Are Fertilizer Spikes Good? All Pros and Cons

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There’s a lot of debate around the use of fertilizer spikes. Some gardeners swear by them, while others say they’re not worth the money. So, what’s the verdict? Are spikes good or bad for your plants?

Fertilizer spikes are good because they gradually release nutrients into the soil as triggered by bacterial and fungal activities. This way, you can’t burn your plants due to over-fertilization. However, fertilizer spikes have downsides, including a lack of control over the nutrients released.

In this article, I’ll discuss how fertilizer spikes work, including their pros and cons. You’ll also learn how to use fertilizer spikes for the best results. Keep reading for more tips about using fertilizer spikes safely.

How Do Fertilizer Spikes Work?

Fertilizer spikes work by releasing nutrients into the soil gradually to be used by plants. The spikes contain slow-release fertilizer encased in a polymer. This polymer breaks down gradually, releasing the encased nutrients into the soil.

The rate at which the spikes release fertilizer depends on the type of polymer used and the soil moisture content.

According to Agriculture Journals, high water content in the soil triggers more fungal and bacterial activities. In turn, these activities break down the fertilizer polymer more quickly, releasing nutrients into the soil faster. Conversely, low water content in the soil results in a slower breakdown of the polymer, thus, a slow release of nutrients.

The Pros of Fertilizer Spikes

Photo 210094912 | Fertilizer © Chernetskaya |

Fertilizer spikes provide a steady and gradual release of nutrients into the soil. This continuous release is unlike liquid and granular fertilizers that you must apply more frequently. Based on their mode of operation, fertilizer spikes have the following pros:

Easy to Use

Unlike granular and liquid fertilizers, you don’t have to worry about over or under-fertilizing your plants when using fertilizer spikes. This benefit of using spikes is because the manufacturer determines the amount of nutrients released into the soil.

Fertilizer spikes are easy to insert into the soil, and you can do it without digging a hole. You simply push the spike into the soil.

According to NC State University, improper mixing of fertilizers leads to excessive nitrogen in the soil, which causes fertilizer burn. However, using fertilizer spikes that don’t require mixing eliminates this concern.

Ideal for Busy Gardeners

If you’re a busy gardener with little time to spare, fertilizer spikes are a good option. One of the main benefits of spikes is that you only need to apply them twice a year, in mid-fall and early spring. However, you can replace the spikes every three months (90 days) for the best results.

Granular and liquid fertilizers, on the other hand, need to be applied frequently. According to the University of Florida, you’ll have to use regular fertilizer every three to four weeks for the best results. This constant requirement means you must make more trips to the store and spend more time (and money) on fertilizer.

High Degree of Precision

With fertilizer spikes, you can place nutrients exactly where they’re needed; at the root zone. You don’t waste nutrients by applying them to areas where they’re not required. In the long run, you save money that you would have used to buy more fertilizer for extra nutrients.

They Prevent Fertilization Burn

Fertilization burn results from placing too much fertilizer around a plant. This issue is more common with granular and liquid fertilizers on the soil’s surface.

Fertilization burn can damage your plant’s roots, leaves, and stems. In severe cases, it can even kill your plants. However, fertilizer spikes eliminate this problem since you place them underground, away from the plant’s leaves and stems.

Some signs of fertilization burn on plants include:

  • Yellow or brown leaves
  • Wilting leaves
  • Leaves that curl up or droop
  • Stunted growth.

If you notice any of these signs on your plants, it’s a good idea to stop using fertilizer and wait for the symptoms to disappear. You can then start using fertilizer again but in smaller amounts.

Stimulation of Biological Activities in the Soil

Fertilizer spikes stimulate biological activity in the soil, which is beneficial to your plants. This activity arises because the spikes provide a slow and steady release of nutrients into the soil, stimulating nitrifying and denitrifying microorganisms.

ResearchGate discusses that these microorganisms help improve the soil quality by breaking down organic matter and releasing nutrients essential for plants.

Eliminates Leaching

Leaching is how water moves nutrients through the soil and eventually drains them away. This draining is a problem with granular and liquid fertilizers when applying them to the soil’s surface.

You situate fertilizer spikes under the ground where they’re not affected by leaching. Thus, more nutrients stay in the soil where they’re needed.

The Cons of Fertilizer Spikes

As with anything that has pros, there are also cons. The main cons of fertilizer spikes include:

Lack of Control Over the Release of Nutrients

With fertilizer spikes, you have no control over the release of nutrients into the soil. The manufacturer determines the amount of nutrients released after considering your soil’s conditions like moisture and fertility.

At some point, you may notice that your plants need more or less of a given nutrient released by the fertilizer spike. In this case, you have nothing much to do as the spikes will continue releasing the nutrients as was initially set. You can only return to the manufacturer with new requirements for a different spike.

With granular fertilizers, It’s easy to vary the amount of nutrients you apply to your plants. As a result, you have more control over the nutrients your plants receive.

Incomplete Coverage

Fertilizer spikes only release nutrients to the area around them. If you spread your plants out, you’ll need multiple fertilizer spikes to cover all of them. What does this mean to you as a gardener? More money and time spent on placing the spikes.

