How to Fertilize Your Oak Tree (7 Simple Tips)

Oak tree leaves

A healthy, beautiful oak tree is surely a sight to see. If you really look at one, it almost seems unbelievable when you imagine how strong they are and how large they are! With canopies that spread the widths of houses and heights that mimic buildings, a healthy oak tree is all we can ask for. But, sometimes, our oak trees aren’t doing so well.

Young oak trees, saplings, and mature oak trees often can benefit from fertilizer. In truth, a good fertilizer for an oak tree consists of a 12-4-8 Nitrogen, Phosphorous, Potassium ratio. It’s best to spread fertilizer around your tree in the Spring, which is the best time to fertilize your tree.

Fertilizer is a quick and easy way to get your oak tree’s health back – and today, we are going to share some tips on how to do that. Keep on reading to find out how to fertilize your oak tree!

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Why Fertilizer is Great For Oak Trees

Fertilizer is sometimes necessary to maintain the health of your oak tree or bring your oak tree back to life. Simplistically, fertilizer is like vitamins, and when given in proper doses and at the right time – fertilizer can do wonders for your oak trees, but it can also do harm if it is not needed.

Fertilizers are made of minerals, natural/organic, or synthetic materials – all of which are created in a mixture combination that includes the multiple ingredients that your tree may be lacking.

Finding the right fertilizer is essential in ensuring the health of your oak tree, but more times than not, oak tree fertilizer consists of the three key ingredients: Nitrogen, Phosphorus, and Potassium.

Fertilizing sometimes seems daunting – but it’s way easier than you think! We’ve all been there where we think our plants and trees need water, but – sometimes that doesn’t work because it ends up just being that the oak tree is lacking in nutrients.

There are many ways to fertilize your oak tree, and today we are going to talk about how to do so!

How To Fertilize Your Oak Tree

There are a lot of things to consider when choosing to fertilizer your oak tree. There are so many different types of fertilizer available that solve all different problems, and it can be overwhelming to know exactly what you need.

We put together this guide to hopefully help you if you need to fertilize your oak tree.

Oak tree old eifel clouds hiking national park nrw landscape foliage

1. Determine The Age of Your Oak Tree

Apart from being unhealthy, determining the age of your oak tree is essential in deciding whether or not it needs to be fertilized.

● If your oak tree is a sapling or young – then yes, it can benefit from fertilizer.

● If your oak tree is young but newly transported – hold off until the roots establish.

● If your oak tree is mature, there is a good chance it doesn’t need fertilizer unless it shows signs of problems with its health.

You can learn more about oak tree age and how long oak trees live here.

2. Consider The Time of Year Before Fertilizing Your Oak Tree

If you have decided that your oak tree, in fact, needs fertilizer, consider the time of year before fertilizing.

The absolute best time to fertilize is always mid-spring. Why? Well, it’s because our trees are coming out of dormant stages, and it’s when they are going to be doing their best growing!

If you determine your tree needs fertilizer, the time you choose to fertilize is as important as the problem itself.

Fertilizing when trees go dormant will do nothing for the tree and can actually harm it.

If you fertilize when the weather is exceptionally warm, the fertilizer can react with the heat and burn the tree.

The best time to fertilize is the springtime because the soil is typically warm and dry, and new growth is coming, and all is good – right?

Think about coming out of a long nap and waking up and feeling groggy. You may need a little bit of water, maybe some sugar, maybe an immune boost – that’s exactly what happens with our oak trees, and when they start to gradually wake up, fertilizer will help them wake up and have the energy to grow strong!

If you still haven’t planted your oak tree, you can checkout our guide on the best time to plant oak trees.

3. Determine What Nutrient Your Oak Tree Needs

Before absolutely everything else, you have to determine what your oak tree needs. Different problems mean different fertilizers, and although more times than not, your oak needs Nitrogen, Phosphorus, or Potassium – that is not always the case.

If your oak tree is lacking in calcium, your tree may not be growing. If you notice that your oak tree, which typically grows 1-2 feet a year, has stopped growing – it may need calcium.

Fertilizers like CalMag Iron Liquid Plant Supplement can help bring some calcium back to your plants.

If your oak tree lacks iron, the leaves of your oak tree may be turning yellow. If you need an iron-rich fertilizer, you can try Lawn Star Liquid Iron.

