Azalea Fertilizer Guide

It’s undeniable that this genus of flowering shrubs is one of the most outstanding you’ll ever have as a bonsai. There are several species and cultivars prized for their bright, colorful blooms. However, you need to know which Azalea fertilizer to use for the best results.

Join us as we show you how best to feed your Azalea bonsai.

azalea fertilizer

Here are the topics in this article:

Here are the topics in this article:

The Best Fertilizer for Azaleas

There are plenty of Azalea fertilizer products on the market, whether you buy them locally or online. Many people will tell you that you can use standard food for your bonsai, but this statement isn’t completely true. You need a different balance of nutrients if you want your flowers to show off when the summer arrives.

Choosing the best fertilizer for your Azalea bonsai depends on several factors, which we’ll discuss here.

Time of Year

Your Azalea bonsai will enjoy feeding when it starts producing new growth. You can start providing fertilizer when you see new buds in spring and continue to do so when the first blooms appear in summer.

If you’re lucky and there’s a second spurt in early autumn, continue to give it food so it has enough for when winter arrives. If you have deciduous Azaleas, stop fertilizing when the cold sets in and it goes into dormancy. It gives your bonsai tree a chance to rest.

Type of Soil

Your soil will already have some nutrients in it. You can get testers to check the various levels, but you should ask your supplier what the nitrogen, phosphorous, and potassium (NPK) balance is. They can also tell you what other micro-nutrients it contains.

Once you know these details, you’ll have a better idea of which Azalea fertilizer to buy. Remember, as you water and the bonsai feeds, the soil will lose these nutrients, so you should adjust the balance as time goes by. You’ll also know which type will be best for you, which we’ll deal with in a moment.

Structure, Foliage, or Blooms

Each of the major nutrients performs a specific function. Nitrogen plays a role in helping your Azalea grow faster and develop the green foliage quicker. Phosphorous gives your stems and branches more strength, while potassium focuses on flower and seed development. While we recommend a balanced approach, you may need to see which one your tree needs the most when buying a fertilizer.

Location and Lighting

Where you place your Azalea bonsai also has an impact on which fertilizer will work the best for you. If you put it outside to absorb as much morning sunlight as possible, you may need to feed it more than usual so it has enough strength for photosynthesis. When you keep it indoors, how much food you apply will depend on how much natural sunlight you provide.

azalea fertilizer

Types of Azalea Fertilizers

Now that you know what to look out for when buying Azalea fertilizers, it’s time to see how many types there are for your bonsai. You’ll notice different descriptions on the labels, and we’ll provide some of the details so you don’t remain confused.

Liquids and Solids

It’s up to you whether you want to use water-soluble solutions or solid products. When aiming for the liquid types, you’ll apply it to your watering can via dilution, feeding your Azalea bonsais more regularly. You’ll generally apply the fertilizer once a week.

For the solid Azalea fertilizer, you’ll find pellets and food spikes. These release slowly and can last you for the entire season. However, you’ll have to see if the sunlight causes them to disintegrate quickly, in which case you may need to reapply them.

Nitrogen Focus

When you’re wanting to develop the foliage quickly over spring, you can buy Azalea fertilizer with high nitrogen levels. You’ll see the first number in the ratio is much higher than the others, such as 15-5-5. It’s best if you only apply this food over spring before the flowers start to appear.

One aspect you need to consider with nitrogen-rich fertilizer is that it may cause the leaves to burn when in direct sunlight. When you see signs of this on your Azalea bonsai leaves, either move the tree away from the light during the peak afternoon or reduce the feeding.

NPK Balance

For the best results in summer and early autumn, we recommend an Azalea fertilizer that has a balanced NPK approach, such as 5:5:5 or 15:15:15. It will ensure that your bonsai tree can develop branches, leaves, and flowers at an equal rate.

This food ensures that any soil without nutrients has the perfect nutrients, but you shouldn’t apply it if you bought new soil that already has the minerals supplied.

Controlled Nitrogen Release

When you want to control the duration of nitrogen release, you can use the pellets or spikes with higher N levels. The benefit of this fertilizer for your Azalea bonsai is that it usually has higher levels of needed micro-nutrients, such as calcium and magnesium. Together with potassium, they aid in cell metabolism and absorbing food and water from the soil.

Slow Release

Finally, there are other forms of organic fertilizers that take longer to release than pellets or spikes. They decompose into the soil, giving your Azalea the chance to absorb them when necessary. The food is usually covered in sulfur polymers or plastic resin, and the heat and sun break them down into the soil, so they only feed your bonsai when it’s hot and sunny.

azalea fertilizer

Alternative Azalea Fertilizers

If you don’t like buying the liquid or solid Azalea fertilizers at the shops or online, there are other ways you can feed them. Many people use these items to feed their bonsais, but you’ll need to do so in limited amounts. We’ll quickly discuss their pros and cons so you can decide for yourself which one is best.

Coffee Grounds

When coffee grounds have been brewed for your to drink, you can use the remaining product as a fertilizer for your Azalea bonsai tree. They are highly acidic, which is what these species love. If you’re struggling to lower the pH levels for more acidic levels, this is one of your best options to improve the situation.

The only concern is that it may cause problems if you’re already supplying nitrogen-high food to your Azalea. It prevents the phosphorous from doing its job in producing flowers, so you may see fewer blooms in summer.

Still, coffee grounds are excellent for preventing and reducing fungal growth in the soil and on your bonsai tree. So if you’re seeing any diseases or the acid levels are too low, we recommend using this item for at least two feedings or until conditions improve.

Epsom Salts

Another way of adding acidity to the soil is adding Epsom salts. It has magnesium and sulfur in it, which combats high phosphorous levels. The nutrients will assist in absorbing food more effectively, and you’ll see more flowers and greener leaves.

