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Oak Tree Fertilizer: How and When to Fertilize

Oak trees are very hardy trees and provide excellent shade. The oak is one of my favorite trees. In fact, we have several oak trees where we live. Usually, a mature oak tree will not need fertilizer, but a young oak tree will need fertilizer to grow properly. In this article, I will explain all about oak tree fertilizer.

Choosing the right oak tree fertilizer can significantly impact the tree’s health and vitality. Fertilizers provide essential nutrients that may be lacking in the soil, promoting robust growth, vibrant foliage, and increased resistance to diseases and pests. Continue reading to learn all about how and when to fertilize oak trees.

What Kind of Fertilizer for Oak Tree

A mature and thriving oak tree typically does not need extra feeding in its natural environment. Decomposing leaves and other organic materials on the ground provides the necessary nutrients. As these materials decompose, they release nutrients into the soil, feeding the tree’s roots.

You might consider adding extra fertilizer if the natural organic materials are cleared away, if the oak tree shows signs of disease, or if its growth is poor. Typically, younger oak trees can benefit from fertilization to help them establish themselves more rapidly.

The primary nutrient an oak tree needs is nitrogen to support foliage development. An NPK 15-5-10 fertilizer is perfect for fertilizing oak trees. NPK stands for Nitrogen, Phosphorus, and Potassium. In this case, the oak fertilizer contains 15% Nitrogen, 5% Phosphorus, and 10% Potassium.

Nitrogen is essential for promoting leafy growth and the development of vibrant green foliage. Phosphorus is vital for strong root development, flower and fruit production, and overall energy transfer within the plant. Potassium helps regulate water uptake, improves disease resistance, and enhances plants’ overall health and vigor.

In summary, it can be stated that an oak tree needs a fertilizer with a high nitrogen content, so it is essential to look at the labels of fertilizers and understand the meaning of the numbers on the packages.

what kind of fertilizer for oak tree
What Kind of Fertilizer for Oak Tree? Opt for oak tree fertilizer spikes, which provide convenient and targeted nutrient delivery for strong and flourishing oak trees.

Best Oak Tree Fertilizer

As mentioned, a mature oak tree rarely needs fertilizer unless it has suffered from pests and diseases. Typically the oak tree gets its nutrients from the leaves that fall and decompose into organic matter. But young oaks need fertilization to become more established.

Before fertilizing any oak tree, measure the soil’s pH to ensure it has the correct pH. According to Pennsylvania State University, oak trees need the soil to have a pH between 4.5 and 7. With the proper pH, the oak tree will be better able to absorb nutrients and fully utilize the fertilizer.

I have tested and recommended several fertilizers for oak trees. I can tell you that the best fertilizer for oak trees is an NPK 15-5-10 fertilizer in spikes. Likewise, I prefer an oak fertilizer with a rich composition of nitrogen and potassium, such as an NPK 15-5-10 composition, and a solid fertilizer in spikes. Why should an oak fertilizer be rich in nitrogen and potassium? Because these are the two essential nutrients for a young oak tree or one suffering from a disease.

Also, oak fertilizer 15-5-10 contains iron, manganese, and sulfur, other minerals that oak trees need to grow and develop properly, especially in young oaks that need to establish themselves. Mature oaks rarely need fertilization unless they have suffered from a pest or disease that has damaged them badly.

If getting a 15-5-10 oak fertilizer is impossible, look for an alternative that always contains more nitrogen than the other nutrients. For example, you could use an NPK 16-4-4 fertilizer, another type of NPK fertilizer used on trees and shrubs.

Miracle-Gro Tree & Shrub Plant Food Spikes, 12 Spikes/Pack, 12 count (Pack of 1)
  • Promotes vibrant color and lush foliage
  • Contains natural ingredients
  • Feed once per season in Spring and Fall

When to Fertilize Oak Tree

The best time to fertilize oak trees is early spring, just before new growth begins. That makes the nutrients readily available when the tree starts growing. Fertilizing in early spring also helps promote strong root development and overall tree vitality.

It is essential to avoid fertilizing oak trees in late summer or fall. Fertilizing during this time can encourage late-season growth, making the tree more susceptible to winter damage. In addition, fertilizing oaks in late summer or fall can disrupt the natural hardening process necessary for the tree to prepare for winter dormancy.

I always recommend reading the fertilizer manufacturer’s instructions. Still, as a general rule, you should only fertilize oak trees in early spring.

when to fertilize oak tree
When to Fertilize Oak Tree? Mature oaks should be fertilized in early spring.

How to Fertilize Oak Tree

Each fertilizer has its instructions for use. Using a liquid fertilizer that requires dissolution in water differs from using a slow-dissolving granular fertilizer. The important thing is always to read the instructions of the fertilizer manufacturer. In the following paragraphs, I will explain how I use NPK 15-5-10 fertilizer on my oak trees.

Use the diameter of the drip irrigation line of your oak tree as a guide to determine the number of fertilizer spikes needed per plant. Suppose you do not use a drip irrigation system. In that case, you can measure the diameter like an irrigation system. Remember that these instructions are for an oak fertilizer with a composition NPK 15-5-10, like the one I use in my garden.

Drip Line DiameterNumber of Spikes
4 feet1 spike
6 feet3 spikes
8 feet5 spikes
10 feet7 spikes
12 feet10 spikes
15 feet16 spikes

The best time to apply spikes is in early spring when the soil is soft and moist. You can also spike after rain. Bury the fertilizer spikes 2 inches (5 cm) deep.

How Often to Fertilize Oak Tree

For mature oak trees, a single annual fertilizer application is usually sufficient. Apply a slow-release, balanced fertilizer with a nitrogen-phosphorus-potassium (N-P-K) ratio of 15-5-10 or 16-4-4. That will provide a steady supply of nutrients over an extended period.

Young oak trees, on the other hand, may benefit from two fertilizer applications per year. Apply the first round of fertilizer in early spring, as mentioned above. You can make the second application in early fall to support root growth and enhance winter hardiness.

Always follow the manufacturer’s instructions regarding the amount and method of application. Over-fertilization can harm oak trees, so using the correct amount is crucial, and avoiding applying fertilizer directly to the trunk is vital.

how often to fertilize oak tree
How Often to Fertilize Oak Tree? Fertilize mature oak trees once a year. Fertilize young oaks twice a year.

Final Conclusions

A mature oak tree will rarely need fertilizer. Still, it can benefit from nutrient application after it has suffered from a pest or disease. In addition, if you remove the leaves that fall from the oak tree, you will need to fertilize it because these are its natural nutrients.

On the other hand, fertilizing young oak trees will help them establish themselves more efficiently and have enough nutrients to resist pests and diseases that can affect a young oak tree. I hope this article will be helpful and that you can fertilize your oak tree correctly. If you have any questions, please do not hesitate to contact us through the contact form. I recommend you read our article on how to plant oak trees.

About Henry Morgan

Henry Morgan is an agronomist horticulture founder of The Garden Style Company and The Garden Style Website. He previously worked for Mondelēz International as an Agronomist Engineer specializing in agricultural products management in highly populated areas. In 2000, Henry started working with farmer-producers in agricultural businesses selling wholesale fresh produce and retail plants in Van Buren, Arkansas. Nowadays, Henry lives in California, where he offers expert consulting services for organic vegetable gardening. As a science writer working with his wife, Julia, Henry shares his passion for gardening and farming, trying to reach and teach as many folks as possible.

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