It’s also possible to miss some areas while placing the fertilizer spikes. Missing some plants can result in uneven growth.

Challenging To Apply in Some Areas

Fertilizer spikes can be difficult to apply in some areas like potted plants. This application can be tricky because you need space to dig a hole, place the fertilizer spike, and then cover it with soil.

You must be cautious when digging the hole to avoid breaking your pot. Therefore, placing the spikes is not as easy as scattering granular fertilizer around the plant.


You risk over-fertilizing your plants if you do not appropriately place the spikes. If you put the spikes close to the tree trunk, the roots will be over-fertilized, leading to problems like wilting.

Following the manufacturer’s instructions when applying fertilizer spikes is essential to avoid over or under-fertilizing your plants.

Fertilizer Spikes Are Expensive

Manufacturers design spikes to deliver nutrients per measured area or plant type for efficiency. Therefore, you buy the spikes depending on the number and type of plant.

You’ll have to buy many spikes if you have large plantations. Buying many spikes translates to more money than granulated fertilizer that can top-dress over a large area.

Are Fertilizer Spikes Good for Any Type of Plant?

Fertilizer spikes are good for any type of plant. Manufacturers formulate these spikes to provide essential nutrients to different plants. Furthermore, spikes are pre-measured to eliminate the chances of over-fertilizing your houseplant, shrub, or garden.

The specific requirements of your plants should determine the type of fertilizer spike you buy. For example, if you’re growing roses, rose fertilizer spikes will provide the proper nutrients for optimal growth.

Factors To Consider Before Buying Fertilizer Spikes

Although fertilizer spikes are suitable for any plant, you must get the right one. Consider the following factors when looking for fertilizer spikes:

The Type of Plant

What plants do you have in your garden? Are they annuals, perennials, vegetables, fruits, or roses?

The plant you’re growing will determine the specific fertilizer spikes you buy. Different plants have different nutrient requirements.

For example, roses require more nitrogen for leaf growth, while vegetables need more phosphorus for root development.

The Nutrient Content

When buying fertilizer spikes, check the nutrient content to ensure that the spikes have all the nutrients your plants need.

The package label will indicate the fertilizer grade and the percentage of each primary macronutrient by weight.

The fertilizer grade is the total amount of nitrogen, phosphorus, and potassium in a given fertilizer. The North Carolina Department of Agriculture and Consumer Services recommends soil testing to determine how much of each nutrient your farm needs.

The Application Rate

How fast do you want the nutrient released to your plants? For efficacy, the spikes tend to release nutrients slower than granular types. Although this protects your plants from bur or overfertilization, it prevents you from delivering a high nutrient load to your plants if you require it.

Fertilizer spikes are slow-release in nature. The spikes slowly release nutrients into the soil over time. Therefore, they may not be an option if you’re looking for fast-acting fertilizer.

How Long Do Fertilizer Spikes Last?

Fertilizer spikes last for about three to four months. However, this depends on the type of fertilizer spike, climate, and specific plant requirements. For efficiency, it’s advisable to change your spikes every three months (90) days.

Are Fertilizer Spikes More Effective Than Other Methods?

Fertilizer spikes are more effective than other methods because they are pre-measured. You’re less likely to over-fertilize your crops which may lead to fertilization burn. 

Other reasons why fertilizer spikes are more effective than granulated or liquid-based fertilizers are:

  • They’re less likely to be washed away by rain or irrigation.
  • They don’t require a frequent application like granular fertilizer.
  • They’re less likely to be blown away by the wind.

How To Use Fertilizer Spikes

The efficiency of your fertilizer spikes will depend on how accurately you use them. If you’re using them for the first time, here’s a guide to help you get started:

Choose the Right Spike

You must buy the right fertilizer spike depending on your plants’ requirements.

For example, if you’re growing roses, get rose fertilizer spikes. The same applies to other plants such as vegetables, fruits, annuals, and perennials.

Insert the Spikes Into the Soil

After getting the suitable fertilizer spikes, it’s time to insert them into the soil. The number of spikes you’ll use will depend on the size of your plants.

You should use two spikes per tree if their trunks have a diameter of one to two inches. On the other hand, use one spike for every three feet of a shrub’s height. You’ll need a tape measure to take these measurements.

Proceed to insert the spikes after knowing how many you’ll use per tree. Here is the procedure:

  • Dig a hole that’s as deep as the fertilizer spike. You can use a tape measure to measure the spike and ascertain the exact length of the hole.
  • Insert the spikes into the soil around the drip line.
  • Space out the fertilizer spikes according to their label recommendations. For example, if the package recommends 12 inches between each spike, maintain this distance when placing them in your garden.
  • Cover the fertilizer spikes with soil to prevent direct sunlight, which may distort the nutrients.

Final Thoughts

Fertilizer spikes are suitable for use on any type of plant. These spikes offer a convenient and mess-free way of fertilizing your garden. The spikes eliminate nutrient loss through leaching by being placed into the soil.

If you have challenges with fertilization burn, spikes are your best solution. The spikes are pre-measured, and you can space them out to avoid over-fertilization.

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