If your tree branches are brittle – it may need nitrogen. A great nitrogen fertilizer is Lawn Star Liquid Nitrogen – just remember to always find slow-release liquid nitrogen, as it can harm the tree if it is too fast.

There are so many reasons as to why your tree may be unhealthy, or so many things it could be lacking in, so if your oak tree is really looking out-of-sorts, if you will, it’s important to call a professional, as they will know what your oak tree needs!

4. Find the Proper Dose of Fertilizer for Your Oak Tree

You can’t, however, just grab a bag of fertilizer, dump it on the soil, and let it be. Fertilizer comes in doses, just like medicine and vitamins, and needs to be properly dosed when added to our soil for our oak trees!

When you determine the fertilizer, make sure to read the instructions on the bag and follow them closely. It will tell you the dosing information, how much is needed, when is the best time, and the duration of fertilizing.

Dosing is important because if you put too much, you can damage the oak tree, and if you put too little, you may think you have helped the tree, but it may have done nothing to help the tree at all – which will just prolong the issue.

5. Spread The Fertilizer Around The Oak Tree

There are a few methods in applying fertilizer to your oak tree, and one of the tried-and-true methods is by spreading it around the bottom trunk. However, there are some things you need to keep in mind.

If you are going to spread the fertilizer around the trunk, make sure that you are at least 18 inches away from the base of the tree, to ensure a proper absorption rate. If you apply the fertilizer too close to the tree, you can burn the trunk, and there’s a chance that the fertilizer will not be absorbed.

Spreading the fertilizer based on the dosing but ensuring that the soil has a good layer atop it is a good way to quickly and efficiently fertilize your oak tree.

6. Dig Holes Around the Oak Tree and Fill Them with Fertilizer

The ideal way to fertilize your oak tree would be the method of digging holes and filling those holes with fertilizer – but yes, it is more time-consuming.

Starting 18 inches away from your tree and digging holes about the size of a quarter, around the trunk of your tree, and out, and then filling those holes with the fertilizer, is the best way to fertilize your oak trees.

The fertilizer will get down into the soil, approaching the roots of the trees, and is more protected from wind and other problems that can occur at the surface.

This method will also ensure the health of any nearby plants and grass, as the fertilizer for an oak tree may be different than what is needed for the other plants.

Although time-consuming, this method may save you a lot of trouble in the long run because it is way more effective, and the fertilizer will really get down into the deeper parts of the soil, where the roots remain.

7. Add Water After You Fertilize An Oak Tree

After fertilizing, it is so important to add water to your oak tree.

Adding water to the fertilizer helps the soil absorb the fertilizer, and the water becomes the means of transportation.

Imagine throwing dry fertilizer on dry soil. It’s going to sit there until it rains, and the soil will never absorb it.

Adding enough water without overwatering is key to allowing the fertilizer to be absorbed by the soil and will allow it to quickly get down to the roots.

6 Ways To Tell If Your Oak Tree Needs Fertilizer

One way to decide if your oak tree needs fertilizer is by knowing the stage of life that it’s in. Your oak tree may not need fertilizer if it is mature but will if it’s unhealthy, and young oak trees will always benefit from fertilizer.

Most of the time, mature oak trees don’t need fertilizer. They are well established, making acorns, and have the science of survival – down pat. But, although oak trees are not typically susceptible to disease and are generally healthy trees – things happen from time to time, and there are a few tell-tale ways to know if your oak tree needs fertilizer.

Oak tree in full leaf in summer standing alone

1. If Your Oak Tree is Young

We say this without hesitation, if your oak tree is young and, in a nursery – it needs fertilizer!

Young trees are often being prepared for transportation. A young oak tree needs a lot of care and attention – and the truth is – the best time to fertilize an oak tree is when it is growing!

Fertilizer will give a young oak tree all the nutrients it needs, especially if it’s in a nursery, and fertilizer will prepare it and make it strong for transport.

If you have a sapling oak tree, make sure you’ve planted it in the best possible spot for it to thrive. Take a peakski at our guide on the best places to plant an oak tree.

2. When Your Oak Tree Establishes Roots After Transport

It’s important to understand that when your oak tree is first transported, it may be a good idea to wait it out before throwing fertilizer on the oak tree.

We are all tempted to add fertilizer quickly because we think it’s some magic potion to help the oak tree grow – and yes, it’s kind of magic, but it needs to be done right.

