Azalea (All Species)

Azalea 'Flandresse'


  1. Top Tips
  2. Location, Water, Humidity & Fertilisation
  3. Dormancy Period & Achieving Flowers
  4. Common Issues
  5. Origins, Temperature, Propagation, Repotting & Toxicity.

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Top Tips & Info

  • Care Difficulty - Moderate to Hard
  • Azalea like bright, indirect light away from excessively dark situations. Although an hour of direct sunlight in the early morning is accepted, be sure not to fall in the trap of sun-scorch and dehydration. 
  • Provide near-constant moist soil, allowing the soil's top third to dry out in between waters. Reduce irrigations slightly further in the height of winter. 
  • Supplement at monthly intervals all year round, using a houseplant-labelled fertiliser to ensure quality foliage and flower development. 
  • Repot every two years during the spring, using a 'Houseplant' labelled potting mix.
  • Keep an eye out for Spider Mites & Aphids that'll hide in the plant's cubbyholes and underneath the leaves.
  • Unfortunately, Azalea usually only last a few years due to the species' tendency to die shortly (a year or two) after flowering in domestic settings.

Location & Light - 🔸🔸

If you're a forgetful waterer, avoid direct sunlight costs - the combination of too little soil moisture and intense rays will quickly lead to a miserable plant. If, however, you can provide good soil moisture throughout the year, a splash of either morning or evening sun will significantly benefit the Azalea. Never situate this plant in a shady spot; if you're worried about its location being too dark, if a newspaper can be read while having your back towards the light source, you're good to go.

Location: Place this on a north, east or west-facing window for optimal photosynthesis. Never situate an Azalea in full sun, or a location that'll exceed the maximum temperature bracket of 25ºC (77ºF) - an example of this would be a south-facing windowsill or hot conservatory.

Water - 🔸🔸🔸

Azalea aren't a fan of having dry feet for too long. Once the top third of the soil has dried out, rehydrate by using the bottom-up method to reduce the chance of fungal diseases associated with excess moisture on the foliage - see image below. Submerge the bottom fifth of the pot in a saucer of water until thorough absorption, repeating this every five days all year round. Whilst the plant is in bloom, it's essential not to use cold water as this will quickly shock the roots, causing multiple issues down the line. Under-watering symptoms include rapid flower loss and dry, sunken leaves; these issues are usually due to either forgetfulness, too much sunlight or too much heat. Over-watering symptoms include rotting lower leaves, yellowing leaves, a loss of buds or flowers, and root rot. Allow the majority of the soil to dry out in between waters, preventing a pool of standing water from accumulating beneath the pot.

The best way to water your Azalea is by submerging the pot's bottom fifth in water every five days or so. Submersion is one of the best ways to promote reliable soil moisture to downplay the risk of dehydration - common with this group of plants. 

Humidity - 🔸🔸

Average room humidity is more than enough to occupy an Azalea, as too high humidity and poor air circulation will result in powdery mildew. Do not mist the flowers as this will cause botrytis petal blight that can spread quickly if not dealt with accordingly. Never situate this plant within three metres of an operating radiator as it will cook both the plant and the surrounding air moisture. 

Fertilisation - 🔸🔸

Use a fertiliser high in potassium to prolong its flowers during the festive period - an excellent example would be a Tomato Feed. Regular fertilisers, for instance, BabyBio or Miracle-Gro, will still do the job but will favour foliar growth instead. For the rest of the year, a standard fertiliser can be used to supplement the plant.

Dormancy Care & Annual Flowers

Trying to achieve a bloom isn't the hardest of tasks, with those who have a cooler room without artificial light at night being on the upper-hand. The following steps should be done at the start of autumn until the end of winter when the plant's growth starts to slow down. Always think of ukhouseplants' acronym of SHORT when it's time for flowers. 

They're better off staying pot bound for several reasons, including the prevention of root rot or transplant shock, and to put momentarily stress on the plant. Although this may sound harsh, a restriction of roots is the best way to obtain flowers, as it'll send out a spike in response to becoming under threat. As long as the plant is subsequently repotted tri-annually in the spring, no harm is done.

Sunlight & Location

Be sure to provide a bright location with little to no direct sunlight. Although the winter rays won't necessarily hurt the plant, you can easily fall in the trap of sun-scorch and severe dehydration.

