalea and Rhododendron used to be a genus of its own under Carl Linnaeus’s classifications. However, professional Botanists and Taxonomists got up to their usual mischief, re-classifying and re-arranging the genera and their species and confusing us poor lay gardeners! But then, growers and gardeners themselves were also partly to blame because all too often they would not, and still do not, distinguish between the two plants and, instead, use the names ‘Azalea’ and ‘Rhododendron’ interchangeably, though horticulturalists were and are usually more disciplined. 

A long struggle to subsume Genus Azalea within those Rhododendrons was waged from 1834 to the early 1900s, when the resistance ended. A scattered insurrection continues.

So as it stands, Azaleas are subsumed within Genus Rhododendron, a member of Family Ericaceae or the Heather Family. These plants are well-known to be acidophilic. Azaleas are classified under two sub-genera, Pentanthera and Tsutsusi. The former sub-genus comprises of about 25 species that are deciduous; these are native to the southern U.S.A.; the latter sub-genus includes about 15 species that are evergreen, and these are native to a swath of East Asia. As for the hybrids and cultivars, there are untold thousands of them; as a result, many evergreen Azaleas are grown in the United States.

off-pink azalea blooms
Azaleas Can Project an Innocent Charm

Rather than lay out lengthy descriptions as to how to tell apart Azaleas and Rhododendrons, we provide a handy chart for quick lookup and differentiation. Factors are listed in descending order of decisive importance. We do not include blooming season as a factor because this varies and overlaps so much by variety, climate, and geographic location.


AzaleaRhododendron
Number of StamensUsually 5 but up to 1010 or more
FlowersUsually Solitary/TerminalAlmost Always in Trusses
Leaves – TextureSoft and SmoothLeathery or Scaly Underneath
Leaves – SizeSmaller and ThinnerBigger and Thicker
Flower ShapeTube-Funnel-ShapedBell-Like

There are other points of difference but those are more subjective and are also liable to overlap and to exceptions.

The reality is that Azaleas have been hybridised and cultivated for centuries in China and Japan, and the species are not of as much importance to gardeners as the pre-eminent groupings, series, and varieties, so from a practical point of view we focus on Azaleas as ornamental plant varieties and from an anthophilic perspective at that.

Although Azalea flowers are considered decorative and ornamental, these gorgeous things are themselves decorated and embellished. To begin with, no matter what hue the colour may be, it is almost always marvellous, from the palest flush of pink to the most saturated vermilion-red hue. The form and shape of the flowers is second to none with gently-curved but somewhat different tube-funnel shapes. As for those decorations and embellishments, we see curled petals, frilled petals, and ruffled petals; hose-in-hose and true double form; deep-hued flecks, contrasting streaks, and all manner of gradating, blotching, flaring, and sectoring. There’s an Azalea for an Audrey Hepburn and an Azalea for a Raquel Welch; an Azalea for a Leonora and an Azalea for a Carmen.

We live in an age of ‘superstars,’ ‘supermodels,’ ‘superlawyers,’ and such. There is such a thing as a ’superflower’ too— we present the Azalea.

red azalea flowers
Azaleas Can Project Sophistication and Seduction

Background and Origins

Azaleas are prized in Japan and have been so since hundreds of years ago when gardeners cultivated them for Imperial gardens. By now there are over 10,000 varieties worldwide. Before proceeding to our favourite varieties and taking in a representative ‘cross-section’ of the groupings and series, it would help to grasp the basic divergences among each of the two Azalea sub-genera. First, though, evergreen Azaleas typically have a mounding form and are compact whereas deciduous ones are usually taller with less branching. The evergreen forms bloom earlier in spring and do so profusely but the flowers are almost always unscented while the deciduous ones bloom in mid or late spring, with the flowers coming slower and less densely but typically having a sweet fragrance. 

red azalea blooming with trees in the background on Mt. Katsuragi in Japan
Azaleas in Lush Bloom in the Japanese Countryside

Evergreen Azaleas, for the most part descending from sub-genus Tsutsusi, are divided into four groupings.

Kurume Azaleas or Rhododendron ponticum are hybrids from Japanese species like R. kiusianum. They are dense, small plants, reaching just over a metre, and bloom in early spring, usually profusely. Many of the most desirable and popular evergreen Azaleas and RHS Award of Garden Merit recipients are Kurumes.

