Azalea – Azalea – Garden plants – Characteristics azalea – grow azalea

Azalea is not a genus in itself, but is part of the rhododendron genus. This genus is divided into two groups: the rhododendrons, large evergreen or deciduous shrubs, and the azaleas, evergreen dwarf shrubs, with green leaves, or small and deciduous. Until a few years ago, they mistakenly thought that they were two distinct species, but, in reality, it is azaleas that rhododendrons are part of a single genre, that of the Rhododendron precisely, which in turn is part of the family of heathers.

They have an average size, reach the 40-90 cm of height; the thin stems, semi-woody, are densely ramified, and originate round or elongated shrubs; the leaves are oval, of dark green colour, rough and slightly leathery; in spring, before the leaves come out, they produce several trumpet-shaped flowers, united in small bunches, at the apex of the branches, of pink, red or white colour; there are many cultivars and hybrids, and in the last years on the market are present also azaleas lilac or bluish.

The evergreen varieties are slightly cold and are therefore grown as indoor plants; the deciduous or semi-evergreen varieties are grown in the garden.


Azalea cultivation

The azaleas belong to the genus Rhododendron. Botanists have unified the species in recent years, realizing that there are no substantial differences.

Some distinguish the two genera by counting the number of stamens or relying on the difference between deciduous or persistent plants.

Others, on the contrary, point out that the azaleas have more pointed leaves and with small hairs whilst, observing those of the rhododendrons, with a magnifying glass, we can notice small scales.

In this article we will deal with the general conditions of cultivation, which are suitable for both kinds, but we will have a particular interest in the cultivation of these plants in pots.

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Azalea temperatures

Temperature azalea Generally azaleas love to be cultivated in a temperate climate. They will certainly not be damaged if the temperature in our area ranges from -10°C to 20°C. However, it is possible to buy even more resistant varieties, the result of research and hybridization in recent years. If lower temperatures are reached in winter, it is better to withdraw the plant in a cold greenhouse or, if this is not possible, to place it next to a wall in the south that protects it at least from strong winds.

It can also help to put insulating material around the pot and cover the aerial part with a special sheet. In summer it is best to place it in the shade of large deciduous trees or conifers, always keeping the ambient humidity high, much more important than that of the ground. For plants in the ground is always worth the advice to choose well the exposure. The more we live in a warm climate, the more it will be essential to prefer a shady and cool area.

Soil azalea

Azalea The substrate is certainly the most important element for the successful cultivation of these plants. In fact, heathers need soil that tends to be acidic, with an optimal pH of around 5/5.5. Too high a pH inhibits the absorption of nutrients and is the most frequent cause of chlorosis, which occurs with the yellowing of the leaves.

These plants need a soil rich in organic substances, well drained and without water stagnation, and should not be planted too deep, as they have a very superficial root system. They can also be grown in pots, remembering the greater demand for watering the plants in pots compared to those placed in the ground. Azaleas are acidophilic plants. They therefore need at least a sub-acid soil (the ideal is pH 5, 5-6).

The ideal soil is therefore the one that can be found underneath the conifers. To cultivate them in a pot you can then recover some of this soil from our garden or buy some suitable ones. In any case, preparations with a high percentage of peat should be avoided. Rather, it is better to choose a generic soil and mix in needles, pine bark and possibly draining material (ideal is volcanic pumice or at most perlite).

In order to keep the soil fresh and to avoid as much as possible the change in pH, a good insulating layer can also be provided on the surface, always with the bark and the pine needles. The root system does not develop in depth and therefore they will need wider than tall pots. An excellent drainage layer of at least two centimetres must always be provided at the bottom. It can be composed of pumice or expanded clay Let’s avoid gravel that could release calcium carbonate.

Always ensure that the drainage holes are free. Whether in the ground or in a pot, it is ideal to place the azalea in a slightly raised position above ground level, creating a mountain. This will prevent water stagnation where the plant is most delicate, i.e. in the area of the collar. However, until the plant has stabilised, it will involve more frequent irrigation operations.

Azalea exposure

Azalea In areas with a mild climate, azaleas should be planted in a sunny place; in areas with hot summers, however, it is advisable to place azaleas in a semi-shaded or shady place. Garden varieties do not fear the cold, even in case of very cold temperatures. The shade is undoubtedly preferable. We can evaluate different exposures if we live in alpine or prealpine areas. Here we are particularly helped by lower temperatures, frequent rainfall and naturally higher atmospheric humidity.

