How to Read and Understand Fertilizer Labels

Browsing through a garden center or here with us online creates a sense of beauty. But it can also be very confusing 🥺 when looking for fertilizers for your plant as a beginner plant parent.

You find the shelves filled with fertilizers, and you must make the right choice to keep your plants healthy. All those bottles and packets can make your head spin.

What are all those bags and bottle, and what does the fertilizer labels with numbers mean? Does it matter what one you choose?

We are here to help you understand those fertilizer labels to choose the right one for your garden. Well, the truth is to have lush plants, you need to improve the soil; feeding plants is one way of doing this.

What are Plant Fertilizers?

plant fertilizer

To understand a fertilizer label, you must first understand what a plant fertilizer is. Fertilizers are natural ingredients or chemicals you add to the soil to make it fertile and help plants’ roots grow.

Maybe your mom drenched her plants with a blue liquid every week, and you may think you can do the same for your plant babies. Still, from the past to now, we have seen a considerable shift in fertilizing plants.

These days we think more about feeding the soil than our plants. But why do we think this way?

When you use organic fertilizers, you feed the soil. In turn, it feeds your plant growth. So, preferably skip that chemical blue stuff and move towards natural feeding to create organic gardening.

Using a naturally derived feed like organic matter instead of chemical nitrogen, phosphorus, and potassium helps plants with a more balanced nutrient source.

Hence, the organic matter will provide nutrition for your plants as it feeds the soil’s living organisms.

So, microscopic critters like fungi and bacteria will process the feed and break it down into micronutrients for plants to grow, and our plants reap the benefit.

Start With Organic Fertilizers Like Compost

Using organic fertilizers like compost is the best feed for developing healthy roots. It contains other nutrients you do not find in store-bought feeds essential for your plant’s growth.


It is a great food source for the microbes. It will encourage healthy soil every year when you do organic gardening. Still, sometimes you must provide your plant with additional nitrogen and phosphorus potassium.

Added nutrition will be needed when the nutrients in compost become depleted or unavailable. In these situations, you can find many natural fertilizers that do an excellent job on the market.

You can add them to your plants throughout the growing season, but you need to understand the fertilizer label on the bag or bottle 🍾 to get the most bang for your buck.

At the same time, you can keep excessive nutrients from polluting a waterway or harming your plant growth.

The first thing you will see when you read fertilizer numbers on a package are three numbers representing the N-P-K ratio.

What do The Numbers Represent on a Liquid Fertilizer Label

liquid fertilizer

You will spend much time reading the labels when you shop for fertilizers. Thus, it is essential to understand what the product label means and what ingredients they use to make the feed.

There are three numbers on every fertilizer label, whether it is a balanced fertilizer or a slow-release fertilizer ( NPK )

  • N-Nitrogen

  • P-Phosphorus

  • K-Potassium

These numbers represent three macronutrients in a package and are the fertilizer analysis by weight present in percentage.

While most plant growth depends on different nutrients, these three numbers are the most extensive amounts to fuel a plant’s development.

For example, you can have a bag of feed available with a fertilizer grade of 10-5-10. It is not a balanced one and holds the following:

  • 10% N-Nitrogen

  • 5% P-Phosphorus

  • 10% P-Potassium

Thus the remaining weight of 75% is a carrier product. So, next time you shop for fertilizer, read the label to get a list of ingredients with the fertilizer ratio.

The Difference Between Organic and Synthetic Fertilizer Numbers

When you compare organic with synthetic fertilizer grade, the N-P-K ratio is often smaller in an organic product. Thus you will see three numbers like 2-3-2 or 1-1-6.

The reason is that the label 🔖 percentages they base on the levels of the nutrients immediately available. This is why many nutrients contained in organic fertilizers are not immediately available when applied.

Hence, it works like a slow release of essential nutrients as the soil microbes take time to process these nutrients to release them for the plant.

Now, this may sound negative, but it is not, as the nutrients release slowly with time over a few weeks.

Interestingly, the study was done at the University of Massachusetts, where they noted that synthetic fertilizers released nitrogen within 3 to 6 weeks. Of this, only 40% to 60% is useable by plants.

Compared to an organic one like a fish-based liquid fertilizer, it releases nitrogen over 15 weeks, a whopping 90% used by plants.

Still, while an organic product is more expensive, you will get more nutrients over a long time, making it worthwhile to buy.

The Importance of N-P-K in a Balanced Fertilizer

plant fertilizer

As important as understanding the fertilizer grade, you must know how your plants use these three nutrients.

First Fertilizer Number Nitrogen

Nitrogen is a component of the molecule chlorophyll to help promote root and leaf development. Adding high nitrogen fertilizers like 6-2-1 or 10-5-5 to a fruit or flowering plant provides excessive green growth. Sometimes it will expense flower or fruit production.