Southern Indian Azaleas or Rhododendron indica are also hybrids and also descend from Japanese species and have nothing to do with India. They are less dense and bigger, attaining heights of over 2 metres. They bloom in mid spring. They include exceptions like the ten-stamened ‘George Lindley Taber.’ This group is further sub-divided into cold-hardy Southern Indian Azaleas which can be grown as garden plants, and greenhouse Belgian Indian Azalea, which displaced the former as the Azalea of choice in England.

The third group of  ‘evergreen’ hybrids comprises of the Kaempferi Azaleas which are usually semi-evergreen. Like the Kurume Azaleas, these plants grow to about a metre but like the Southern Indian Azaleas they bloom in mid-to-late spring.

The fourth and final evergreen group of hybrids are Reblooming Azaleas. They too share attributes with both ‘major’ groups, being similar to the Kurumes in plant size but similar to the Southern Indian Azaleas in flowers and foliage. This group is very attractive for blooming twice, once in spring and then again, usually more profusely, in autumn. Encore is probably the most well-known and popular producer of such Azaleas and is on the way to becoming a grouping of its own.

Deciduous Azaleas which mainly descend from sub-genus Pentanthera species are usually divided into four groupings.

The oldest hybridisation of deciduous species are the ‘Ghent Azaleas,’ which date from the 1820s. These descend from crosses of American species with the sole European species. Seeds were collected in the wild in newly-independent U.S.A. in the 1780s by a botanist-cum-emissary sent by King Louis XVI. These plants have a somewhat rounded form with a height and spread of about 2.5 metres. They are generally disease-resistant, robust plants. Flowers are small and fragrant, and their double forms are renowned.

The Belgian-Dutch ‘Mollis Azaleas’ date from about 1840 and derive mainly from R. japonicum and not from R. molle, notwithstanding the (erroneous) nomenclator. They have a mounded form with a height of about 1.5 metres but a spread of nearly 2.5. They are more cold-hardy. Flowers are almost always unscented and the colours run through the orange-red spectrum.

The ‘Knap Hill Azaleas’ are a miscellany of hybrids that descend from both East Asian and American species as well as the sole European one. This group was bred by Waterer pere et fils from the 1850s onward. Varieties usually grow to about 1.5 metres but some attain heights of 2.5 metres. Spreads are typically from 2 to 3 metres. Flowers are distinctly larger and often have saturated hues in a wider spectrum from yellow through crimson, and include whites and pinks.

Finally, we have the ‘Exbury Strain’ of the ‘Knap Hills’ or the ‘Exbury Azalea’ Group that was cultivated in the 1920s, mostly deriving from the Knap Hills. These reach heights of 1 to 1.5 metre and are cold-hardy varieties. Flowers are large and have particularly deep and rich hues in the yellow to red spectrum. Seeds and flowers of this strain were exported to the United States, and now the Exburys are considered the most important grouping of deciduous Azaleas in American floriculture.

It is to be noted that the above horticultural classification is an ‘Atlanticist’ one. Japanese, Chinese, and Korean horticulturalists and their respective floral trades have their own classification and groupings for Azalea cultivars. 

Cote d'Azur harbour in the French Riviera
An Azalea Bush Adorns a French Riviera Resort Area

Varieties

Among the untold many thousands of varieties of Azaleas, we present a representative selection from the various groups, several of the most popular ones, and our favourites. Hollywood types would call most of these “Boffo at the box office.”

R. luteum or Common Yellow Azalea (Pentanthera) Attains a height of 2 to 3 metres and a spread of up to 2 metres. This is a Caucasus-region species naturalised in the U.K. Classic funnel-shaped flowers are small at about 4.5 centimetres and are a lovely buttery yellow and display long, prominent stamens. Very fragrant. RHS’s Award of Garden Merit. 

yellow honeysuckle azalea up close
R. luteum or Common Yellow Azalea

R. quinquefolium or ‘Cork Azalea’ (Japanese Deciduous) A Japanese species that is grown as a shrub, this species can grow to be a tree up to 7 metres tall. It is also unusual both in its foliage and its flower. The leaves, of a normal size and colour, display a purplish rim. The small 3- to 4-centimetre flowers are unusual in being pendent and bell-like. They have smooth, pure white petals with faint green spots on the upper three petals. They bloom in late April and May.

