How To Treat Azalea Leaves Turning Yellow

One aspect you never want to see is your Azaleas leaves turning yellow. Your bonsai tree is sending you a message that something’s wrong, and you need to work out what it is before you lose it. There are several reasons it could be happening, which we’ll show you in this detailed guide.

Azalea leaves turning yellow

Here are the topics We’ll cover:

Here are the topics We’ll cover:

Why are my Azalea Leaves Turning Yellow?

When you see your Azalea leaves turning yellow on your bonsai tree, don’t panic just yet. You might not have a lot to worry about, and most of the conditions you can fix quickly. You may need to wait a bit before you see the changes come into effect, so be patient.

Change of Season

What you may not know is that there are two types of Azaleas: evergreen and deciduous. For the latter, the leaves will turn yellow and drop when winter arrives, maybe even in spring. It’s a natural occurrence and there’s nothing you can do to change it.

For evergreen Azaleas, you shouldn’t see any change of leaf color, specifically to yellow. It should be green all year round, so you definitely have a problem. Should you be experiencing this issue, move on to one of the other reasons below.

Change of Location

Many bonsai trees hate moving from one region or climate to another. When they become used to an area, they settle in and use the conditions to grow. Sudden shifts with changes to lighting and humidity cause it to stress, which is when you may see the leaves becoming yellow and falling off.

Lack of Nitrogen

Your Azalea needs nitrogen to form strong, healthy green leaves. If the soil has low levels of this macronutrient, the leaves will turn yellow and die. It usually happens when the bonsai has been in the soil for more than a year and absorbed all the available nitrogen in it.

Another reason for the nitrogen deficiency is if you’re performing mulching with items that haven’t fully decomposed yet. It absorbs the nitrogen from the soil as part of the decomposing process, which leaves less available for your Azalea. It’s better to let the mulch decompose completely before applying it to the soil.

Alkaline Soil

The ingredient that makes your leaves look green is called chlorophyll. One of the nutrients needed in the formation of this element is iron. Chlorosis is the condition where there’s an iron deficiency in your bonsai, which is the cause of your Azalea leaves turning yellow.

So, what does this have to do with alkaline soil? Well, the high pH level lowers the Azalea’s ability to absorb iron from the soil. The same problem occurs when you use lime or chalky soil. It’s best to have a pH level lower than 6 if you want to see the leaves turn green again.

Insufficient Water

Azaleas can’t handle high temperature and drought-like conditions, and it makes them stress when there’s not enough water or humidity. When you hit the peak of summer, it’s best to bathe the soil in water once a week and then check when the soil dries out again for more watering.

Another reason water could be the cause of your Azalea leaves turning yellow is when it drains too quickly from the pot. The heat will dry the moisture quickly, which will leave your bonsai tree thirsty. If this happens, you need to find a way to retain the liquid.

Poor Drainage

Finally, you may have a situation where the soil doesn’t drain fast enough. It causes a condition known as root rot, which can also be why your Azalea leaves are turning yellow. It means your bonsai can’t absorb nutrients properly, and it may lead to damage to the trunk and branches.

Azalea leaves turning yellow

Symptoms of Iron Deficiency in Azalea Bonsais

We’ve already mentioned that iron deficiency happens in soil that’s too alkaline, and it will result in less chlorophyll being formed. While you can test for most of the conditions above when your Azalea leaves turn yellow, iron is slightly trickier to check.

Fortunately, your bonsai tree has other ways of showing you it needs iron. For instance, the leaves may curl upwards into a cup shape, as the nutrient also helps keep the leaves of your Azalea healthy. You may notice that foliage develops more slowly, and leaves and branches may start drying out and falling off.

How Do You Treat Yellow Leaves On Azaleas?

Now that you understand why your Azalea leaves are turning yellow, we’re going to show you how to improve the situation. As soon as you’ve identified what the cause may be, you can use one of these methods to fix it.

Supply Food Rich in Iron and Nitrogen

If the problem is that it’s lacking nutrients, you should invest in fertilizer that specifically caters to Azalea bonsais. They are formulated to add the correct doses of nitrogen and iron to the soil.

However, you shouldn’t blindly trust that it will do the job. Always check the ratios and percentages on the container to ensure that there’s more nitrogen and iron than other components.

Water More Regularly

When it’s the heart of summer, we recommending watering more than you usually do when the leaves turn yellow. Your Azalea will love the bath, especially if you spray the leaves to cool them down and add humidity. Always check the soil with your finger to see if it’s dry before you add more, as you don’t want to contribute to root rot.

The most common cause we have found for underwatering is when people use irrigation systems to water all their bonsais at the same time. Different species need various levels of water, and your Azalea may not be getting enough. It’s better to attend to each of your trees individually to ensure they get exactly what they require.

If you want to use irrigation systems for your bonsais, we recommend placing bonsai trees together with the same watering requirements. You can water these for longer periods than those species that don’t need as much of it. In this way, you prevent root rot from forming in the bonsais that drink slowly.

Provide Ample Drainage or Mulch

If the soil is draining the water too quickly or slowly, you have a solution for either issue. You can add drainage rocks at the bottom of the soil to promote the water draining quicker from the soil. The roots won’t sit in the liquid and you won’t have to worry about diseases.

Should you want a situation where you want to retain moisture instead, you can add mulch to the surface. It stops the heat and sunlight from cooking the substrate and evaporating the liquid that your Azalea bonsai wants so much.

Increase the Acidity Level

Adding more iron to the soil won’t help if the pH level is too high, as the roots won’t be able to absorb it properly. If you’re using mulch to retain moisture, you can use items that also increase iron levels. One example is pine bark, which is ideal for lowering the pH level.

There are also fertilizers you can use to help with the acidity levels, but we prefer a more organic approach. Feel free to crush some eggshells or add composted banana peels to the soil, as this also helps. You can also go for coffee grounds, but this may conflict with your plan to add nitrogen, as the two don’t work well together, especially for developing flowers.

Move It to More Light

Finally, we recommend you assess the light levels in the location where you’ve placed your Azalea bonsai. If there are low light conditions, it isn’t getting enough sunlight and the leaves will turn yellow. It’s best to leave them outdoors in spring and summer.

Remember, deciduous Azaleas will drop their leaves in winter. However, we understand you’ll want to bring your evergreen version indoors to protect it from frost. You can still provide it with morning sunlight by housing it near a window.

Azalea leaves turning yellow

Final Words

With Azalea leaves turning yellow, you need to take extra care to address any of the above issues. If the bonsai tree is too far gone, you won’t be able to save it, so you should address it early before it’s too late. We hope we’ve managed to help your solve the problem.

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Shaun has two passions in life that combine into an extravagant show on Bonsai Alchemist. The one is for writing and the second bonsais. He’s been writing fantasy and horror novels since 2000, while also creating online content since 2015. He’s involved with writing for films and games. Finally, he’s also the owner of a book publishing company.

He received his first bonsai as a gift in 2009 and has been growing several species in his quiet home in South Africa. He prefers propagating new life instead of buying bonsais at the store. His son and daughter share his love for nature, while his wife stares on at her introverted hermit husband.


Shaun M Jooste


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