7 Best Apple Tree Fertilizers (And How Often To Use Them)

Apple trees are an amazing addition to the yard that provide beautiful spring blossoms, summer shade, and fall fruit harvests. Whether you have an established apple tree or you’re thinking of planting one, you may be wondering what the best apple tree fertilizers are for your needs!

The most important nutrients in apple tree fertilizers are nitrogen, potassium, and calcium. The best apple tree fertilizer types are:

• General-purpose fertilizer
• Sulfate of potash (0-0-50)
• Potash-magnesium (0-0-22)
• Organic fertilizer
• Fertilizer spikes
• Liquid fertilizer
• Boron (only needed every 3-4 years)

Fertilizers are an important part of keeping your apple tree healthy. Below, we’ll go over the BEST apple tree fertilizers and give you some tips on how (and when) to use them!

How Does Fertilizer Help Apple Trees?

All trees require 16 essential nutrients to grow, produce fruits and flowers, and generally remain healthy. While this is true of all trees, each tree species relies a little more heavily on certain nutrients.

Apple trees require lots and lots of nitrogen, potassium, and calcium. These nutrients are used to create energy that is used to make fruits, flowers, new shoots, and root growth.

As an apple tree uses the nutrients from the soil, they are not always replaced as quickly as they are taken up. That’s where fertilizers come into play. 

Fruit Production Requires A Lot Of Nutrients

Not all trees require fertilizer, but apple trees and fruit trees in general usually need an application of fertilizer once or twice a year.

The reason is fruit production. Growing fruit requires a LOT of energy and nutrients! During the growing season, these nutrients are used faster than they can be replaced.

Fertilizers help replace the nutrients that the apple tree uses so that it can continue to grow and produce fruit without pause.

When there is a lack of nutrients in the soil, apple trees will slow fruit production and focus more on low-energy costs such as shoot growth or leaf production.

Apple Trees Are Nutrient Hogs

Apple trees can be pretty demanding of the environment where they are growing. They have five basic systems that need nutrients:

• Shoot growth
• Root growth
• Flowers
• Fruit
• Leaves

All of these systems require nutrients and water to continue growing and to stay healthy.

While almost all trees have the same five systems, apple trees are more demanding than most because they produce such large fruits.

According to Oregon State University, most fruit trees are considered ‘heavy feeders’ that displace a high volume of macronutrients. Macronutrients include nitrogen, phosphorus, and potassium.

Each macronutrient helps the apple tree in different ways. For example, nitrogen is used more for growth while potassium is more involved in resisting pests and hardening off for winter.

As you can see, every nutrient plays a role in the health and fruit production of an apple tree, and these hogs will use every bit of nutrients they can find in the soil!

Apple Trees Must Make A Lot Of Leaves

Apples may be the most important part of the tree for most gardeners, but there’s a lot that goes into an apple tree producing a fresh, ripe apple that isn’t spoiled or sunburnt.

Leaves play a big part in the overall health of an apple tree as well as proper fruit production. To make leaves, apples need nutrients!

Fertilizers help apple trees to fill out and produce plenty of leaves. In turn, these leaves protect ripening apples from getting sunburned.

Yes, fruit can get sunburned!

According to the University of Minnesota, sunburn happens most frequently during hot, sunny weather and is more likely to affect apples on the outside of the tree than the inside. This is because the apples on the inside of the tree are protected by the leaves.

Apple Trees Need Strong Roots

Roots are an important part of every tree. We don’t usually see roots, so sometimes we forget how important they are!

Fertilizers help encourage growth both above and below the soil.

Roots are important to apple trees for a few reasons:

• Anchor the apple tree in place
• Stabilize the apple tree so it doesn’t blow over in a storm
• Absorb water
• Absorb nutrients

Adding fertilizer to the soil can help roots grow faster, thicker, deeper, and wider so that even when there is a dry spell, the tree will be able to reach a water source.

You must also make sure that your apple tree has PLENTY of sunlight.

Best Fertilizers For Apple Trees

The best way to tell what nutrients your apple tree needs is by doing a soil test. This will not only tell you what the soil is lacking, but it will also tell you the pH of your soil.