R. schlippenbachii or ‘Royal Azalea’ (Deciduous) This is a species native to Korea and the Russian Far East. Commonly grown to 1 to 2 metres, this variety can reach an ultimate height of 5 metres. It is very cold-hardy. The foliage is of particular note as the leaves are red-bronze when they emerge and in the autumn present a stunning show in yellows, oranges, and reds. The marvellous flowers are unusually open, are about 6 centimetres, and have smooth petals. The gentle fragrance perfectly matches the gentle hue of a translucent pale pink.

pink royal azalea on a mountaintop in Hwangmaesan, South Korea
Royal Azalea Growing in the Wild in South Korea

R. viscosum or ’Swamp Azalea’ (Pentanthera) This bushy plant is a species native to Eastern and South-Eastern United States. It usually grows to a height of about 2 metres and spread of about 1.5. It is very cold-hardy. The foliage has autumn interest, presenting shades of yellow, orange and purple. The small, tubular-funnel flowers are only 2 to 2.5 centimetres across and have narrow petals whose colour varies; they can be pure white, white with pink flecks and streaks, or some tone of pink. It is a profuse bloomer. Flowers have a spicy, delightful fragrance. RHS’s Award of Garden Merit.

pink Rhododendron viscosum in focus
Swamp Azaleas (R. viscosum) of a Rich Pink Colour

‘Cecile’ (Knap Hill)  The plant has a bushy habit and reaches about 2 metres in height and spread. The flowers are large at 8 to 10 centimetres. These have beautiful, gently-ruffled petals of a soothing pink shade, often gently gradated, with a reddish throat and yellow-orange flare on the dorsal petal. Flowers bloom in May through June. RHS’s Award of Garden Merit. Compare with ‘Berry Rose.’

Gibraltar (Exbury)  The plant reaches a height of 1.5 to 2 metres and spread of 1 to 1.5. The petals with their curls and frills impart a pleasingly ruffled appearance to the flowers. The colour is rich and intense, from a flame orange to proper vermilion, often with a yellow tinge. Medium-sized, about 6-centimetre flowers are fragrant. They bloom in May. RHS’s Award of Garden Merit. 

orange Rhododendron x hybrida flowers
Flame Orange with Curls and Frills – that’s ‘Gibraltar’

‘Hino-crimson’ (Kurume) This semi-dwarf attains a height and spread of about one metre. Foliage has some winter interest as it becomes reddish. Small, 4.5-centimetre single form flowers with smooth, flattish petals bloom in May. They are a solid colour; an intense, thrilling hue of pinkish-red. RHS’s Award of Garden Merit. 

Rhododendron x hybrida in a devon garden
A ‘Hino-crimson’ Bush in England Covered with Blooms

‘Purple Splendor’ (American Cultivar). Usually grows to 1 to 2 metres but can attain a height of 3 metres. It has a bushy and spreading habit. It is quite cold-hardy. Flowers are both large at about 8 centimetres and also bloom profusely in May. Petals are smooth. The colour is a rich shade of purple with a dark or red throat, and a flash with freckes on the dorsal petal. (Note: ‘Purple Splendour’ with a ‘u’ in Splendour is a Rhodie.)

pink Azalea japonica
Picture Perfect ‘Purple Splendor’ Azaleas

R. occidentale (A) or ‘Western Azalea’ (Pentanthera). Though its 10-year height and spread is about 2 metres, this species can grow to several metres. Fully open, the funnel-shaped flowers present a star-like appearance. They are pure white, or white with pink streaks and tinges and yellow flares, or some pastel tone. The flowers are very special, being large at 10 centimetres, sweetly fragrant, and blooming in late spring and early summer – June and July. RHS’s Award of Garden Merit.

Western Azaleas Rhododendron flowers with pink and yellow tinges
If it’s White with Pink Tinges and a Yellow Flare, it Must be ‘Western Azalea’

‘Delicatissimum’ (Occidentale). This variety has a compact, bushy habit and reaches a height and spread of 1 to 1.5 metre. Foliage provides some autumn interest. Trumpet-shaped flowers present a ‘delicate’ appearance, and are pale cream with a pale pink flush, a pink streak or sector, and a yellow flare. They are fragrant and bloom through June. RHS’s Award of Garden Merit. 

“Mother’s Day” (Kurume). A dwarf with a compact, mounding form of about 0.6 metres high and up to 1 metre wide. The leaves take on a bronzed tone in winter. The medium-sized flowers are about 6 centimetres and are hose-in-hose or double. They are a solid colour; a brilliant Lipstick Red. They bloom in May. RHS’s Award of Garden Merit.