We recommend using Epsom salts as Azalea fertilizer only once a month in summer. Too much of it can cause damage to the tissues of your bonsai tree, and you may see the leaves and branches dying. As with everyone in life, moderation is key to success.

Banana Peels

These banana peels are an excellent way of both lowering the pH level and adding some nutrients to the soil, mainly potassium, magnesium, phosphorous, and calcium. It’s ideal if you have too much nitrogen and you need a solution to fertilize your Azalea bonsai without it.

While you can place the peels on the soil to decompose slowly, here’s a method of making vinegar for better results:

  1. Boil two pounds of peels in four cups of water for 30 mins in a large pot
  2. Remove the peels and wrap them in a cheesecloth
  3. Squeeze the banana peels until all the liquid drops into the pot
  4. Add four more cups of water to dilute the mixture with 1.5 cups of sugar
  5. Stir and then boil for another 15 minutes
  6. Place in a sterilized container and add half a teaspoon of baker’s yeast
  7. Close the jar and leave it for seven days
  8. Add one cup of vinegar starter and leave for three weeks
  9. Place the banana vinegar in a pot and put cheesecloth over the container
  10. Pour the vinegar back into the jar over the cheesecloth so it can remove sediments and yeast
  11. Close the jar and leave for four weeks
  12. Open the container and pour the vinegar into the large pot, boiling for ten minutes
  13. Place it back in the jar and leave it to cool. You can now fertilize your Azalea with it, and it makes about 8 cups
  14. If it’s too strong, you can dilute it with more water


When you need some calcium for your Azalea bonsai, you can use eggshells. As an idea, one eggshell provides one teaspoon, which is about 750 mg calcium. This nutrient helps with cell development and structure, making your tree stronger on the inside.

You can either crush them or make them into a powder and apply the result to your soil. Make sure you wash and dry the shell pieces first so that they don’t attract pests. You’ll find stunning flowers in summer, while it also reduces the chances of rot on your blooms.

azalea fertilizer

The Right Time to Apply Azalea Fertilizer

The primary concern of the right season to feed your Azalea bonsai is whether you have an evergreen or deciduous species. For the former, you’ll aim for late fall into early spring. For the latter, it’s best to give it fertilizer in early summer when the flowers are about to go into full bloom.

When it comes to the right time of day to apply Azalea fertilizer, we recommend the late night or early morning. When the sun arrives and provides the necessary heat and light, your bonsai tree will start using the energy for photosynthesis and developing new growth. By this time, the food should already be in the soil, ready to be processed.

How To Feed Your Azalea Bonsai

While knowing which is the best fertilizer will help you feed it properly, you’ll need to know how to apply it to the soil of the Azalea bonsai. Here’s a quick summary:

  1. Decide if you want to use a liquid or solid Azalea fertilizer
  2. Look at which nutrients you need, but we recommend a balanced NPK
  3. Check the area of the pot that the foliage stretches over, as the roots will likely cover the same surface
  4. Apply the fertilizer across the same surface area as the foliage to encourage the roots to extend into the soil
  5. Only fertilize in the morning and during the required season

The Top Benefits of Azalea Fertilizer for Bonsais

While we’ve mentioned some advantages of Azalea fertilizer for your bonsai tree, there are some others we should mention. We’ll place everything together in one section so you can analyze them:

  • Encourages dense and gorgeous leaves and flowers
  • Strengthens the trunk, branches, and cells
  • Improves acidic levels of the soil
  • Promotes strong root development
  • Helps nutrient deficiency in the soil
  • Fights pests and diseases
  • Short- and long-term feeding options
  • Some are safe for pets who decide to drink from the tray
  • There are products with probiotics to assist with droughts
  • Available for indoor and outdoor Azaleas

Is Miracle-Gro Good for Azaleas?

There are actually   that are specifically designed for Azaleas and Rhododendrons. While you’ll dilute it in water, it can last up to two weeks when applied correctly. It mostly assists with helping to increase the acidic levels in the soil and promoting greener leaves and brighter flowers.

azalea fertilizer

Can You Over Fertilize Azaleas?

Providing fertilizer at the wrong times of the year or too much can damage your Azalea bonsai. Deciduous species need to rest during winter to store energy and prepare for the upcoming spring. If you continue to feed it, it will continue to grow leaves and branches and will become weaker over time.

As a consequence of overfeeding Azaleas, the following may happen:

  • Stunted growth
  • Dried or burned leaves
  • Pests attack the weakened tree
  • Wilting or yellow leaves
  • Sudden death of the plant

Tips and Tricks for Fertilizing your Azalea Bonsai for Healthy Blooms

Before you leave this page, we’d like to share some tips when applying Azalea fertilizer to your bonsai tree. These tricks will save it from suffering any damage and stress and will promote a longer lifespan.

  1. Refrain from fertilizing your Azalea bonsai again until you see that the leaves have slowed down in developing
  2. Don’t add fertilizer to the water when the heat is excessive and there are drought-like conditions; it will need water more than food
  3. If you decide to use mulch like wood-chip sawdust, we recommend fertilizing more regularly
  4. Test your soil if possible to check which nutrients are needed, or aim for a balanced approach
  5. Organic fertilizers are much better than chemical ones for the health of your Azalea
  6. If the acidic levels are low (more on the alkaline side, higher pH), use food that improves the conditions

azalea fertilizer

Final Words

As you can see, using Azalea fertilizer isn’t as simple as just throwing it on the soil and hoping for the best. There are strict guidelines you need to follow if you want your bonsai to remain strong and healthy. Moreover, you can change the consistencies if you want to change the focus from leaves to flowers.

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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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