Why Are My Azalea Leaves Turning Black? (And How to Fix It)


Indoor potted azalea leaves turning turning black.

Azaleas bring color and beauty to any home. It will break your heart if you find your beautiful azalea plant leaves turning black.

To revive your azalea you need to find out the causes and then take action on the basis of that. Keep reading to find out the causes and how to fix them.

Azaleas require very specific conditions. If any of these are lacking or incorrect, your azalea will quickly begin to struggle. The most common reasons for azalea leaves turning black are over and underwatering, soil drainage, over-fertilizing.

This article will discuss each of these and the best ways to ensure your azalea’s leaves stay healthy and green. Now, let’s dive into the details.

Causes of azalea leaf turning black

It can often feel overwhelming when your plant starts to look sick, but all of these problems have simple solutions.

By ensuring that your plant has everything it needs to be healthy, it will be back to its beautiful self in no time.

WATERING

One of the biggest mistakes when caring for indoor plants is incorrect watering. Every plant has specific needs regarding how much water they need. 

Both watering too often and too little can adversely affect plants. This is one of the most common reasons azalea leaves begin to turn black. Azaleas can be temperamental plants.

How Much to Water

Azaleas prefer moist soil, and they hate being left in standing water for long periods. To avoid this, it is important to check your azalea’s soil regularly. 

If the soil feels dry, it is time to water it. However, if the soil is already moist, wait until it has dried out a little. Do not let the soil completely dry out. 

The amount of water your plant will need will vary throughout the year. Plants will require less watering during colder, winter months, and more during hot weather. If you are unsure, regularly check the soil.

While you can pour water into the pot, azaleas appreciate being submerged regularly as it allows the soil to absorb more moisture. 

To do this, submerge the entire pot in a large container of water which is at room temperature. Small bubbles will be visible rising to the top of the pot. 

Once the bubbles have stopped rising, remove the plant and allow it to drain until no water runs from the bottom. 

It is important to remove the pot once these bubbles have stopped as forgetting to do so will cause the roots to begin to rot.

Using the Right Type of Water

Azaleas are also very temperamental to the type of water you use. They love acidic conditions and are particularly sensitive to hard water. 

Hard water contains sodium bicarbonate and is actually toxic to your azalea. It is important to find out what kind of water your area has. 

If it is hard water, use bottled or mineral water to water your azalea. Azaleas thrive best when watered using rainwater.

If it is possible where you live, try to collect rainwater and use it to water your azaleas.

DRAINAGE

One of the biggest mistakes with azaleas, and indeed all indoor potted plants, is leaving the plant in standing or stagnant water for long periods. 

One of the main causes of this is using a pot with ineffective drainage. If the plant doesn’t have adequate drainage, the roots and soil will become sodden, leaving to the dreaded blackening of the leaves.

How to Fix Draining Issues

To allow the roots to drain, use a pot that has draining holes. To improve the drainage, you can put a shallow layer of gravel at the bottom of the pot.  Azaleas prefer a soil that is loamy to retain the moisture.

INCORRECT FERTILIZER APPLICATION

It can be easy to assume that all plants love being fed regularly, but azaleas don’t generally need a lot of fertilizing and feeding. 

Overfeeding can actually damage your plant, and this can result in black leaves. The type of fertilizer is also very important when it comes to azaleas, as using the wrong one will damage your plant.

How to Apply Fertilizer  

To apply fertilizer correctly, check your azalea’s regularly for new growth. Only use fertilizer when you see new buds and leaves beginning to grow. 

Make sure you choose one that is specifically made for plants that prefer acidic conditions. Try to use a plant food that is high in phosphorus and contains iron, as this will give the best results.  

It is important to half the dose stated on the bottle when feeding azaleas. Never use fertilizer on your azalea more than once a fortnight, as overdoing it will cause blackened leaves.

ENVIRONMENT

Azaleas can be very picky about their living conditions. They prefer temperatures between 50-60°F (10-15 °C). 