‘Fruit Salad’ (Unknown deciduous). Plant reaches 1.2 to 1.5 metres. The smallish flowers are about 5 centimetres. They are funnel-shaped and present a star-like face. The petals are a vivid pink with streaks of deep pink and red. The dorsal petal is a rich orange, with adjacent petals displaying light orange flashes. Scented flower blooms in late June.

‘Elsie Lee’ (USA/Exbury) A semi-dwarf variety that attains a height and spread of about 0.8 metres. Semi-double flowers with delightful, richly ruffled petals of a pale yet bright lilac-purple hue. Medium-sized, about 6-centimetre flowers bloom in profusion in late May. RHS’s Award of Garden Merit.

‘Schneeperle’ (USA/Exbury) Dwarf variety of only about 0.35 metres with a spread of 0.5 metres having a creeping, clumping form. The flowers are small at about 4 centimetres and are in double form. Like a bridal veil they are snowy white but are embellished with a greenish-yellow-tinged throat. The petals have wavy edges. Flowers bloom in May.

white Japanese Azalea 'Schneeperle' shrub in focus
‘Schneeperle’ is Snowy White with a Greenish-Yellow-Tinged Throat

George L. Taber Southern Indica (Southern Indian). Grows to just over 2 metres tall and just under 2 metres spread. It is very heat tolerant. The flowers have a classic funnel shape and are large at 7 to 8 centimetres. The smooth petals are a pale orchid hue with an intense rose-mauve flare and flecks on the dorsal petal. Flowers bloom in profusion in mid- and late-spring.

Pink evergreen azalea flowers with green foliage
This George L. Taber Bloom is a Textbook Specimen

‘Addy Wery’ (EA) (Kurume). This compact plant reaches a height of up to 1.2 metres. Bears small trumpet-shaped flowers of 4 to 4.5 centimetres. They are a deep, rich vermilion to red; almost a solid colour bar slight gradation from the centre. Blooms profusely in late April through early May. RHS’s Award of Garden Merit. 

‘Iro Hayama’ (Kurume)  This semi-dwarf variety has a mounding form and reaches a height and spread of about 1 metre. It bears small, 4-centimetre trumpet-shaped flowers. The smooth petals are white gently gradating to a pale lavender or pale mauve. Flowers present an elegant, delicate appearance. Blooms profusely in May. RHS’s Award of Garden Merit.

‘Panda’ (Southern Indian / Kaempferi) is neither tubby nor black-and-white; rather, it bears the most delicate, indeed fragile-seeming, of Azalea flowers. This plant is a dwarf with a spreading habit that grows to only 30 to 40 centimetres. The small flowers are only about 3 centimetres. Petals are in an unusual imbricate form and are snow-white, appearing wispy or filmy, with the golden yellow of the anthers providing a strong contrast. It bears a profusion of flowers in May. RHS’s Award of Garden Merit.

white azaleas with green leaves
The Strangely-Named ‘Panda’ is a Wispy and Filmy Tiny Thing

The Encore Series. Encore is a patented brand of re-blooming Azaleas that were cultivated in Lousiana as recently as the 1980s. They produce flowers, sometimes abundantly, from spring clear into autumn, or produce blooms once in spring and again, often more profusely, in autumn. They are relatively heat-tolerant. Five semi-dwarf varieties are listed underneath.

Autumn Bonfire ‘Robleza’ (Encore). Grows to about 1 metre tall and wide. The single and semi-double flowers are medium-sized at 6 to 6.5 centimetres. They are a solid colour through and through, this being deep, pure red; perhaps the richest and most intense red of all Azalea varieties. 

Autumn Chiffon ‘Robled’ (Encore). Grows to about 0.8 metre tall with nearly a 1 metre spread. The single flowers are medium-sized at about 7 centimetres and have wavy petals. The colour is a pale pink flush with a freckled flash of scarlet on one petal.

Autumn Starlite ‘Roblem’ (Encore). Grows to about 1 metre with a similar spread. The single flowers are about 7.5 centimetres. The corolla is unusual in being imbricate. The petals are white with soft candy pink streaks and freckles. 

Autumn Lilac ‘Robles’ (Encore). Grows to about 0.8 metre tall with nearly a 1 metre spread. The single flowers are about 5 centimetres. The wavy petals are a rich lilac hue with the dorsal petal liberally flecked with purple.

