What is 18-18-18 Fertilizer Used For? | Best Guide

You will love this in-depth guide if you want to know what 18-18-18 fertilizer is used for.

Now you might be wondering, what does this number show?

This number is the NPK ratio. Simply put, it tells the percentage of 3 elements in the fertilizer. These three elements are Nitrogen, Phosphorus and Potassium.

So here’s what the triple 18 fertilizer contains:

  • Nitrogen: 18%
  • Phosphorus: 18%
  • Potassium: 18%

And other nutrients as well.

Before talking about this fertilizer, let me introduce these nutrients to you.

What Does “18-18-18” Mean?

As I mentioned above, this number shows the percentage of nitrogen (N), phosphorus (P), and potassium (K).

You must remember three words to remember NPK.

Up, Down, and All-around

Here’s how high nitrogen in this fertilizer is useful.


Nitrogen is an essential nutrient for plant growth.

Here’s why.

Nitrogen is the go-to nutrient for powering any leaf, stem, and foliage growth.

Hence this represents the word up.

Now let me tell you how a plant absorbs Nitrogen.

Note that a plant cannot take up Nitrogen directly from the soil. It is obtained when ammonia is added to the soil, and the plant takes nitrogen from NH₄⁺ and NO₃⁻ ions.

18-18-18 fertilizer

Nitrogen is also a major component of chlorophyll.

Now, what is chlorophyll?

This green pigment inside the leaf of a plant is necessary for photosynthesis. It absorbs sunlight and produces food (glucose) using water and carbon dioxide.


Nitrogen is the go-to nutrient for healthy, vibrant leaves and supports essential functions like photosynthesis.


When it comes to phosphorus, it powers fruiting and blooms.

The other primary function of phosphorus is supporting plants’ shoot and root systems. Thanks to phosphorus that our plants anchor firmly in the soil.

This nutrient is essential in the average growth and metabolism of plants.

Now you might be wondering, how does a plant obtain phosphorus?

A plant takes up phosphorus in its primary forms. These are called orthophosphates, H2PO4 and HPO42-.

Note: The plant usually takes phosphorus when the soil pH is less than 7.0.

As it majority supports the roots, it represents the word down.

Now, let’s summarize all this.

Phosphorus powers blooms and fruiting. The right amount of phosphorus means an improved root system, beautiful flowers, and healthy fruits.

Now let me introduce potassium to you.


As I mentioned above, this fertilizer has 18% potassium. Here’s why it is essential.

Potassium regulates the function of enzymes and controls the flow of liquids.

That’s why I say that potassium works “all-around”.

It is used for the growth and development of the plant.

It also activates the enzymes that make ATP, starch, and proteins. Note that enzymes are biological catalysts that speed up a reaction.

You should know that it also regulates the opening and closing of stomata.

Potassium is the key to conserving moisture, leading to increased drought resistance. Therefore, potassium deficiency will make your plants vulnerable to diseases.

That’s not what we want.

Potassium increases plants’ resistance to diseases. It improves the plant’s overall health by making them strong and vibrant.

Now let’s jump straight to our next topic.

What is 18-18-18 Fertilizer Used For?

Many plants love this balanced fertilizer.

Let’s take a look at a few of them.

Plants That Like 18-18-18 Fertilizer:

The balanced 18-18-18 fertilizer is a good blend for trees, tomatoes, container plants, and leafy vegetables. This is because it provides all three vital macronutrients (NPK) which support the growth and development of the plants.

Plants That Like 18-18-18  Fertilizer

Heavy feeding plants:

Tomatoes and peppers are some standard heavy feeders which need a lot of nutrients to grow.

These plants need a balanced for healthy foliage and fruit development.

18-18-18 fertilizer should be used during the growing season to help generate better blooms and more fruit.

The high amount of nitrogen and potassium will generate better fruit in terms of quality and quantity.

If your soil is deficient in a specific nutrient, it’s better to get personalized recommendations.

A soil test can find this.

Leafy Greens:

Lettuce, spinach, and kale are leafy vegetables that need plenty of nitrogen to grow.

18-18-18 Fertilizer contains high nitrogen and other nutrients that leafy plants need.

Nutrients like potassium and phosphorus are also essential for these plants, which this fertilizer provides in bulk quantities.

Plus, the high nitrogen content is what will produce dark green leaves.