For apple trees, you want the soil to be a little bit acidic, around 6-6.5. If your soil pH is higher, you can use something like Bloom City Professional pH Down Liquid Fertilizer to bring the pH down.

If the pH is less than 6, you can apply lime to help bring it up. Check the pH often after applying either lime or an acidifier to make sure you’re in the right pH range.

Once you get the pH figured out, it’s time to move on to fertilizers. 

We’ll go over the specifics below, but you can refer to this table as a general overview of all the different kinds of fertilizers:

General Purpose Fertilizers Work Great

Not everyone has the time or funds to take a soil test. Sometimes, you just want to give your apple tree a boost without worrying about specific nutrients.

We totally get it!

That’s where general-purpose fertilizers come in. They are an excellent choice if you’re not sure what kind of soil you have in the yard.

Southern Ag All Purpose Granular Fertilizer has an NPK ratio (%nitrogen, %phosphorous, %potassium) of 10-10-10 which is very typical of all-purpose fertilizers. 

This particular fertilizer comes as granules that look like small pellets. They can be spread around the dripline of your tree.

Follow the directions on the label for the proper amount to apply. This is generally equal to ½ cup for every inch of trunk diameter.

General-purpose fertilizers are great to use when your apple tree isn’t growing as fast as you’d like. According to the University of New Hampshire, any apple tree that grows less than 8 inches per year should be treated with a general-purpose fertilizer.

Potassium Sulfate Works Great For Apple Trees

We’ve established that apple trees benefit from fertilizer, but choosing the right fertilizer can be a tricky topic!

Potassium sulfate is a type of fertilizer that contains both potassium and sulfur that are ready to be absorbed by the tree as soon as it enters the soil.

Unlike general-purpose fertilizers, potassium sulfate should only be used if there is a potassium deficiency in the soil. Potassium sulfate, also called sulfate of potash, has an NPK ratio of 0-0-50, meaning it doesn’t have any nitrogen or phosphorous.

Alpha Chemical’s 5 Pounds – Potassium Sulfate comes as granules that can be applied to the soil around your apple tree to improve potassium and sulfur deficiencies.

There are a few advantages to using potassium sulfate over other potassium fertilizers:

• Contains less chloride: apple trees, along with many other fruit trees, are sensitive to the chlorides that get added to many other fertilizers.
  
• Improves yield: potassium sulfate can help increase the number of apples produced each year and provide firmer apples.
  
• Sulfur: sulfur is not as important as the 3 big macronutrients, but it’s considered a secondary nutrient that helps in seed formation and the overall health of apple trees.

Potash-Magnesium Can Work Well On Apple Trees

Potash-magnesium, also known as sul-po-mag, has an NPK ratio of 0-0-22. Again, it contains no nitrogen or phosphorous.

The difference between potash-magnesium and sulfate of potash is that this fertilizer contains magnesium. Like sulfur, magnesium is not as important as the macronutrients but it’s still considered more important than the micronutrients.

Potash-magnesium is another fertilizer that should be used only when there is a deficiency in the soil. However, even if you didn’t get a soil test, there are some tell-tale signs that you need this type of fertilizer:

• Early fruit drop: This is not uncommon on healthy apple trees, but if premature fruit drop occurs in combination with other signs, it may be because the soil is deficient in magnesium.
  
• Tiny fruit: If your apples look more like grapes than apples, there may be a magnesium deficiency.
  
• Early ripening: Apples should be ripe enough to pick around September, give or take a month. If your apples appear to ripen in the middle of summer, it may be due to a lack of magnesium.

If you’re noticing any of these signs on your beloved apple tree, it might be time to stock up on some sul-po-mag!

Greenway Biotech’s Sul-Po-Mag 0-0-21.5 Sulfate of Potash Magnesia comes in a 3-pound bag with crystal granules that appear similar to coarse salt.

Read the label and directions for the proper amount to apply to your apple tree.

Organic Fertilizers Can Be Used For Apple Trees

Most of the fertilizers we’ve talked about so far are inorganic, meaning, they’re synthesized in a lab or factory.