Autumn Starburst ‘Robleze’ (Encore). Grows to about 0.8 metre tall with nearly a 1 metre spread. The single and semi-double flowers are about 6 centimetres. Their shape is unusual as blooms are sometimes rather salver-shaped. The petals are of a pale salmon ground with thick coral-red blotches through the centre of each petal, fading near the edge.

multicoloured blooms of azalea shrubs in a garden
A Stand of Azalea Bushes Covered in Multicoloured Blooms

Habitat & Growing Conditions

As seen in section Background and Origins, Azaleas are very wide-ranging genera of plants with different characteristics. As hybridisation and cultivation have proceeded, newer and newer Azalea varieties combine traits from different parental or genetic lines. One might say that the eight sub-groupings are suited to varying habitats and growing conditions to some degree. Therefore, the information in this section and also the following ones should be seen as an ‘averaging’ of sorts; as for the guidelines, they are generally considered best practice. In some cases, specific information and guidelines are also presented.

In sunny regions a majority of Azalea species set up shop under and alongside larger trees where they can enjoy sun in the morning and avoid it in the afternoon. These plants also like filtered sun and dappled sunlight through tall trees. 

azalea bushes growing under oak trees with a lake in the foreground
Azalea Bushes Growing Underneath Live Oaks in South Carolina

Azaleas grow in quite a range of habitats. Some species grow in cool, dry regions on mountainsides in China and Japan. Large swaths of Japan’s Mount Katsuragi and Mount Tokusenjo, to name just two, get covered with Azaleas every spring. Other species grow in warm and moist regions. For example, Swamp Azalea and ‘Mountain Azalea’ – surely a misnomer! – grow in and along the swamps and waterways of Lousiana, Florida, and other South-Eastern States.

Pink royal azalea blossoms on Hwangmaesan Mountain
Azaleas in Bloom on a High Hill in South Korea

The USDA Hardiness Zones of the various Azalea varieties ranges from down to 3 up to to 11. 

The majority of the popular Kurume varieties have a USDA Hardiness Zone of 5 to 8. Most Exbury varieties have exactly the same USDA Hardiness Zone and some are cold-hardy down to Zone 4. In contrast, Belgian Indian varieties are not cold-hardy at all. ‘Freckles’ has a USDA Hardiness Zone of 8 to 10, and ‘California Beauty’ only 9 to 10.

A little less cold-hardy than the Kurumes and Exburies but a little more heat-tolerant are Encore dwarf varieties whose USDA Hardiness Zone is 6 to 10. Southern Indian Azaleas’ USDA Hardiness Zone is not too different at 7 to 10.

Compare the wide range of very cold-hardy and very heat-tolerant Swamp Azalea’s USDA Hardiness Zone of 4 to 9 with that of Royal Azalea at ‘only’ 5 to 8.

Where to Plant Azaleas

As an exceptionally diverse set of plants, Azaleas can be used for nearly every single home, garden, and landscaping purpose from an accent in a rock garden and a single plant in a decorative container to wide boundary hedges and large landscaping bushes. An azalea that bears a good-sized multi-hued flower can be a superlative single specimen plant; other Azaleas can be just as terrific for mass plantings.

A particular Azalea may be selected (or rejected) for a specific purpose as suggested by the characteristics of that variety. Besides the Hardiness Zone, factors that you need to take into consideration include:–

  • Rate of growth
  • Ultimate size of Plant
  • Habit
  • Evergreen/Deciduous
  • Size of flowers
  • Fragrance/scent
  • Colour and patterning of the flower
a Japanese garden park
An Azalea Bush is One Element in a Japanese Garden

Say you want to make a boundary hedge using Azaleas (a long-term project). You would look for evergreens that grow fast, attain good heights and widths, and have a bushy, dense habit. As these are incompatible attributes you would really need to search high and low! In any event, you might reject all deciduous varieties. Evergreen candidates include ‘George Lindley Taber,’ ‘Purple Splendor,’ ’Snow White’ and ‘Kirin.’

At the other extreme, say you want to put a few potted Azaleas on your deck’s parapet. You would probably choose varieties for large flower size, eye-catching patterns with flares and streaks, and fragrance. You would reject all varieties with small or plain flowers. Good choices are ‘Swamp Azalea,’ ‘Western Azalea,’ “Autumn Starburst ‘Robleze’,” and “Autumn Starlite ‘Roblem’.”

