What Are Those Numbers on My Fertilizer For?

Many times I have heard people say that those numbers on thier fertilizer aren't that important as long as you get the first number as high as you can get. 

Well, those numbers DO have a meaning!  The numbers have meanings for specific times in a plants life and for ways to help your plants produce more fruit and flowers.  You just have to know a little about those numbers and what they mean.

I thought I would give you a quick lesson in reading the 3 numbers on your fertilizer.  This will help you understand more about what you are doing when applying fertilizer and your plants will love you even more!  The added bonus is that your neighbors will be jealous at how well your garden is doing compared to theirs!!

Let's use a basic fertilizer such as 6-7-7.  The first number, 6, lets you know that you have 6% Nitrogen (N).  The second number, 7, tells you that there is 7% of Phosphorus (P).  While the last number, 7, states that you have 7% Potassium (K).  The numbers stand for Nitrogen-Phosphorus-Potassium or N-P-K. 

Each nutrient is specific for different purposes in a plants growth.  Nitrogen is what a plant needs to grow in general and helps to give your plants that awesome "green" color. All plants need Nitrogen to help them produce more leaves and strong stems.  Most plants do not need much Nitrogen while others need as much (or more) as they can get!  Some high Nitrogen plants are corn, most grasses, many annuals and lantanas. 

Phosphorus is the nutrient that needs to be the highest for your flowering plants.  This is the "Flower Number"--meaning that Phosphorus is the nutrient that plants need to help them flower more.  With a larger Phosphorus number compared to Nitrogen and Potassium, plants will have more energy to flower than to produce leaves.  High Phosphorus numbers are what you need to use on your flower gardens and flower pots.  Make sure that fertilizer you buy that says "Flower Booster" has a larger Phosphorus number.  You want your Phosphorus as close as two times higher than your Nitrogen and Potassium as you can get!  Do check this!  I found a fertilizer labeled as a "Flower Booster" that had a LOWER Phosphorus number! 

The last number on fertilizer is for Potassium.  This is what I call the "Root Booster" number.  Potassium helps to boost root development in young plants.  For older plants, potassium is an "Immune Booster".  It helps the plant to fight off diseases and pests that invade a plants "space"!  A high Potassium number is good for new plants and for mature plants mid and late in the growing season.  This type of fertilizer is good even to use once a month or more during the growing season as an immune booster for your plants.  Look for a formulation of fertilizer with a higher Potassium while the Phosphorus is the lowest number. 

I hope this will help you to understand the numbers that are on fertilizer labels.  They have a purpose and the more you know about these numbers, the better gardener you will be!  I talk more about the different forms that fertilizer comes in and the different ways that plants take them in in the post Getting Started Gardening.

Let's get playing in the dirt!