When an oak tree is first transported, the tree is in a state of shock. It doesn’t know up from down, left from right – it feels “all over the place,” as us humans would say.

If your oak tree is in a state of shock, it’s not going to be functioning properly. It’s as if we are telling someone to relax and enjoy some food when they are completely stressed out – it just will not happen.

Giving your oak tree some time to sort things out on its own, but of course, with a lot of water, will be beneficial for its health and will allow the shock to pass.

When the roots are then established – then you should fertilize the tree.

3. If Your Mature Oak Tree Isn’t Producing Acorns

If your mature oak tree isn’t producing acorns, it may need fertilizer. At about 20 years of age, oak trees should be producing acorns.

An oak tree generally produces up to 1,000 acorns a month and 1,000,000 in its lifetime. However, if your oak tree is unhealthy, it’s not going to be able to produce acorns.

Acorns are an essential part of our ecosystem, and they are the food of many different animals. One oak tree alone can house an entire life cycle, but an oak tree has to be healthy in order to do that.

4. If Your Oak Tree Has Yellow Leaves

Apart from the autumn season, because it may be hard to tell then if your oak tree has yellow-colored leaves, there is a good chance it needs to be fertilized.

Yellow leaves mean that something is going on with the health of your oak tree. However, in this case, your soil levels may be lacking in iron – and unlike the general three ingredients used for oak trees – you may have to get a fertilizer rich in iron.

A good fertilizer that is rich in iron is Espoma Iron Tone Fertilizer and may help rectify this problem.

5. If Your Oak Tree Has Brittle Branches

A quick and efficient way to determine if your tree is healthy or not is by looking and feeling its branches!

A healthy oak tree’s branch is flexible and bendable. If you bend an oak tree’s branch and it snaps in half, that means it’s brittle and most likely means you need fertilizer.

Typically, if your oak tree’s branches are brittle and snapping, your oak tree may be lacking in nitrogenHastaGro 12-4-8 Liquid Lawn Food Plus is an ideal oak tree fertilizer that will help bring back the health of your oak tree.

6. Your Oak Tree’s Canopy Isn’t Full

Another way to determine if your oak tree needs fertilizer is to look at its canopy.

If an oak trees’ canopy is bare in spots, and seems to be missing larger chunks of leaves here and there, your oak tree may be lacking in nutrients.

Sometimes, when our oak trees need fertilizer, the leaves of the tree do not grow to their expected size; they remain tiny and will be frailer. This can leave branches looking bare and an oak trees’ canopy to be spotty.

Best Types of Oak Tree Fertilizer

If you now have completely determined that it is time to fertilize your oak tree, there are three types of fertilizer that you can consider: Mineral, Organic and Synthetic.

Mineral fertilizer is made from naturally occurring minerals. Nitrogen, Phosphorus, and Potassium are considered mineral fertilizers.

Organic fertilizer is created from organic substances. Leaves, manure, bone, shells, rocks, other plants – basically anything organic, are ground up and used for fertilizer.

Synthetic fertilizer is exactly what it seems like – it’s manufactured ingredients that target specific problems.

If you’re interested, you can read our piece on the best oak tree fertilizers here.

That’s a Wrap!

If your oak tree seems to be lacking, quit slacking! It’s the truth because the faster you act on it, the more of a chance you have to save your oak tree and bring it to good standing.

Oak trees, although resilient, not susceptible to disease, and require little to no maintenance when mature, still need fertilizer from time to time and can benefit from a boost of nutrients.

It’s important to maintain an oak tree’s health because these larger-than-life trees can fall down if they become unhealthy and can cause harm to your outdoor spaces, belongings, your home, or you.

If you suspect a nutrient deficiency with your oak tree, it is always best to check in with a professional and have them determine the best fertilizer and plan of action.


“Oak Tree Care: Oakland FL.” Oak Tree Care | Oakland FL, 

Jordan, D., Ponder Jr, F., & Hubbard, V. C. (2003). Effects of soil compaction, forest leaf litter and nitrogen fertilizer on two oak species and microbial activity. Applied Soil Ecology23(1), 33-41.

Gilman, E. F., Yeager, T. H., & Kent, D. (2000). Fertilizer rate and type impacts magnolia and oak growth in sandy landscape soil. Journal of Arboriculture26(3), 177-182.

Tree Owner’s Manual – USDA. 

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