This does not mean that some varieties, especially deciduous ones, are not particularly fond of exposure to the full sun and this will help them to bloom abundantly: the corollas, however, will last less. However, they are specific characteristics of the cultivar and to know this you can only experiment. If the plant is in a pot, it is certainly worth it (especially if we live in a cool area) to try various exposures before deciding on the final one.

Azalea watering

Annaffiature azalea From March to October, water the azaleas regularly, but avoid soaking the soil; during the winter months, water sparingly, only in case of prolonged periods of drought; the evergreen azaleas need to be watered throughout the year, keeping the soil slightly moist.

For a healthy and regular growth of the plant is very important fertilization. After the plant has taken root, it will be necessary to fertilize periodically with specific products for acidophilic plants; the yellowing of the leaves, due to chlorosis, is hindered by providing periodically a soil improver based on iron chelates. Azaleas do not like to have their roots constantly wet. This can cause rottenness and poor growth.

It is necessary to intervene more frequently after the repottings or after the planting, but let’s make sure that the substratum is always slightly humid, but absolutely without excesses.

It is much better to water abundantly once only, and then wait for the substrate to be completely dry than to distribute water constantly and without criteria.

If the days are particularly hot and dry it is very useful to vaporize the leaves several times and (if we keep the plant on a paved) wet the surrounding area so that the water evaporates gradually. It is excellent to place the plant on a saucer full of water and gravel, without it reaching the roots. It may also be useful to put other broad-leaved plants around which their transpiration helps to maintain a good environment for azaleas.

We remind you that, since these plants are generally calcifuges, it is better for irrigation and vaporization to use demineralized water (like the one for irons). Rainwater can also be collected and used if necessary.

Some tips

azalea To always have beautiful azaleas to envy the neighbor we give you some small tips. Always remove the flowers at the end of flowering by carefully removing the flower stalk: this will prevent the plant from spending energy for the generations of seeds. Fertilise at least twice a month with iron sequesteria: the latter will help the absorption of nutrients with a clear greening of the leaves.

Finally, remember that these plants suffer particularly from watering during the hottest hours of the day, so it is good to wet them in the early hours of the morning or at night.

Azalea fertilization

To obtain beautiful blooms, it is advisable to intervene with specific fertilizers for acidophilic plants. Both slow release and liquid granular fertilizers are suitable. An excellent opportunity, to be combined with the vaporisations, are also the foliar fertilizers. However, it is necessary to administer very light doses because these plants naturally live in rather poor soils and do not particularly like to be stimulated.

Let’s fertilize generally from February to mid-July, but let’s not go any further. Our intervention could stimulate the vegetative growth and the new branches, still herbaceous, could be irreparably damaged by the winter frost.

Azalea pruning

Potatura Especially for potted specimens it is necessary to intervene with periodic pruning of the azalea to stimulate its growth, maintain its shape and prevent it from becoming too large. The ideal thing to do is to intervene immediately after flowering. By intervening too late, in fact, you can interfere with the emission of the branches that will carry flowers the following year. It is a good idea to cut more of the outer branches and try to shed light on the inside of the plant.

Those that are crooked or damaged, on the other hand, can be eliminated at any time.

Leakage of leaves

Like we said, there are deciduous azaleas and evergreen azaleas. The former usually lose their leaves by the end of summer. What is certain is that they lose their leaves first if they live in a dry environment.

Evergreens also lose their leaves. They do so in autumn and spring, but these have already been replaced by others grown in summer and at the end of winter. If the leaves turn brown in the summer it is a sign that our azalea has a problem. Usually it is too much or too little irrigation, unsuitable soil or excessive fertilization.


fiori azalea Chlorosis of the leaves can be caused by various factors, but usually at the base there is too heavy a soil and an abundance of calcium carbonate. As always, it is ideal to avoid watering the plants with hard water and not to use concrete pots. To remedy this, iron sulphate must be mixed with the irrigation water. This lowers the pH of the soil and makes the iron soluble again. If this is not enough, chelated iron can be administered either by irrigation or by foliar fertilization.

In any case, it will be useful to intervene as soon as possible by flare the plant and replacing the substrate with a more suitable one and avoiding the repetition of errors.

Life of azaleas

These plants are very long-lived. If treated in the right way, they can live more than 100 years. That’s why they are also widely used for the production of bonsai.


