How Many Fertilizer Spikes Do You Need per Tree?

Fertilizer spikes are one of the most convenient ways of fertilizing your plants and supplying them with much-needed nutrition. They’re compressed spikes of plant nutrients that can be placed in the soil around your plants. 

You need one fertilizer spike for every two inches of the tree’s diameter. However, you can also decide by looking at the dripline. When going off the dripline, you should place the spikes along the line, keeping three feet (0.91 meters) of space between each spike.

In this article, I’ll explore how you can use fertilizer spikes for trees. I’ll also look into the do’s and don’ts of fertilizing trees so you can decide how to use your fertilizer spikes, so read on!

Using Fertilizer Spikes for Trees

Fertilizer spikes are an easy and effective way of adding nutrition to plants, shrubs, and trees. Fertilizer spikes are easy to work with and offer nutrition directly to the roots of the plants to maximize nutrient absorption. 

When it comes to trees, fertilizer spikes can be used to feed the trees for anything between six months to a year, depending on the tree’s needs. 

Additionally, fertilizer spikes for trees tend to last longer than spikes for plants and shrubs as trees need less feeding than young plants or shrubs.

Fertilizer spikes are effective for most trees, though they may not be the best idea for fruit trees. Spikes are compressed plant nutrition, so even though they’re slow-release fertilizers, they may release nutrition in a concentrated area, causing uneven root development. 

Nevertheless, spikes can be an easy way of fertilizing trees and keeping them fed over a long time. To use your fertilizer spikes for your trees, you need to follow a few simple steps. 

  1. Find the right formula: Finding the right formula is essential to ensure that your trees are receiving the right nutrients in the right quantity. There are a number of different nutrients that plants need, and each plant or tree will have different needs. Fertilizer spikes are formulated according to the specific needs of different types of trees, so ensure that you’ve picked the right formula for your trees. 
  2. Measure the diameter of your tree or identify the drip line: To identify how many fertilizer spikes you need, you should measure your tree’s drip line or diameter. Based on these measurements, you can decide exactly how many spikes you need. To identify the drip line, you can measure about two feet out from the center of the tree’s trunk. To calculate the diameter of the tree, you should use a caliper. 
  3. Calculate the number of spikes you need: Based on the drip line or diameter of the tree, you can determine how many spikes you need. Calculate how many spikes you’ll need to place along the drip line with three feet (0.91 m) between each spike. You can also use one spike for every two inches of the tree’s diameter as measured on the caliper. 
  4. Hammer the spikes into the ground around your trees: Once you’ve identified the formula and determined how many spikes you need, you should read the package instructions. Then take the spikes, place the cap on top, and hammer them into the ground around your trees. 

Additionally, you can dig holes for your fertilizer spikes if you find that easier. Wetting the ground before you dig will make it easier to dig. 

When Should I Fertilize My Tree With Fertilizer Spikes?

Fertilizer spikes can be used year-round for most plants, but trees don’t need as much nutrition. One spike can last as long as a year for trees, but it’s important to feed your trees at the right time. 

Fertilize your tree with fertilizer spikes in early spring, just before the growing season. If your spikes last six months, you can add additional fertilizer spikes in late fall to help your tree outlast winter. Be careful not to add too many spikes, and follow the instructions on the package. 

Young trees especially benefit from an additional infusion of nutrients in late fall. Young trees haven’t developed the hardiness of mature trees and need all the help and nutrients they can get to outlast the winter. 

Early spring and late fall are also when the ground is wet and more malleable, which makes it easier to put the spikes into the ground. 

For the most part, you’ll be best served by following the instructions on the packaging of your fertilizer spikes. Assuming that you’ve chosen the right kind of fertilizer spikes for your trees, the packaging will support you with clear instructions about when you should use the spikes for the trees. 

Can You Break Up Fertilizer Spikes?

While fertilizer spikes are convenient and a slow-release fertilizer that won’t burn your plants, they do have some disadvantages. The primary disadvantage of fertilizer spikes is that the nutrition can become concentrated in a small area of the tree’s roots. 

