Can Fertilizer Spikes Kill Trees?

Fertilizer spikes are quick and convenient to use, but are they safe for your trees? Know the advantages and drawbacks of using fertilizer spikes and the right way to apply them.

Sean Stratton | Updated March 8, 2023
fertilizer spikes

Fertilizer spikes are the easiest way to fertilize trees. You can simply push the spikes into the soil based on your tree’s fertilizer requirements and enjoy faster growth and healthier trees.

But is this “easy way” good for your trees? Are there any side effects of fertilizer spikes? And most importantly, can fertilizer spikes kill trees? Let’s find out.

Can Fertilizer Spikes Kill Trees?

Fertilizer spikes are meant to benefit trees, but they can also cause serious harm. They contain concentrated nutrients and fail to distribute them evenly.

Too many fertilizer spikes can kill trees if placed too close to the trunk due to excessive nutrients, leading to over-fertilization.

Over-fertilization can cause the following problems:

  • High salt concentrations can dry out the roots.
  • Damage to the tree’s roots makes it harder to absorb water and nutrients from the soil.
  • Fungal growth can cause root rot.
  • Leaf burn from excessive nitrogen

Are Fertilizer Spikes Good for Trees?

With the accurate calculation of the fertilizer needs of your tree and proper application, fertilizer spikes can benefit your trees. But according to many gardeners, there are many downsides to using these spikes on trees. But let’s put the drawbacks aside and talk about the advantages first.

Firstly, if you choose a good slow-release fertilizer spike, it will feed your tree for a long time. This will save you from frequent fertilizer application. So, you will get a little extra time to take a deep breath and enjoy the beauty of your garden.

Secondly, if you have a garden with lots of trees, fertilizing can be time-consuming, troublesome, and messy work. But if you use fertilizer spikes, you can fertilize a large area with comparatively less hassle.

Thirdly, some fertilizer may smell pretty bad. If you use a stinky fertilizer, no wonder your garden will smell like a nightmare! So, when you are using these small fertilizer spikes there are no chances of dealing with odor after applying. Even if the spikes contain some odor, you are going to push them down into the soil, so you don’t have to worry about odor after applying.

Also read: Can You Use Fungicide and Fertilizer at the Same Time?

Now coming to some downsides, if you use granular or liquid fertilizers properly, you will be able to distribute the nutrients to the plants evenly. But when it comes to fertilizer spikes, these are designed to be hammered into the soil. And this design allows them to release the nutrients in a way that the nutrients may not reach the roots that are in the deep soil.

Also, if you are unable to correctly measure the fertilizer needs of your tree, you will not get better results. So, the accurate calculation of nutrition requirements and proper application will decide whether or not the fertilizer spikes will be a good choice for your trees.

Can You Use Fertilizer Spikes on New Trees?

Some people use fertilizer spikes on their young trees and claim that they got positive results. However, if you are thinking of applying fertilizer spikes to your young trees you need to be very careful while applying because you don’t want to burn your trees.

While some people are talking about success, a few individuals reported negative results, so applying spikes on young trees means you are leaving your trees vulnerable to some risks.

That’s why if you are determined to give it a try with fertilizer spikes, measure the needs of your trees carefully, place the fertilizer spikes in the right place, and hope for the best.

How Many Fertilizer Spikes Do You Need for a Tree?

After calculating the fertilizer needs of your tree, I guess the first thing you will need to know is how many fertilizer spikes you need for a single tree.

If you are using a fertilizer like Jobe’s fertilizer spikes and the diameter of the trunk of your tree is one to two inches, use 2 spikes only. For trees with more diameter stick to the instructions provided by the fertilizer spikes manufacturer.

And if you choose other brands and their instructions are different from Jobe’s, I would suggest you follow the manufacturer’s instructions for your product. No matter which brand you choose, always make sure you place the fertilizer spikes along the dripline of your tree. Never place the fertilizer spikes too close to the trunk.

One more thing, in case you want to fertilize your shrubs with fertilizer spikes, let me tell you how many spikes you need. For a shrub that has a height of 3 feet, use only one Jobe’s fertilizer spike. For a shrub that has a height of 6 feet, use two Jobe’s fertilizer spikes. If the height is more, increase the number of fertilizer spikes accordingly.

Here is the Jobe’s Fertilizer Spike (Check Price and Reviews).

Applying Fertilizer Spikes too Close: Good or Bad

Applying the fertilizer spikes too close to the tree trunk is a pretty bad idea. You should never place the spikes close to the tree trunk. The ideal distance to place fertilizer spikes is to place them along the dripline.

If you don’t know what a dripline is, let me help you with that. Dripline is the area in the ground that is located right under the outermost circumference of the canopy of a tree. This is where excess water drips from when the canopy gets wet.

The term Critical Root Zone (CRZ) or Root Protection Zone (RPZ) of a tree also refers to this drip line; they all mean the same thing.

If you are using fertilizer spikes for shrubs, measure a distance of about four to five inches from the stem of the shrub. This is the ideal distance to place your fertilizer spike.

Can You Break Up Fertilizer Spikes?

Yes, you can break up a fertilizer spike while hammering it into the soil. However, you should place the spike very carefully. If you strike a wooden spike in the soil and make a hole first, you can easily insert the fertilizer spike afterward. This will reduce the chances of breaking the fertilizer spike.

How Long Does Fertilizer Spike Last?

This will depend on which brand you are choosing. If you choose a slow-release fertilizer spike from a renowned brand it can last a long time. For example, Jobe’s says that their slow-release fertilizer spike will last all season. So, if you are thinking of ordering online, you can check how long the spike will last in the information section of the product.

Final Thoughts

Besides some downsides, fertilizer spikes have many benefits as well. If you manage to use the spikes properly by measuring the needs of your tree, you can expect better results. So, if you want to try an easy way of fertilizing your trees, you can go ahead with fertilizer spikes and see how things work.

But before you apply the fertilizer, make sure to calculate the fertilizer requirements of your tree, and then choose fertilizer spikes with a proper NPK ratio. After that, measure the ideal zone for placing the spikes which is the dripline area, and finally, you are ready to push some fertilizer spikes into the soil.

Written by Sean Stratton

Sean Stratton

Hi, I'm Sean, the senior editor here at Fertilizer Pick. I grew up on a farm in North Carolina and have grown fruits, vegetables, and trees since childhood. While I no longer live on a farm today, I still enjoy spending time on my garden and sharing my knowledge with friends and fellow garden enthusiasts.