So, giving it to a lettuce or spinach will make more sense. The reason is that your green leafy vegetables will need higher amounts of nitrogen.

The Second Fertilizer Number Phosphorus

Cell division in plant metamorphosis needs phosphorus to generate new tissues. It will help promote root growth and can encourage flowering or fruit production. Thus root crops depend on phosphorus, like beets, carrots, and onions.

So, investing in a fertilizer high in phosphorus, like rock phosphate or bonemeal, comes highly recommended. The rule is to choose a high-content phosphorus fertilizer product for plants producing flowers and fruits.

The Third Number Potassium

Potassium triggers certain enzymes and will help regulate the carbon dioxide update in plants as it controls the pores on the leaf surface known as the stomata. Hence, the potassium levels influence your plant’s vigor.

What’s in a Package of Slow-Release Fertilizer?

While most fertilizers, like synthetic ones, are made from salts manufactured in a factory, other filler ingredients comprise the bag’s weight. Sometimes you will not find the ingredients listed on the label.

In a natural feed, you find blends of naturally occurring materials, and the main ingredients are:

  • The plant material is derived from alfalfa, corn gluten, cottonseed, or kelp meals.

  • Then you can have manure material present like pelletized poultry manure, bat guano, dehydrated cow 🐮 manure, or worm castings labeled.

  • Then you have added animal by-products of the food industry, like bonemeal, fish emulsion, crab meal, blood meal, and more.

  • Some products can contain mined minerals like rock phosphate, greensand, sulfate of potash, or crushed limestone.

When you use a fertilizer with the combination above, you can feed the soil when the nutrients become depleted, and you cannot add more compost.

What Trace Elements Should You Choose?

When choosing the right fertilizer numbers with nitrogen, phosphorus, and potassium, it helps first to do a soil test. The soil test results will determine what you need. But making the best choice when it comes to choosing natural fertilizers, you have two choices as follows:

Complete Granular Fertilizer Blends

You can find dozens of brands for complete granular fertilizer blends. The majority combine the above materials mentioned above. Still, depending on the brand, the fertilizer numbers can be 4-5-4 or 3-3-3 or similar.

But what makes them different is that they contain all three essential nutrients with added traces of nutrients, vitamins, and other healthy goodies. Hence, it will work for a longer period to give your vegetation the nutrients needed to grow.

You can find blends tailored for crops or flowers growing in your garden. Hence, it has more of the primary micronutrients available.

Liquid Fertilizers

Using a feed in liquid form, the plant absorbers the micronutrients through the foliage and roots. The fertilizer provides a more readily available nutrient instead of being used longer. Still, instead of turning to salt-based products, look for organic ones.

liquid fertilizer

These are usually made of fish emulsion, liquid kelp, compost tea, or liquid bonemeal. Furthermore, using these products will reduce the risk of root burn.

Know Your Fertilizer Before You Throw

Before tossing a handful 🤏 of fertilizer on your vegetation, ensure they need it. Do a simple soil test to see what nutrients it needs. You can then avoid using an incomplete fertilizer.

The soil might need secondary nutrients instead of primary macronutrients like calcium or magnesium instead of nitrogen, phosphorus, and potassium.

Once you determine the fertilizer numbers and nutrient content needed, you can calculate it with the bag weight and label available. You can do a soil test every few years, and it will tell you other important information about the soil’s health, like the pH level.

But even if you start with a test of the soil, always recommend the bare minimum and follow the application rates you find listed on the label. So, invest in organic fertilizers for the best growing season ever.

Frequently Asked Questions

For example, when applying fertilizer to a lawn, it is recommended to use 2 to 3 pounds for every 100 square feet of your garden area. Thus two cups of fertilizer weigh one pound.

A fertilizer product’s calcium, magnesium, and sulfur are the secondary macronutrients, as vegetation needs them in smaller amounts than nitrogen, phosphorus, and potassium to improve soil health.

It is a balanced fertilizer you can use at all stages of plant development in a vegetable garden. Hence, it contains equal parts of the primary micronutrients of 20% nitrogen, 20% phosphorous, and 20% potassium.

When using a granular fertilizer, it usually is one teaspoon per gallon of water.

It is best to dilute the feed in a fertilizer ratio of 1/4 to 1/2 a teaspoon per gallon of water for potted plants.

Never mix a dry fertilizer with flowable dolomite, as it causes an excessive ammonia release. While mixing a phosphorus one with calcium nitrate causes it to salt out.

Whether you want to buy, sell, or simply reach out to other plant enthusiasts, Plantly is the right place to be!

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