You can break up fertilizer spikes. If you want to use your fertilizer spikes as broadcast fertilizers, crumble the fertilizer spikes and spread them around your tree. If you want to ensure that the nutrition still reaches the roots easily, wet the ground and press the pieces into the ground.

Broadcast fertilizers are fertilizers that are spread across the surface of the soil that needs to be amended with additional nutrition.

Broadcast incorporated refers to the method by which these fertilizers are incorporated into the soil. 

To use your fertilizer spikes in this way, you should still calculate the right number of spikes needed based on the drip line or the diameter of your tree. Then you can crumble the spikes and broadcast them under the canopy of your tree. 

An important thing to remember when using fertilizer spikes as broadcast fertilizer is to keep the fertilizer at least two feet (0.61 m) away from the center of the trunk. The distance ensures that any pests or insects don’t have a direct line to attack the trunk and that the fertilizer doesn’t burn any important roots. 

The Do’s and Don’ts of Fertilizing Trees

Here are the dos and don’ts of fertilizing trees so you can use your fertilizer spikes effectively. 


  • Get a soil analysis done to understand what amendments the soil needs.
  • Ensure that the fertilizer won’t upset the pH value of the soil.
  • Choose a fertilizer that’s at least 50% slow-release.
  • Check for and avoid fertilizers with formaldehyde and salt.
  • Make sure the nitrogen, phosphorus, and potassium ratio is appropriate for your trees.


  • Over-fertilize your trees by using too much fertilizer.
  • Fertilize too close to the roots. 
  • Use too much fertilizer before winter.
  • Apply the fertilizer unevenly. 
  • Use nitrogen-rich fertilizer for young trees.

Following these do’s and don’ts will ensure that your trees stay healthy and don’t get overwhelmed with nutrition whether you’re using fertilizer spikes, granules, or liquid fertilizer.

Should You Fertilize Trees?

Trees typically need less nutrition than plants or shrubs as they grow slowly and supply much of their own fertilizer through the mulch. However, this doesn’t mean that trees don’t need fertilizer. 

You should fertilize trees to keep them healthy and allow them to maintain healthy foliage. Supplying additional nutrients to trees through fertilizer helps trees develop and maintain a resistance to pests and disease, which helps them live longer. 

Typically trees prefer nitrogen-rich fertilizers, but young trees that are fed too much nitrogen will grow more leaves instead of roots, which will impact their longevity and resistance to drought. 

Phosphorus is the macronutrient responsible for encouraging root development, and it’s a good idea to have a higher percentage of it in fertilizers for young trees. Potassium is related to water intake, and fertilizers rich in potassium and phosphorus are ideal for fruit trees.

However, the majority of mature trees prefer nitrogen-heavy fertilizers, and the older a tree gets, the less likely it is that it will need supplementation of potassium or phosphorus. 

A good way to tell if trees need fertilizer is by checking for growth, discolored leaves, dead spots, and falling leaves. One or all of these signs present usually indicate a tree that needs nutrition. 

Young trees can be fertilized once or twice a year, while older trees only need nutrition annually or once every two or three years. 

How Long Does It Take for Fertilizers To Work on Trees?

When applied to plants and shrubs, fertilizers tend to show a quick effect. Plants are particularly sensitive to fertilizers and show improvement within a few days. But trees are different. 

Fertilizers applied to trees can take several months to work. The effects of the fertilizers can be seen in about 3 to 4 months, depending on the age of the tree and the amount of water available in the soil. Older trees may take longer to show any changes due to fertilizer applications. 

Fertilizer spikes tend to work more slowly than other types of fertilizers as they’re slow-release. However, they are more effective and will show in the improved vigor and health of the foliage and branches of the tree after a few months have passed. 

Final Thoughts

To calculate the number of fertilizer spikes you need for your tree, you need to measure the diameter of the trunk using a caliper or check the dripline of your tree. 

You can use about one spike for every two inches of the tree trunk’s diameter, or you can use as many spikes as you can fit along the tree’s drip line when spaced with three feet (0.91 m) between each spike. When in doubt, follow the instructions on the packaging.

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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