What do the numbers on fertilizer mean and which one do you need? There is a lot to discuss and a lot of opinions and misconceptions about fertilizer. I want to share what I know and some of my experiences but ultimately you should decide what is best for you and your specific conditions.
The Numbers
There are several percentage amounts on a fertilizer label. Fertilizer companies are required by law to list their contents. State and federal laws mandate that manufacturers display the exact percentage of primary plant nutrients—Nitrogen (N), Phosphorus (P), and Potassium (K)—on the product label. They must also list the specific sources of these nutrients and provide warnings for any harmful ingredients. Organic fertilizers are typically lower in these percentages than synthetic fertilizers. Many fertilizers contain micronutrients like iron, zinc, magnesium etc.. as well. Plants (or trees, or grass) require a full spectrum of nutrients in varying amounts in order to be healthy and productive. If some of these are missing or are not available in the correct amounts your plants will suffer. What a particular plant needs varies depending on several factors like plant type, location, soil type, soil pH, sun exposure etc…
Fertilizers are often confused with compost. Fertilizers are concentrated nutrients that plants need to grow- Think “food for the plants”. Composts do contain small amounts of these nutrients but are used more to enhance soil health and texture.
Organic vs Synthetic
Synthetic fertilizers became popular after World War II, spanning the late 1940s and 1950s. During this time, governments and companies transformed wartime explosives factories into commercial plants that mass-produced nitrogen for farming. This era made fertilizer convenient and easy to apply and drastically increased global food production. These are also called chemical or inorganic fertilizers. Organic fertilizers are derived from natural sources like feather meal, bone meal, blood meal alfalfa meal etc…Organic fertilizers have the added benefit of adding organic matter to the soil. While there are many opinions about which type of fertilizer source is best the truth is that the plant doen’t know the difference. Plants can only absorb nutrients when they are dissolved in water and exist as ions. Once the nutrient is in the ionic form neither the plant nor the lab can tell a difference in where it came from. So, the choice is yours.
What Ratio Is Good For My Plants?
When you go to the fertilizer isle you see fertilizer for this plant or fertilizer for that plant or this ratio or that ratio. Different plant types require different ratios of nutrients. Plants share seventeen essential nutrients, but their specific needs vary. For example, grasses need more phosphorus than trees. Some vegetable plants needs change as they grow. Instead of looking for a specific fertilizer with a plant type listed (Plumeria Food) look for a good balanced fertilizer that can be used on a variety of similar plants.
Our nursery guides customers to 3 basic fertilizer types: Flowering plants, Trees/Shrubs/ and Lawns, and Vegetable gardens (organic fertilizer).
Flowering plants generally need a higher first and middle number- we have seen great results with a 19-13-6.
Trees/Shrubs and Lawns do well with a 3-1-2 or 4-1-2 ratio or something close on the numbers- ex. 18-4-9, 15-5-10, 21-7-14.
We have had success on our vegetable gardens with an organic 8-3-5 or 6-8-4.
More About Fertilizers
While we have several brands of both synthetic and organic each with their own idea of what is a good ratio, the question still comes back to “what are you using it on?”. Choose a fertilizer based on your needs and an experienced nursery professionals’ recommendation. There is not room in this article to go in depth on fertilizer ratios, nutrient sources, application rates and application timing. I will address this in the future, probably across multiple posts. There is that much that can be talked about! Please leave any specific questions in the comments and we will get you the information that you need.
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