Or perhaps you want to grow some different Azaleas in a bed. You could choose a mix of varieties, planting evergreen ones in the front and deciduous ones in the rear. Of particular importance would be the habit, as neat ‘self-maintaining’ mounding forms would be easy to maintain. And you would choose varieties for a harmonious mix such that the blooms would be ‘evenly matched.’ You could choose plants so that they start blooming together or bloom at intervals all through the season. A good selection for ’synchronised’ blooming would be ‘Panda,’ ‘Iro Hayama,’ “Mother’s Day,” and ‘Geisha Orange’.

On the other hand, you may opt for a concentration of the same hue but presented by rather different floral forms. To do a set in, for example, solid red, you could opt for ‘Maruschka,’ ‘Johanna,’ “Denny’s Scarlet,” and “Autumn Bonfire ‘Robleza’.”

Feeding, Care & Growing Tips

In general, all Azaleas need well-drained soils. A sand- and humus-based loam with little clay or silt would work very well for all Azaleas. Adding some peat moss would be beneficial. These plants will not flourish in heavy clay soils.

All Azaleas thrive in acidic soils, ranging from pH Slightly Acidic to Moderately Acidic. Depending on the variety, the recommended and optimum pH may be closer to 4.5 or to 6.5. With most any Azalea you can’t go wrong with soil pH from 5.0 to 6.0.

In sunny or warm regions in the summer, the soil should not be allowed to dry out; it should be kept moist. Mature Azaleas of most varieties are fairly drought-tolerant but if they go for a significant period without water, they will not bloom profusely or may not flower at all. Prolonged drought will cause them to shed their leaves and wilt. Though you may read that Azaleas are ‘drought-tolerant’ be aware that they are not properly or strictly drought-tolerant plants; after all, they are shallow-rooted.

Azalea varieties that are just barely cold-hardy to your region should be mulched upto soil level before the onset of winter.

Though Azaleas are considered ‘shade-loving plants,’ in cool and cloudy regions, like much of the United Kingdom, Azaleas can be grown in full sun. In warmer, sunnier regions Azaleas are best placed in locations where they get shade from the strong afternoon sun. However, they must get sun in at least the morning or late afternoon. 

In the United Kingdom, full sun is preferable for Kurume and Mollis Azaleas. In most geographic regions dappled sunlight filtering through tall trees is a very good option for most Azaleas.

In any region, white and light-coloured Azaleas should be protected from full sun or the afternoon sun.

Azaleas do not require fertilizing; indeed, there is such a thing as ‘over-fertilizing’ an Azalea. However, you can ‘feed’ Azaleas with a little ericaceous compost shortly after the end of flowering season or in July. Rich, organic humus is another option.

red azalea meadows in Mt. Katsuragi, Gose City, Nara Prefecture, Japan
These Blossoming Azaleas were Probably Never Fertilised!

When transplanting Azaleas take care that the top of the root ball is not below the soil – at all. Azaleas are shallow-rooting plants with evergreen varieties particularly so, and planting any Azalea even a little too deep in the soil can actually cause the plant to die. Indeed, plant an Azalea so that the top of the root ball is 2 to 3 centimetres above the surface of the soil.

In general, young Azaleas are ‘medium-care’ plants and established Azaleas are low-care plants.

Pruning Azaleas

You may deadhead Azaleas for three reasons: encouraging new blooms, for aesthetics, and if you wish to avoid self-seeding. Of course, if you would like to see new and unexpected Azalea varieties sprouting up in your garden, allow some withered blooms to go to seed.

In general, all Azaleas – all groupings – need no more than light pruning and trimming. For the most part they have ‘neat’ habits and form well-branched plants or bushes. Severe pruning – unless necessitated by some unavoidable reason such as pest infestation – will probably negatively affect the aesthetics and growth habit of the plant.

By all means trim overgrown areas, or straggly or stray branching, doing so judiciously to the extent of one-third to one-half of the length of the branch. Some deciduous varieties do require such pruning albeit infrequently.

Rhododendron and azalea bushes in a summer garden
None to Light Pruning for these Azaleas and Rhodies

The best time to prune an Azalea plant is right after its flowering season is over and the blooms have shrivelled up. Azaleas start to develop buds in about two months from the end of flowering season for the following season’s flowers so pruning Azaleas at or after this time would cause a reduction in the flowers you see the following year.