If your soil is already high in nutrients, use a lighter blend or dilute 18-18-18 to its half consistency.


Trees & Shrubs:

Trees and shrubs generally like a balanced fertilizer.

The 18-18-18 provides all the macronutrients in bulk quantity and is great for growth.

This fertilizer helps leaf and root development in trees and preserves overall health.

If your soil is already high in nutrients, balanced 10-10-10 fertilizer would be a great choice.


Container Plants:

Container plants grow efficiently with a slow-release fertilizer during the planting and developing stage.

18-18-18 fertilizer will provide all the essential nutrients to your plant, leading to rapid growth.

This fertilization should be enough for the plant due to the stronger fertilizer blend.

For the best application rates, follow the instructions on the package.

The high potassium and nitrogen will boost the plants’ growth and generate vibrant green leaves.

This takes us straight to our next point.

You May Like:

20-20-20 Fertilizer | Is it The Best Balanced Fertilizer?

General Uses:

Here are some of the benefits of using this fertilizer:

  • It is water-soluble.

Being a water-soluble fertilizer, it releases its nutrients instantaneously after application.

This the precisely what most plants need, and their growth boosts.

Plus, its nutrient levels are not affected by leaching and erosion.

what is 18-18-18 fertilizer used for?

The best part is that the nutrients are readily available for plant absorption. Plus, they are easy to apply through fertigation.

Note: Fertigation is a process in which the fertilizer is included within the irrigation water.

  • The macronutrients present lead to healthy plant growth.

For your reference, let me tell you that Nitrogen (N), Phosphorus (P), and Potassium (K) are macronutrients.

As we discussed earlier, these macronutrients are essential in different ways. Here are some of them.

These nutrients provide energy to the plant to make food. Plus, they develop the root and shoot of the plant.

These nutrients are also involved in making chlorophyll, amino acids, proteins, and other substances. If you apply it correctly, it can enhance the beauty and greenery of your lawn.

Over here, I want to talk about Sulfur as well.


Sulfur is a macro element in plant nutrition. Here’s why it is essential.

A Plant makes amino acids, oils, and proteins by using sulfur. Moreover, it is used to form chlorophyll. And it can also activate many vitamins and enzymes.

The best part is that the 18-18-18 fertilizer has this nutrient in a bulk quantity.

If I talk about its application, only 10 to 30 pounds of sulfur per acre is used by plants. You can increase the soil acidity by adding elemental sulfur.

Pretty simple.

  • It leads to optimum photosynthesis as it encourages vibrant foliage.

Let me explain.

Foliage refers to the leafy part of your plant or tree. Over here, note that the main function of a leaf is to produce food by photosynthesis.

Further reading:

When To Fertilize Your Lawn in Florida? | The Ultimate Guide

7 Great Uses of DAP Fertilizer

Urea Fertilizer | 5 Amazing Uses

As I mentioned above, it also supports fruit and flower production. Due to increased nutrient availability, the plants’ tolerance toward pests may also increase.

  • Since it is a balanced fertilizer, it can be a good fit for indoor and outdoor plants.

Indoor and outdoor plants usually need multiple macronutrients. So when the triple 18 fertilizer is added to poor soil, it can provide even nutrient availability.

This promotes healthy growth. Notable.

Summary: If we talk about the uses of 18-18-18 fertilizer, it is water-soluble. As a result, leaching and erosion do not affect the nutrient levels. Plus, it is a balanced fertilizer and encourages vibrant foliage.

How and When To Use Triple 18 Fertilizer?

When watering, you can apply the 18-18-18 fertilizer by spreading slow-release granules or as a liquid. In some cases, fertilizer spikes can be effective as well.

how to use 18-18-18 fertilizer

Spikes release nutrients in the soil gradually.

Before planting a new sapling in poor soil, add some granules of the triple 18 fertilizer. This will lead to a fast establishment of your plant.

After plantation, you can also apply a water-soluble option. Over here, let me introduce water-soluble powder to you.

You can dilute powder fertilizers with water. At the time of plantation, they can lead to good growth as they are instantly available for uptake.

For vegetables, you can have better options as well. But if you apply 18-18-18 fertilizer after transplantation, you can also get a good outcome.

Can I use 18-18-18 Fertilizer For Citrus or Lemon Trees?

Quick answer: Yes, you can. But there are better options as well.

Lemon trees generally need a slow-release balanced fertilizer.

