How Long Do Fertilizer Spikes Last? The Facts Explained

Fertilizer spikes are a handy tool for home gardeners. Spike form fertilizers are more expensive than granulated or liquid fertilizers but have the advantage of allowing a controlled release of nutrients. 

Fertilizer spikes typically last two months to a year, as they come in various formulations for different types of plants. Spikes formulated for potted and garden bedding plants tend to last for up to eight weeks, while spikes used for shrubs and trees can last six months to a year. 

In this article, I’ll explore what fertilizer spikes are, how to use them effectively, and how long they are good for. I will also examine the advantages and disadvantages of using fertilizer spikes, so read on!

Fertilizer Spikes Provide Slow-Release Plant Nutrition

Plant nutrition refers to the minerals and elements plants need to grow well.

These comprise the macronutrients, which are:

  • Nitrogen
  • Phosphorus
  • Potassium 

Other nutrients needed by plants can be categorized into secondary and micronutrients. 

Fertilizers are a way to add these nutrients to the soil after the soil has been depleted by plants. While fertilizers can be categorized in many different ways, we have to consider the different ways that fertilizer can be applied to the soil to understand fertilizer spikes.

Based on application, fertilizers can be categorized into:

  • Liquid
  • Solid pellets or granules
  • Spikes

Each of these types of fertilizers has its advantages. The primary advantage of using fertilizer spikes is that they are a slow-release fertilizer, one of the most efficient ways of supplying nitrogen and other macronutrients to the soil. 

Slow-release fertilizers ensure that the plant grows steadily instead of shooting up at the time of fertilizer application and slowing down afterward. Among inorganic fertilizers, fertilizer spikes are the most likely to be slow-release. 

Being slow-release means that fertilizer spikes can be used throughout the year, unlike other fertilizers that are not slow-release. Other fertilizers should only be applied before and during the growing season. 

Fertilizer spikes are also really easy to use as they can be simply placed into the soil around your plants, shrubs, or trees and left to do their job. This is much easier and quite unlike liquid fertilizers, which need to be applied carefully and pellets or granules that need to be incorporated into the soil to be effective.

Storage and Shelf Life

Fertilizers can be organic or inorganic, and in both cases, they need to be stored in a safe space to ensure that they maintain their effectiveness as you wait to use them. 

Fertilizer spikes do not expire so long as they are stored according to the manufacturer’s instructions. The minerals in fertilizers do not degrade, so you can use old fertilizer spikes for your plants. However, they must be stored correctly to remain effective, usually in a cool, dry place. 

Most fertilizers keep for a long time, only losing effectiveness with oxidation. Oxidation is a necessary process, as it allows the release of plant nutrients from the fertilizer into the soil. This means that some of the nutrients are lost over time. 

However, the elements used to make fertilizer spikes do not degrade, which is why they will not hurt your plants even if you use your old ones. They will simply not work as well as new ones. 

Effective Use: Step-by-Step Guide, Frequency, and Placement

Fertilizer spikes are among the easiest types of fertilizers to use. These spikes are usually formulated to suit the needs of your garden.

How to Use Spikes

Here are the steps to use fertilizer spikes effectively:

Choose the Right Ones for Your Plants

Choosing the right fertilizer spikes for your plants is very simple. All you need to do is identify the type of plants you have, then you can look for the corresponding fertilizer spikes and buy them. 

Determine How Many You Need

When deciding how many spikes to use, follow the directions on the packaging.

Typically, the number of spikes is determined by the height of the plants, so you would use one spike for about 3 feet (0.91 m) of height. You’ll probably need about 6 to 8 spikes along each foot (0.3 m) of the vegetable row for rows of vegetables. 

Insert Them Into the Ground

Fertilizer spikes are designed to be hammered into the ground. You can also dig holes in the garden around your plants if you need to and place your spikes in these holes. 

Fertilize According to the Season

While you can use fertilizer spikes throughout the year, they are most effective in your garden’s growing season. Be aware of when this is, especially for grass and cool weather grass that starts growing in the fall.