They thrive in bright, but indirect, sunlight. An ideal place for your azalea is on the porch, but only during summer months. 

Windowsills can be great places for your azalea but must be treated with caution.  The constant sun and heat can quickly dry your plant out.

How to Fix the Environment

If your home has dry air, it is important to give the plant extra moisture and humidity. There are several ways to do this. 

One option is to buy a humidifier for your home. As humidifiers can be expensive, this is not an ideal solution.

Luckily, there are ways to do this for free. One of the best ways is to leave your azalea in the bathroom after you have used the shower. 

It is important to not leave your azalea here as it will suffer if exposed to hot conditions for too long.  

You can also add humidity by using a small spray bottle of room temperature water and misting the plant regularly. 

Placing a small tray of damp pebbles underneath the pot is also an effective and cheap way to keep your azalea humid. 

This should ideally be done in the morning, so the moisture has a chance to evaporate and the plant doesn’t become sodden.

If you choose to place your plant on a windowsill, make sure you check it frequently for sun exposure and dry soil. 

Move the plant overnight as temperatures can dramatically drop here, adding stress to the plant. Anywhere too close to a radiator should also be avoided.

DISEASES

Indoor plants generally suffer less from diseases than plants grown outside. However, they can still affect your indoor plant, so they are something to be aware of.

The most common are root rot, leaf-spot disease,  and powdery mildew. Most of these won’t cause black leaves. 

However, if you find new markings on your leaves or anything strange, make sure you identify and treat the problem.

One of the best, and easiest, ways to avoid diseases attacking your azalea is good pot maintenance. Check the pot regularly for dead leaves and flowers, removing them immediately.

Cylindrocladium Blight

One disease that can cause the leaves to turn black is Cylindrocladium Blight. This disease causes the leaves to turn brown or black, and they fall off in 3-4 days. 

This disease can also affect the stem and roots. The best way to treat this is to remove any dead leaves and remove any infected areas. 

Make sure you are using tools that have been disinfected to avoid spreading the disease. You can do this at home by submerging the blade in boiling water.

Rhizoctonia Web Blight

This disease causes the leaves to change color from light brown to black. Although these spots begin small and can be easy to ignore, they quickly grow to cover the whole leaf. 

Once the leaf is infected, it will die and fall off. The best way to avoid this is to ensure the plant has a good, clean air supply with good ventilation. 

Watering in the afternoon should also be avoided. If your plant does become infected, you can also apply a fungicide.

PESTS

Indoor azaleas are attacked by pests less than outdoor plants, but pests can still be a considerable problem. One of the most common for indoor plants is spider mites. 

While these won’t cause black leaves, they will destroy your azalea before moving on to the next plant. 

Spider mites thrive in dry air, so maintaining humidity is key to minimize the risk.

Lace bugs

One pest that can turn your azalea leaves black is the azalea lace bug. The female uses the underside of the leaves to lay her eggs. 

When these eggs hatch, the new bugs use their mouths to such and pierce the leaves, extracting the chlorophyll. This lack of chlorophyll turns the leaves yellow. 

The small black spots are the fecal matter excreted by the bugs. The best way to control these is to check the leaves regularly and remove any eggs before they hatch. You can also use insecticides to control these bugs.

Azaleas are a fantastic addition to any indoor plant collection. Their intricate and vibrant flowers are a great way to bring beauty and color to any home. 

However, this can quickly turn to sadness if their leaves begin to turn brown or black. By ensuring you give your azalea the best conditions, you can avoid these dreaded black leaves creeping in.

Do you have indoor azaleas? What are your tips to keep the leaves full of life?

Arifur Rahman

I'm the owner of gardenforindoor.com. After completing my bachelor of science in agriculture, I'm serving as a civil service officer at the Department of Agricultural Extension, Bangladesh. I started Garden For Indoor to make your indoor gardening journey easy and enjoyable.

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