What is Fertilizer?
(And how do I know what fertilizer my plants need?)
One of the most common questions we get here at Seascapes is “What fertilizer do I need for my ________?” Different plants require different nutrients, and at different levels. Fertilizer can help to provide these sought-after nutrients. Although there is a long list of nutrients your plants require, the three most common nutrients found in fertilizer are Nitrogen (N), Phosphorus (P), and Potash (K). You will often see “N-P-K”, or a three-number combination, noted on a bag of fertilizer, which stands for the ratio of these nutrients contained in that specific fertilizer. Before we can understand how much of these nutrients your plants need, let’s break down why these three nutrients are so important to your plant’s health.
Knowing how to read a bag of fertilizer will help you to better understand what you’re buying and what will work best for your garden. Look for the three numbers on the front of the bag, separated by dashes. Most fertilizers make the N-P-K big and bold near the center of the bag so you know what’s in it. The numbers represent a ratio of these nutrients contained in that specific fertilizer. Reading the full list of ingredients will tell you what other micronutrients are in the bag.
When searching for a balanced fertilizer, the three numbers will be equal ratios. The ratio could be a 10-10-10, but a 20-20-20 is also a balanced ratio, with higher percentages of those three macronutrients. A fertilizer that contains only one macro-nutrient will have “0” in the other values. For example, if a fertilizer is 10-0-0, then it only contains nitrogen. Fertilizers also contain a number of other nutrients in smaller quantities. The micronutrients include calcium, magnesium, sulfur, boron, copper, iron, manganese, zinc, chlorine, and cobalt.
In order to know what nutrients your soil is missing, it’s best to test your soil and find out the pH level. This can help to determine what your soil is lacking. If the soil acidity is too high or too low, the nutrients may be locked up and not available to plants. A simple soil pH test can tell you whether the soil is good for what you want to grow. Levels between 6.2 and 6.8 are ideal for vegetables but not suitable for flowering plants and fruits.
Although you should test the pH of your soil, you can still know what fertilizers to look for when shopping around for the perfect boost for your plants. Flowering plants require a relatively balanced NPK, typically a 1-2-1 ratio or equal. We carry a 4-8-4 fertilizer for flowering plants. Hibiscus specifically benefit from a 2-1-3 ratio, but anything with a low P and high K number will help promote blooming. In contrast, vegetables require more nitrogen, so a 5-2-4 ratio would be marketed to promote vegetable growth. If you’re looking to fertilize turf, an 8-0-4 is recommended, but be sure to read application instructions carefully to ensure your grass doesn’t burn. Something like palms can be a little trickier. Research has indicated that palms benefit from a 3-1-3 fertilizer but require more than just the three macronutrients. Palms require extra magnesium, calcium, and manganese, so be sure to look for a product that contains more of these micronutrients. If you have a variety of plants to care for and are looking for a general all-purpose fertilizer, a 6-4-4 is typically sold as such. But again, knowing the pH of your soil and targeting specific nutrients for different types of plants will help you better feed your plants!
Knowing what to look for when you’re shopping for the perfect fertilizer will help you make confident purchases and feel good about what you’re feeding your plants! No fertilizer is created equal, in fact they are all unique! And knowing what ratio will work best for your specific plants will ensure they’re getting the right amount of nutrients to grow strong!