A Beginner’s Guide to Fertilizer Product Labels

By Matt LeBannister
Published: July 24, 2018 | Last updated: May 4, 2021 08:06:41
Key Takeaways

Think you know what all those numbers on a product's label are all about? Read on to discover what might have been deliberately left out of the equation.

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For any beginner gardener, walking into their local hydroponics shop for the first time can be an intimidating experience. As a former hydroponic store manager, I witnessed the looks of disbelief given by first-time patrons when confronted with a multitude of products stacked on never-ending shelves, each labeled with a set of various ingredients and numbers. They appeared overwhelmed by the massive amount of great products now available to every grower.


With a bit of advice and some trust in the knowledgeable hands of your local hydroponic retailer, you can easily navigate the world of hydroponic products by understanding the wealth of information listed on each product’s label. But always remember to keep in mind that each state, province and country has different rules as to what information must be listed on a product label and each has different rules regarding what is prohibited from being listed.

What Does NPK Stand For?

The most visible numbers on plant fertilizer labels refer to the NPK levels that list the relative content or percentage of soluble nitrogen (N), phosphorous (P) and potassium (K) in the product. Nitrogen, phosphorous and potassium are the three most essential nutrients plants require large amounts of for growth, hence their priority placement on all fertilizer labels.


There is often confusion when we see two products with the exact same NPK ratios, yet they are priced differently. To save some money, one might be tempted to buy the less expensive product since, according to the labels, they are the same. Or are they?

What people might not know is that the more expensive product, such as a bloom fortifier, could contain over 20 more ingredients that are not listed on the label, such as amino acids, citric acid and ascorbic acid.

These ingredients could greatly improve your yield, yet in many areas companies are not allowed to list them on the labels or make any claims about performance. If you want a detailed list of ingredients contained in any plant fertilizer, visit the manufacturer’s website or give them a call. You can always consult your local hydroponic retailers who often have more info than the labels can offer.


Trace Elements

Compared to NPK, trace elements are needed by plants in smaller amounts. Trace elements include zinc, copper, manganese and iron to name the most important. There is also calcium, magnesium and sulfur, which are required in slightly larger amounts. They are all essential to plant growth and development yet they are not always listed on product labels.

If any of these elements are listed on a fertilizer label, they will be listed as a percentage of the overall content. The percentage will seem minute compared to the NPK listing but that is because your plants only need trace amounts of these nutrients. The difference between a quality fertilizer and a mediocre fertilizer is oftentimes just the content of trace elements each one contains.



Trying to find organic nutrient additives and fertilizers can be tricky. Many products are labeled as organic making it simple for the average consumer. Products that are listed as organic must be certified organic by an independent group, such as the Organic Material Review Institute (OMRI).

This levels the playing field and protects consumers by ensuring that there is a standard by which these products are judged. The tricky part comes when you realize that there are nutrient additives and fertilizers that could very well be organic, they just have not been submitted for certification.

Having a product certified organic can be a long, costly process and many small manufacturers simply cannot afford to do this. Their product may be as good and naturally organic as the certified competitor, but you would never know this by looking at the label. This is where having a conversation with the knowledgeable staff at your local hydroponic shop pays off. They have insight into products that goes beyond the label and can fill you in on what products will be right for you.

In Conclusion

There are so many great nutrient solutions and fertilizers on the market today making choices seem endless. The hydroponic industry shows no sign of slowing down and could very well be the future of agriculture.

Unfortunately, the product labels have not kept up with the growth of the hydroponic business. Just remember there is as much unsaid on product labels as is said. Have trust in the bevy of knowledge your local hydroponic retailer has gained over the years. They can help you navigate the rough seas that are fertilizer product labels.


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Written by Matt LeBannister

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Matt LeBannister developed a green thumb as a child, having been born into a family of experienced gardeners. During his career, he has managed a hydroponic retail store and represented leading companies at the Indoor Gardening Expos. Matt has been writing articles for Maximum Yield since 2007. His articles are published around the world.

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