Unfortunately, it is not possible to give a precise indication of their flowering period. There are many varieties, cultivars and hybrids and they can flower from the beginning of March to late October, also depending on the climate in which we live. The advice is, if we have specific needs, to contact specialized dealers who can direct us towards a specimen that meets our needs for size, flowering, strength and color of the buds.

How to treat florist azaleas

Much of the azaleas we have in our potted house come from buying from florists. They are considered excellent pot plants because they are quite easy to force and, in addition to having an excellent visual impact, can be available all year round. But what is really difficult is to make them survive and return to bloom in the following years.

First of all, it would be important to be able to identify it in order to understand whether or not it is a rustic specimen. As soon as you get home it is important to remove the paper that surrounds it and, if the ground is dry, irrigate it thoroughly. An excellent method is to place it in a bowl full of water and wait until there are no more air bubbles. At that point you can take it and let it drain for a long time. This should be done once a week.

In any case, the soil must not remain moist for more than two hours. It should then be placed in the coolest area of the house, possibly where there is a high ambient humidity. The bathroom could be a good solution as long as it is not too hot. In winter it can be moved to an unheated room. Generally even 5 or 6°C are not a problem. From spring to autumn it should be fertilized monthly with a product with a low nitrogen content and high phosphorus content.

This stimulates rooting and bud production. Instead, excessive vegetative growth of leaves and branches should be avoided. It is necessary to check the roots every 6 months extracting the bread from the ground: if we see that they are many and tangled on the bottom, we must intervene by cutting them. The plant should then be placed in a slightly larger pot than the previous one.

Variety of azaleas

The name azalea is rather generic and within this label, true fans of these acidophilic plants know all the major varieties. A first difference is made between apartment azaleas and garden azaleas. A further more precise difference can then be made between the different varieties and cultivars of azaleas.

Azalea mollis is a type of azalea that is highly appreciated for its intense colours ranging from yellow to red to pink and passing through all the shades of this colour. The mollis have large funnel-shaped flowers but do not give a particularly fragrant flowering. One of the most interesting aspects of azalea mollis and its flowers is the fact that this plant blooms when the leaves are not yet present and therefore the color effect is particularly intense.

Jinfo Mountain azaleas

azalee di Jinfo Mountain For gardening lovers and travelers, here is a place where azaleas are the corollary to a unique view and environment, so special as to be identified as a world heritage site by the “Aposos”;UNESCO .

We are in China and more precisely on Jinfo Mountain, or Jinfo Shan, a mountain of 2238 meters of altitude that represents the highest peak of the Dalou mountains in Chongqing district. This peak, which means “mountain of the golden Buddha”, in addition to offering incredibly beautiful views, is also an area where azaleas are widespread. Between April and May, when these plants bloom, the mountain fills with pink, white and red blotches, creating an incredible chromatic effect.

Azalea in winter

Azalea is a plant that tolerates the cold winter climate of most areas of our country, including the major cities of northern Italy and the Po Valley. On the mountains and in the coldest Alpine valleys, winter frost and especially late frosts can cause serious problems of survival to azaleas.

In these areas, therefore, it will be advisable to cover the azalea plants with a cloth during the coldest periods of the year.

In addition to this, we must remember to give a little to drink to the evergreen azaleas even in winter, obviously taking care to do so away from the less cold periods of winter to avoid damage to the plants due to frost. The evergreen plants in fact maintain a minimum of vegetative activity even during the winter and in the absence of rain, when the ground becomes too dry, there can be serious problems to the plants planted outdoors.

Azalee in the house

Azalee in casa The cultivation of azaleas in the home must take into account the factors that diversify the domestic environment from the external one, i.e. the difference in temperature, the difference in humidity and the difference in light.

In the apartment and in the house the temperature is more constant than outside and in winter it is certainly better suited to the vegetation of azaleas. However, you should be very careful not to expose the azaleas grown in the house to excessive changes in temperature or too cold currents.

Before bringing the azaleas to the outside, therefore, it must be verified that the sudden changes in temperature are not too accentuated to avoid dangerous frosts, as well as in choosing the position of the plants inside our house you must be careful not to store the azaleas in areas too exposed to cold currents or too close to doors and windows that lead to the outside and that are often opened to ventilate the premises.

Light is another very important aspect to take into account and in particular in this respect you should place the azalea plant in a place with sufficient lighting, therefore close to a light source such as a glass door or a window.

Finally, as far as humidity is concerned, in the house the climate tends to be always very dry and you must be very careful not to send the plant in conditions of water stress, controlling from time to time the humidity of the soil and possibly providing with watering.