Organic fertilizers are made from natural things like plants, animals, and animal waste. They’re a great choice if you want to skip all the synthetic and chemical fertilizers out there and go for a more natural approach.

Down To Earth’s Organic Fruit Tree Fertilizer Mix is designed specifically for fruit trees. It has an NPK ratio of 6-2-4 and comes in a 5lb box made of recycled cardboard.

Some of the ingredients in this fertilizer include natural items like:

• Feather meal
• Fish bone meal
• Calcium carbonate
• Alfalfa meal
• Kelp meal

This specific fertilizer also contains calcium and magnesium, two nutrients that are essential to the health of your apple tree.

Fertilizer Spikes Are An Easy Option

Fertilizers can be annoying to deal with. The granules must be spread around the dripline and can be dusty while liquid fertilizers must be added to water.

Fertilizer spikes are probably the simplest of ways to fertilize. You simply place the spikes in the ground and let them slowly dissolve in the soil, providing your apple tree with nutrients over a longer period.

Spikes are a good choice if you’d rather employ a ‘set and forget’ method of fertilizing. Miracle-Gro’s Fruit & Citrus Plant Food Spikes come with 12 spikes. The number of spikes needed will depend on the diameter of your apple tree’s drip line.

For example, an apple tree with a 10-foot diameter drip line will need 7 spikes according to the package directions.

The NPK ratio of these spikes is 15-5-10, which is close to a general-purpose fertilizer but has the added benefit of slowly releasing the nutrients over time instead of a quick burst.

The only time fertilizer spikes are not the best option would be if you have a specific nutrient deficiency or if you want a quick fix. These spikes are meant to be slow-releasing and will not fix a severe nutrient deficiency anytime soon!

Liquid Fertilizer Is A Good Option

Fertilizers come in all sorts of shapes and sizes. Some are in pellet form, others crystal, and still, others come in liquid form.

Liquid fertilizers are meant to be diluted with water and applied to the soil or sometimes directly to the leaves of your apple tree. These types of fertilizers are water soluble, meaning they can be absorbed directly into the tree for a quick boost of nutrients.

Liquid fertilizers are a good choice if you notice a specific nutrient deficiency in your apple tree and want a fertilizer option that will be immediately available to your tree. 

In essence, liquid fertilizers are a “quick fix’”fertilizer.

AgroThrive Fruit and Flower Organic Liquid Fertilizer comes in a 32 oz bottle and has an NPK ratio of 3-3-5. This fertilizer must first be diluted with water before applying it to the soil.

Honorable Mention: You Might Need Boron!

While boron isn’t exactly a fertilizer, it’s worth mentioning that apple trees, specifically, will need a boost of boron once every 3-4 years.

If you’re opening your apples and seeing small, round, brown splotches in the flesh, your apple tree is deficient in boron. To fix this issue, it’s recommended to spread 1 cup of borax every 3-4 years or when you notice brown spots inside your apples.

How And When To Fertilize Your Apple Tree

Knowing how to use your fertilizer is almost as important as choosing the right fertilizer. Most commercial fertilizers will come with directions on the package label, so be sure to give those a look before using them on your apple tree.

According to Clemson University, the main roots that use fertilizer will typically be located in the top 10 to 14 inches of soil. This is a good thing to keep in mind as you do not need the fertilizer to sink deeply into the soil.

Additionally, if you’d like some suggestions, here are some of the easiest apple tree varieties to grow!

Water After Fertilizing

No matter which kind of fertilizer you decide to go with, it’s a good idea to water the soil after you apply it to the soil.

Watering will help work the fertilizer into the soil so that it becomes available to the roots of your apple tree.

If you don’t water the soil soon after fertilizing, it’s possible for the fertilizer to either blow away or react with the elements in the air and morph into something unusable by your apple tree.

Alternatively, you can wait to use fertilizer until you know it will rain and let nature take care of it!

Create A Regular Fertilizing Schedule

Getting on a regular fertilizing schedule will help keep your apple tree healthy.

Apple trees should be fertilized twice a year. It’s recommended to apply once in April and again in June.