If you have grown an Azalea hedge or bush, you may wish to trim it as you would any other hedge or bush using hedge trimmers but Azaleas are not amenable to such trimming or shaping. If this is attempted, flowering will be negatively impacted and the least-desired outcome will be effected as subsequent plant growth will be unpredictable and unaesthetic. An Azalea hedge will need to be pruned and trimmed as would a plant, that is, by picking and choosing branches, and then either very selectively pruning them or cutting them back by no more than half their respective lengths. 

Azaleas are Poisonous

Azalea is a cat-, dog-, and child-unfriendly plant. The flowers as well as other parts of the plant are toxic. Though one little nibble is unlikely to cause anything more than a burning or stinging sensation in the mouth and gullet, salivation, or such, ingesting even a small quantity is poisonous and the threat to health and life should not be discounted.

The toxic compounds found in Azaleas are andromedotoxin and other grayanotoxins. These chemicals, among other ill effects, interfere with or block the functioning of involuntary muscle fibres such as those found in the heart and gastro-intestinal tract.

Initial symptoms of poisoning include salivation, weakness, lethargy, diarrhoea, and vomiting. Severe abdominal pain, loss of muscle tone, partial paralysis, and cardiac arrhythmia may also occur.

Children or pets who have ingested even a small quantity of Azalea plant should immediately be taken to an appropriate clinic for emergency medical treatment.

Pink azalea flowers
Could these Attractive Blossoms be Poisonous?

Honey made by bees from Azalea nectar is also toxic. It came to be known as ‘Mad Honey’ because of the symptoms exhibited by persons who had eaten it. Apart from depressed vital signs, the affected person often suffers from hallucinations and convulsions, hence the name.

In rural areas and the countryside, Azaleas pose a threat to livestock. Horses, cattle, sheep, and goats, are far more likely than cats and dogs to eat Azaleas, not just take a nibble or two. As a result, Azalea poisoning is often very severe in livestock.

Midsummer scenery of Hehuan Mountain
Livestock Should be Kept Away from this Stand of Azaleas on a Taiwan Mountain

Common Diseases and Problems

Though Azaleas are healthy plants in general and are not very susceptible to pests and diseases, they can be affected by a large number of pests and diseases.

The more common pest infestations include bark scale and other scale insects, caterpillars, and Pieris lacebugs (not to be confused with American lace bug species). The less common pest attacks come from aphids, vine weevil, and stunt nematodes.

The more common diseases to affect Azaleas are powdery mildew and rhododendron petal blight. The less common ones are silver leaf, azalea gall, and rhododendron bud blast.

If you observe any scale infestation, prepare a mild solution of soap and horticultural oil, and spray affected areas at a high jet setting to wipe out the pests. A more time-consuming but safer and more thorough method would be to dip a scrub sponge in the solution, and at one and the same time apply the solution to the plant while firmy rubbing away the insects. You could also prepare a one-percent solution of Orthene and spray it once a fortnight until there is no sign of scale.

For Pieris lacebugs you can use the same spray-jet method but use Neem Oil, Vitax, Bug Clear and other horticultural oils with which to make the mild solution. Ladybugs, which are natural predators of lacebugs, can be released on the affected plants. For a serious and persistent infestation, Sevin’s chemical products should be used. 

To combat caterpillar infestations the go-to natural remedy is Bacillus thuringiensis which are bacteria that are fatal to caterpillars. This is the main active ingredient in products like Bonide Thuricide or Dipel Pro which can be sprayed on the plants. To get rid of some caterpillars and repel the pests, put one teaspoon of vinegar and two of garlic powder in one litre of non-alkaline water, mix well, and spray on the plant.

If Powdery Mildew is caught early, it can be brought under control by severely cutting off all affected parts and destroying them. To avoid recurrence of the disease the plant should not be closed in by other shrubbery; it should enjoy free flow of fresh air and ample sunlight. 

Petal blight is very hard to control once it has attacked the plant. All affected parts of the plant and nearby areas need to be cut off and removed, as does the soil underneath and close by. If you live in a location where petal blight is known to occur, consider spraying your Azaleas with a fungicide that has tebuconazole and trifloxystrobin. Start spraying when the first buds just begin to show colour, and continue spraying fortnightly but if you are having wet weather then spray weekly. Do so until the flowering season is over.