For the specimen to fully become seasoned, avoid the use of artificial lighting or locations that boast temperatures higher than 18℃  (64℉).


Reduce waters so that about half of the soil becomes dry. It's essential to keep them on the drier side to life, as they'll think that hard times are ahead and therefore will need to pass its genes on to the next generation.

Occasional Feeds

While in bloom, use a Tomato fertiliser to provide monthly nourishment of potassium.

Reduce Everything

This one is to remind you that everything needs to be reduced - especially the temperature.


This is the most significant step; reduce the temperature down by around 5℃ compared to the summertime or place in a room that's around 15℃  (59℉). The drop in temperature should ideally last until the inflorescence finishes blooming, although it can still be transferred into the main house as long as it sits on a pebble tray. You'll be at a significant disadvantage if the ambient temperature is kept constant throughout the year, as Azalea will only respond with flowers in cooled environments. Never exceed the minimum temperature as it could lead to plant death or yellowed foliage at a bare minimum.

A developing Azalea bud that'll fully open within seven days, lasting up to fourteen days.

Common Issues with Azalea

Under-watering is the biggest issue when it comes to an Azalea. Typical signs of this include wilting, sunken leaves, rapid flower or bud drop and stunted growth. Not only will you have to be mindful of persistent droughts, think about which plant parts to keep dry. Its foliage must also remain dry at all times to prevent the development of diseases and blights. Those situated in direct sunlight or within four metres of a radiator are more likely to suffer from under-watering related issues.

Excessive periods of droughts will increase the likelihood of plant death, whereby it won't 'bounce back' shortly after wilting. 

Too much sunlight will lead to sun scorch, with typical signs including browning or crispy leaves, dry leaf-edges, sunken leaves or stunted growth. Although too little light will cause over-watering issues, too much sunlight will also be a detriment. Unfortunately, indoor Azalea cannot tolerate more than two hours of direct sunlight a day, unlike their outdoor counterparts. If yours has fallen short of this, reduce the amount of sunlight considerably and always be mindful of environmental shock (when two locations offer too different growing conditions). Remove some of the affected leaves and increase waters slightly. Only hydrate the plant using the bottom-up method.

As mentioned before, powdery mildew and botrytis are major threats among heavy foliage plants due to the compact nature that aids the spread of the diseases. Watering above the foliage will allow excess moisture to sit in the cubbyholes of the stem, enticing harmful bacteria to thrive. Remove the affected areas and improve the growing conditions by situating the plant in a brighter location with the use of the bottom-up method of irrigation.

Never situate an Azalea in more than two hours of direct sunlight or within four metres of an operating heat source, for instance, a radiator or fireplace. Due to the heightened temperature, the plant will soak up far more moisture than those situated in cooler locations, increasing the chance of droughts and inevitable death. This species cannot cope with persistent dry soil; you're skating on thin ice if an Azalea starts to wilt. 

Sudden flower loss can be caused by an array of different issues, including a change in location, too little hydration, too hot or cold temperatures or droughts and pests. Whilst the plant is in bloom, keep the soil evenly moist, to hydrate the thirsty work of producing flowers. Locations that are outside of the recommended temperature bracket, or have drastic fluctuations must also be kept off the cards, as Azaleas can be very sensitive to the ambient warmth that they're situated in. The final issue could be to do with pests. Although it's improbable that an infestation will cause a sudden change in health, have a quick inspection for WhiteflyAphids and Mealybugs

Pests could also be an issue, most notably being Whitefly and Mealybugs. Especially before purchasing, have a quick scan over the plant's foliage and flowers, inspecting its cubbyholes for those white critters. If your specimen has fallen foul of pests, click on the appropriate links to learn more about treatment, as well as observing their appearance.


Variegated specimens are continually on the rise in garden centres, due to their high demand.



There are over eighty species of 'Azalea', which is a sub-genus that falls in the family of Rhododendron. Some species, however, have been reclassified in Kalmia after several morphological studies. The sub-genus was first described back in the mid-nineteenth century by Jules Planchon, whereas the term, Azalea, was penned by Carl Linnaeus in the 1750s. Its name originates from Greek, meaning 'dry' that refers to the several species' tendency to thrive in well-draining soil. 

