It’s that time of year again! We are freshening up our garden beds or perhaps starting new ones. Asking questions at your local garden center about the steps you should take to ensure the health and development of your garden may lead to a conversation about fertilizer and its NPK ratio. Any expert will be able to tell you what this means, but knowing what NPK is ahead of time will help your conversation flow much easier.

What is NPK anyway?

N stands for Nitrogen, P is Phosphorus, and K is Potassium. Each element has its own job and together, the term NPK refers to the ratio of these elements in a fertilizer or soil amendment. Nitrogen (N) is responsible for strong stem and foliage growth. Phosphorus (P) aids in healthy root growth and flower and seed production. Potassium (K) improves overall health and disease resistance of the plants.

What do the numbers mean?

Please don’t make the mistake of thinking that the greater the numbers of NPK in your fertilizer the better off your plants will be. Too much nitrogen will make for quick growth but develop weaker plants that are prone to disease and pests. Excessive levels of Phosphorus are hard to achieve because it often washes out of the soil with rainfall. Potassium is necessary for the metabolization of sugars and water uptake. You will notice that if you add up the numbers they do not equal 100%. Most fertilizers, whether organic or chemical, contain other nutrients or fillers. The best way to determine what NPK ratio in fertilizer is best for your soil is to get a soil test at your local garden center or purchase a soil tester and test it yourself. This will allow you to choose the best fertilizer for the soil you are planting in.

 How do you choose?

If you simply don’t have the time to have your soil tested but still want to provide the necessary nutrients for healthy plant growth, an all-purpose 5-5-5 fertilizer will do the trick.  You should be aware that the NPK ratio of synthetic fertilizer is typically higher than the ratio of an organic fertilizer. By law, the ratio can only detail the nutrients that are available. Organic fertilizers contain slow-release nutrients that become available over time and also contain many trace elements that synthetic fertilizers do not supply.

Applying fertilizer to your garden beds is a necessary step to ensure your garden’s success. Whether you are planting a new garden or simply reusing an old garden bed, the soil alone will not have enough nutrients to prevent disease and insect problems and allow for optimum growth. Plants require six primary nutrients: carbon, hydrogen, oxygen, nitrogen, phosphorus and potassium. Air and water provide the first three and the other three are supplied through the application of a good fertilizer.