An Azalea plant will be more resistant to pests and diseases if it is grown and kept in (close to) optimal conditions, as outlined in earlier sections, and if negative factors are reduced or eliminated. Such factors pertain to soil type, soil pH, temperature levels, sun-shade mix, root level, soil moisture, and drought. More than most plants, a happy Azalea is a healthy Azalea.

blossoming light pink azalea
Healthy Plants will Bear Lovely Flowers Like these

Where to Get Azaleas

It is easy to find popular Azalea varieties in pots and containers in just about every nursery and garden centre as well as online. In addition, many nurseries specialising in Azaleas sell lesser-known and uncommon varieties, including species, through their online stores.

You can ‘get’ Azaleas yourself by way of cuttings or layering. Both methods give good results with Azaleas though the ease or difficulty does vary by variety. The best period to take cuttings is August, and the best for layering is October.

Azalea seeds are widely available. Azaleas cultivars seldom come true from seed though species do. Keep in mind, though, that depending on the variety an Azalea takes from two to four years from germination to start flowering.

Sow Azalea seeds outdoors in mid- to late-spring. When it is time to transplant the young plant, make sure you know the variety’s ultimate spread and transplant accordingly as varieties’ spreads vary by multiples and transplanting a mature plant is not a good idea. 

If you have the equipment and know-how to sow Azalea seeds indoors, then do so in November. That way you will take a year off the typical number of years it would take for that variety to start blooming.

When growing Azaleas from seed or by cutting, or if you have acquired a very young plant, water it with distilled water to be on the safe side. Otherwise test your tap water for its pH. Do not water very young Azaleas with alkaline water.

woman caring for plants in a greenhouse
A Young Woman Inspecting an Azalea Plant in a Nursery

Fun Facts About Azaleas

Azaleas are a part and parcel of the culture, rituals, and lifestyle of a significant proportion of the populace of the Deep South, the Koreas, and Japan, and to some extent also some parts of China.

• Starting with beverages, Azalea Springs is a Napa Valley vineyard whose Merlot is reckoned to be particularly good.

• Then there is the Azalea Cocktail, a vodka-based mixed drink that is a must-have at the Masters in Augusta, Georgia.

• Topping both is Chungcheong Province in South Korea because a ‘wine’ is actually made from Azalea petals in that region. This ‘wine,’ called ‘Dugyeonju,’ is less like a wine and more like a dessert liqueur.

• Staying in South Korea and transitioning to food, we have ‘Hwajeon’ which is a pan-fried cake made of rice and wild-growing mountain Azalea petals.

[Be aware that Azaleas are poisonous and are not meant to be ingested. In Korea, only the petals and no other part of only one early-blooming species are used in the preparation of liqueur and rice-cakes; only that one part of only that sole species is known to be non-toxic.]
sweet rice cakes with flower petals
Would you Like to Sample a ‘Korean-Azalean’ Hwajeon?

• Both South Korea and Japan have many ‘Azalea Festivals’ (sic) and these are so numerous that one would be hard-pressed to list them all.

• ‘Azalea Festivals’ are also part of the fabric of the American South, with those of Georgia, Florida, and North Carolina being the biggest and most well known.

• Georgia has had a State Flower, the Cherokee Rose, since 1916 but in the 1970s Georgians also wanted the Azalea to be associated with their state. Conveniently, in 1979 the Azalea was proclaimed Georgia’s ‘State Wildflower.’

• As we’re back in Georgia, the Augusta National’s holes are named after trees and plants. Number 13, a Par 5, is ‘The Azalea.’ How can that be unlucky?!

• It is not at all surprising that the United States, China, North Korea, South Korea, and Japan have issued Azalea postage stamps, but, more interestingly, so have Belgium, Austria, Poland, and Iceland.

stamp printed in Japan shows Azalea flower
A 2002 Postage Stamp Issued by Japan showing the Azalea

• Mobile, Alabama is well known for its Azalea Trail and probably even better known for its Azalea Trail Maids; genteel and polished Southern girls who serve as ambassadors for Mobile in particular and Alabama in general, and appear at national events throughout the country. 

• Duke Ellington and Louis Armstrong recorded (only) two studio albums together. One of the most unusual and one of the finest tracks (and recognised as such) was composed by the Duke and caressingly sung by Satchmo. That ballad is ‘Azalea.’

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