Fertilizer applied in April should be before the tree begins to bloom. The fertilizer will help give your apple tree the nutrients it needs to produce flowers without running out of the nutrients it has stored up since winter.

The application of fertilizer in early June will help with fruit production. Apples take a lot of nutrients to make! Fertilizers will help your apple tree obtain the necessary nutrients to make those delicious red apples!

By applying fertilizers on a regular schedule, you’ll be providing your apple tree with the nutrients it needs at the right time.

Do Apple Trees Need Fertilizer Every Year?

So far, we’ve talked a lot about all the different fertilizers for apple trees and how to apply them, but we never talked about IF you should apply them.

Under normal circumstances, an application of fertilizer twice per year is great for your apple tree. However, there are some instances when you do not need to apply any fertilizer to your apple tree.

Identifying when and if you need fertilizer can be just as important to your apple tree’s health.

Apple Tree Growth Is An Indicator 

The overall growth of your apple tree is an excellent indicator of the need for fertilizer. If you apply fertilizer when the tree already has enough nutrients, you could risk root burn or an apple tree that focuses more on producing leaves than fruits.

If your apple tree is exceeding 8 inches of growth per year, you typically will not need to fertilize it unless it is showing specific deficiency symptoms.

When your apple tree is growing less than 8 inches per year, it’s a safe bet that a dual application of fertilizer will do it some good!

Look For Signs Of Deficiencies

Trees are pretty good at letting us know when they’re not getting enough nutrients or water from the environment.

Apple trees have a few telltale signs that they are lacking in certain nutrients:

• Yellowing leaves: leaves that have a yellow or bronze outer edge are likely lacking in potassium or magnesium.
  
• Pale leaves: pale leaves are an indication of nitrogen deficiency.
  
• Stunted growth: If your apple tree is slow-growing, it may be due to a nitrogen deficiency.
  
• Low fruit yield: this could be due to a lack of several different nutrients.
  
• Weird-shaped fruit: This is most likely caused by a boron deficiency.

If you notice anything off about your apple tree, it may need a fertilizer application. If the symptoms come on suddenly, a liquid fertilizer might be your best choice as this will be absorbed quickly by your apple tree.

Other slower-developing symptoms may be treated with an all-purpose fertilizer or a slow-release fertilizer such as spikes or potassium sulfate.

It’s not recommended to apply fertilizer too early or too late in the season. This can prevent apple trees from hardening off for the winter and will do more harm than good.

That’s A Wrap!

Apple trees make a great addition to the yard and can provide you and your family with more fruit than you could possibly eat each year!

Fruit production depends a lot on how many nutrients are available to your apple tree. Applying fertilizer regularly can help ensure your apple tree thrives each and every year!

While it may seem like you have endless options when it comes to fertilizers, which one you choose is largely based on the needs of your apple tree.

A soil test can help reveal what kind of nutrients are present in your yard and what kind of fertilizer might be best for your apple tree.

You can always talk with your local arborist who may have an idea of what the soil in your local area is like and they can recommend a good fertilizer to use for your apple tree!

If you have an old tree, take a look at the reasons why you may need to cut down your apple tree, along with the best time to do it!

References

Aguirre, P. B., Al-Hinai, Y. K., Roper, T. R., & Krueger, A. R. (2001). Apple Tree Rootstock and Fertilizer Application Timing Affect Nitrogen Uptake, HortScience HortSci, 36(7), 1202-1205.

Kopytko, P., Karpenko, V., Yakovenko, R., & Mostoviak, I. (2017). Soil fertility and productivity of apple orchard under a long-term use of different fertilizer systems. Agronomy Research, 15(2), 444-455.

Li, J., Liu, Y., Tang, Y. et al. Optimizing Fertilizer Management Based on Controlled-Release Fertilizer to Improve Yield, Quality, and Reduce Fertilizer Application on Apples. J Soil Sci Plant Nutr 22, 393–405 (2022).

Murtić, S., Oljača, R., Koleška, I., Čivić, H. (2017). Apple Quality and Calcium Content as Affected by Fertilizer Treatment. Polish Journal of Environmental Studies, 26(5), 2107-2111.