This is the reason why Nitrogen-rich fertilizers can work best for them. Let me explain.

The triple 18 fertilizer is a stronger mix. Therefore, an 8-8-8 fertilizer can work best for a lemon tree.

Talking about its application, here’s what you need to know:

  • You should apply the fertilizer throughout the growing season. If you are using a liquid fertilizer, then apply weekly.
  • For the amount of fertilizer, follow the package instructions carefully.

This is because the amount will depend on the size and age of your tree.

  • Nitrogen applications should continue throughout the year.
  • It should not be applied in winter when the tree is not growing.

Now, let me tell you how to use the fertilizer properly.

Before adding fertilizer to your lemon tree, read the instructions on the package carefully.

If it says “water-soluble“, then dissolve your fertilizer in water first. Then apply the fertilizer to the leaves when the soil is soaked above the root zone.

If you use a granular fertilizer, spread the fertilizer evenly by hand. You can also use a fertilizer spreader.

To prevent your trunk from “burning,” apply the fertilizer at least two inches away from the tree trunk.

Then, water the soil and allow it to penetrate to the roots.

Note: Apply the fertilizer in a circle equal to the tree’s height. By this, the fertilizer will reach the root system of the tree.

For example: Let’s say that your tree is 10 meters long. The perimeter (circumference) of the circle should then be 10 metres roughly.

For citrus and lemon trees, remember that they require more Nitrogen as they get bigger.

Can I use 18-18-18 Fertilizers For Potatoes?

Quick answer: It can be used at the time of planting. But we have better options as well.

Here’s a thing.

Growing potatoes can be a bit tricky. They need well-draining soil, full sun, and a temperature between 50-70 ℉.

Can I use 18-18-18 fertilizers for potatoes

But which fertilizer works best?

Before discussing this topic, you should know that potatoes have a high nutrient requirement. Here are some side nutrients essential for potato growth:

  • Boron: It improves potato skin texture. Plus, it allows calcium to be absorbed from the soil.
  • Magnesium causes better growth in low pH (acidic), and sandy soils.
  • Manganese: It decreases the pH of high-pH soils.

You should change fertilizers when growing a potato plant. Let me explain.

The potato plant requires around 3 to 4 months to develop. So here are the requirements at each stage:

  1. When planting: A triple 15 fertilizer (15-15-15) is ideal. You can use 18-18-18 fertilizer as well.
  1. 1-2 months after plantation: A fertilizer high in Nitrogen (such as 34-0-0) is required.
  1. For the last month before harvest: The plant requires more Pottasium. So 14-7-21 fertilizer can work best at this stage.

If I talk about the amount of fertilizer, 25 pounds is added to a 1,000-square-foot potato garden (generally). In short, you can apply the triple 18 fertilizer at the time of plantation.

Can I Use Triple 18 Fertilizer For Grapes?

If fertilizers are applied correctly, the growth of grapes can improve massively.

In short, it depends on your soil. But for grapes, you can go for other options as well. Let me explain.

Nitrogen is essential throughout the process.

It is essential for fruit development. If you use a proper fertilizer, the size of the grape will be bigger. Plus, the growth will be faster as well.

Regarding phosphorus, its primary function is to ensure robust, deep and healthy roots. This will help the grape plant to absorb more nutrients during its early stages. Potassium:

Potassium serves the purpose of protection for the plant. The potassium in the NPK fertilizer will lead to the healthy growth of the grapes. Plus, it will protect them from various diseases.

The NPK 18-18-18 fertilizer can be a good source of Nitrogen (N), Phosphorus (P) and Potassium (K). But, an ideal fertilizer is 10-10-10 for grapes.

Wrapping Up:

With this, our topic “what is 18-18-18 fertilizer used for” has ended.

In short, this NPK fertilizer is an excellent source of plant macronutrients. This fertilizer can also be good for the maintenance of your lawn and garden.

Remember that over-fertilizing your plant can cause chemical burns. So it would be best if you were extremely careful when using this fertilizer.

To recap, we discussed the uses of triple 18 fertilizer. Plus, we learned whether it could be used for potatoes, grapes, and lemon trees.

If you have any questions, feel free to get in touch. Stay tuned for more.

What is 18-18-18 Fertilizer Used For? | Best Guide

Leave a Reply

Your email address will not be published. Required fields are marked *

Scroll to top