The Distribution of Azalea (synonymous of Kalmia).


10° - 25°C   (50° - 78°F)
H1c (Hardiness Zone 11) - Can be grown outdoors between late spring and summer throughout most of the UK while nighttime temperatures are above 8℃  (46℉).  If you decide to bring the plant outdoors, don't allow it to endure more than an hour of direct sunlight a day as it may result in sun-scorch. Regularly keep an eye out for pests, especially when re-introducing back indoors.

Azalea thrive in cooler locations and will generally flower better if a good dormancy is served in the spring when the temperature dips below 15°C  (59°F).


Up to 0.6m in height and 0.7m in width. The ultimate height will take between 4 - 6 years to achieve.

Pruning & Maintenance

Remove yellow or dying leaves, and plant debris to encourage better-growing conditions. While pruning, always use clean utensils or shears to reduce the chance of bacterial and fungal diseases. Never cut through yellowed tissue as this may cause further damage in the likes of diseases or bacterial infections. Remember to make clean incisions as too-damaged wounds may shock the plant, causing weakened growth and a decline in health.

It's quite difficult for amateurs to shape an Azalea, as it'll require a lot of effort over  eighteen months to promote a globular shape. Instead, allow the flowers to fully elapse (usually in the end of winter) before pruning the foliage back a third in time for spring.


Via Seed or Stem Cuttings.

Stem & Eye Cuttings (Moderate) - This method of propagation is troublesome without the aid of bottom-heat and a controlled environment. Choose the healthiest, most established stems that are wooded, yet still juvenile enough to bend slightly, being just thicker than a phone charger wire. Each cutting should only have a few leaves leaf, above 8cm of semi-wooded stem. Situate the cutting's lower half into moist 'Houseplant' compost; 'Blackleg' can occur when the bottom wound becomes infected, resulting in propagation failure - typically caused by water-logging or deep damage. Maintain bright light and evenly moist soil with the avoidance of direct sunlight or cold draughts. Wrap the pot (& foliage) in a transparent bag or within a miniature greenhouse, and provide bottom heat of temperatures above 18°C (54°F). Remove the bag and place into individual 7cm pots once the second new leaf emerges. Follow the same care routines, as mentioned in the article's top half. This method will take up to five months, so patience and the correct environment are paramount for success!


Indoor Azaleas will flower between autumn and winter if grown correctly with a good dormancy served in the spring and early summer months. Each individual flower will last up to two weeks, with the overall show lasting up to six weeks. Supplement the plant using a fertiliser high in potassium to prolong its flowers - Streptocarpus or Tomato feeds are an excellent choice.


Repot biannually in spring using a 'Houseplant' labelled potting mix and the next sized pot with adequate drainage. Azalea are far better potbound for several years due to the heightened risk of root rot and repotting-issues (like transplant shock), so only repot if you feel it's wholly necessary - restricted root growth will also increase the chance of blooms, too.

Hydrate the plant 24hrs before the tinkering with the roots to prevent the risk of transplant shock. For those situated in a darker location, introduce an extra amount of perlite and grit into the deeper portion of the pot to downplay over-watering risks. Click on this link for a detailed step-by-step guide on transplantation, or via this link to learn about repotting with root rot.

Book a 1-to-1 video call with Joe Bagley if you'd like a personal guide to repotting your houseplant. This will include recommending the right branded-compost and pot size, followed by a live video call whilst you transplant the specimen for step-by-step guidance and answer any further questions!

Pests & Diseases

Keep an eye out for whitefly, spider mites, thrips, aphids & mealybugs. Common diseases with Azaleas are root or crown rot, powdery mildew, leaf-spot disease, botrytis petal blight and powdery mildew. For more info on how to address any of these issues, hit this link - Identifying Common Houseplant Viruses & Diseases.


Azaleas are considered highly poisonous if consumed by pets and humans. If high quantities are eaten, it may result in vomiting, nausea and a loss of appetite.

Retail Locations

Some florists & Online Stores. Specimens are likely to be found in autumn at most garden centres. A small selection of Azaleas are sold during the spring and summer but generally won't last as long as those sold later in the year. It's not advised to bring outdoor specimens inside as this could lead to environmental shock or the introduction of foreign pests into the home.

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