Houseplants can be fertilized throughout the year, but trees and shrubs do well with an additional boost of nutrition around spring

You Don’t Need to Water Them First

An important thing to remember is that while wetting the ground will make it easier for you to drive your spikes into the ground, it doesn’t encourage the release of nutrients.

As fertilizer spikes are slow-release fertilizers, nitrogen and other macronutrients are released as a result of microbial activity rather than water. 

Recommended Frequency

Fertilizer spikes don’t need to be used as often as other types of fertilizers as they are concentrated spikes of plant food. How often you use the spikes will depend on your plant and the seasons. 

Refer to the following considerations below:

  • Install fertilizer spikes every month for plants and shrubs in the growing season and every 2 months through the rest of the year.
  • Trees need less fertilizer, so you can use the spikes every 3 to 6 months. Use the spikes more often in the growing season and then reduce the frequency. 
  • Houseplants can be fertilized all year round, especially tropical plants, so you can use the spikes as often as required by the plants to ensure consistent growth. 

The primary advantage of fertilizer spikes is that their slow-release nature ensures that your plants will not be burned because they received too much fertilizer. However, you still need to be careful and ensure that you’re only using the recommended number of spikes per plant. 

Consistent and healthy plant growth takes time. If you overdo the number of fertilizer spikes to help your plant grow faster, you might cause the plant to shoot up with weak stems or, worse, dry the plant out due to ‘burning.’

Proper Placement

Fertilizer spikes are designed to be placed into the ground around your plants or along your vegetable rows. 

You can hammer your fertilizer into the ground or dig holes to place them in. The spikes should be about halfway between the stem of the plant and the rim of your pot. For shrubs and trees, the spikes should be about 2 feet (0.61 m) away from the center of the plant and 3 feet (0.9 m) apart from each other. 

If you’re digging holes into the ground, you can make it easier for yourself by wetting the ground first. The wet ground will be more yielding, and you can make the right-sized holes for your fertilizer spikes. 

When measuring the distance from the plant for thicker stems and trunks like shrubs and trees, it is important to calculate the distance from the center of the stem or trunk. This ensures that your spikes are away from the main trunk and able to release nutrients near the finer root hairs, which increase the surface area and absorption capabilities of your plants. 

Benefits and Limitations

Fertilizer spikes are a great way of giving your plants much-needed nutrition, but they have their limitations as well.

Here are the advantages and disadvantages of using fertilizer spikes:


  • Slow-release fertilizers: Being a slow-release fertilizer means that the spikes ensure even and consistent growth in the plant over an extended period of time.
  • Last a long time: Fertilizer spikes last longer than other fertilizer types, so you don’t have to use fertilizer as often, and you can store them for a long time. 
  • Improve soil health over time: As these fertilizers are broken down with microbial activity, they support the microorganisms in the soil, which improves overall soil health. 
  • Reduce the risk of over-fertilization: As the fertilizer is slow-release, the nutrients are released slowly without risk of burning. 
  • Compact and easy to store: The fertilizer spikes are compressed and can be stored easily in a small space. 


  • More expensive: While they are easy to store and use, they are more expensive for these very same reasons. 
  • Fertilizer release is too targeted: The fertilizer release can be concentrated in a small area where the spikes are planted. This means that the fertilizer may not penetrate as deep as it needs to or spread widely. The plant may then focus root growth only in areas where the spikes have been added. 

Final Thoughts

Fertilizer spikes can feed your plants for two months up to a year, depending on the type of plant and what season it is. Plants need fertilizer more often during the growing season, and fertilizer spikes are one of the easiest ways to supply nutrition to your plants. When stored correctly, the spikes can last forever, but they will become less effective over time. 

Alexander Picot

Alexander Picot is the founder of and its lead content writer. He created the website in 2022 as a resource for horticulture lovers and beginners alike, compiling all the gardening tips he discovered over the years. Alex has a passion for caring for plants, turning backyards into feel-good places, and sharing his knowledge with the rest of the world.

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