Fertilizer Basics

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If you are ready to take your gardening to the next level, it is time to get serious about fertilizer. There are a lot of options but once you understand the basics, it really is very simple to get started. Here is what you need to know:

What is a Fertilizer?

Fertilizer is a substance added to the soil to improve its fertility. Many elements contribute to a soil’s fertility. There are three major elements (macronutrients) that all plants need: Nitrogen (N), Phosphorus (P), and Potassium (K). These elements are needed in large quantities and are not readily available in most soil. There are also seven minor elements (micronutrients), which can be found in varying degrees in fertilizer: Zinc, Manganese, Boron, Iron, Copper, Molybdenum, and Chlorine. The right fertilizer analysis in the soil is important for several reasons. First, a healthy plant resists insect and fungus damage much better than an unhealthy one. Second, proper nutrition promotes more consistent plant growth and bloom development. Third, it encourages better root development.

How Much Fertilizer Do I Need?

The amount of fertilizer needed depends on the current analysis of your soil. Garden centers and nurseries sell inexpensive soil test kits that will give you a good idea of the nutrients in your soil. Once you understand what nutrients are lacking, you can choose the most appropriate fertilizer.

Avoid applying fertilizer to a plant that is already stressed by drought, disease or pest damage. Do not apply fertilizer at the same time you plant, transplant, or prune. Allow the plant to recover for a few weeks first, make sure it is well hydrated, and then fertilize.

What do the Numbers on Fertilizer Mean?

There are three numbers listed on each bag of fertilizer. These are literal percentages of the macronutrients N-P-K that are in that bag of fertilizer. For instance, if the numbers read 31-3-10, then 31% of the bag is Nitrogen, 3% is Phosphorus, and 10% is Phosphorous. The numbers are always printed in the same order: N-P-K. Very often, the numbers do not add up to 100%. If this is the case, other minor elements and fillers are also included in the bag.

What Does Each Major Element Do?


  1. Promotes vigorous blade, leaf and stem growth
  2. Encourages dark green color
  3. Assists in chlorophyll production
  4. Improves overall plant health, quality, and density
  5. Aids in tolerance to heat, cold, and drought stress


  1. Promotes early plant development
  2. Hastens plant maturity
  3. Promotes bloom, fruit, and root development


  1. Improves tolerance to drought, disease and heat
  2. Increases winter hardiness
  3. Aids in water uptake
  4. Enhances overall health and vigor

Why Use a Special Purpose Fertilizer?

Special-purpose fertilizers are formulated for specific plant and soil needs and are generally grouped as follows:
Fertilizers to Stimulate Growth: Specifically designed for a season of active growth, and often used in the spring, when you want to encourage optimal growth, these fertilizers usually have a large nitrogen concentration, with N-P-K ratios such as 16-6-4.

Fertilizers to Stimulate Production: Other special fertilizers are designed to stimulate flower or fruit production. To help achieve these goals, such fertilizers usually contain low doses of nitrogen; for example, this type of fertilizer might have an N-P-K ratio of 3-20-20. For best results, apply the fertilizer once plants have been established and there is visible growth; you can apply it dry or in a liquid form.

Plant-Specific Fertilizers: These fertilizers boost N-P-K ratios designed to properly nourish and achieve premium results from a specific plant and have proven especially useful for citrus trees and acid-loving plants like camellias and rhododendrons. When you are shopping for fertilizer, you will see many different options for plant groups like “tomato food” or “flower fertilizer,” and when used properly these can also be very effective.

Why Choose an Organic Fertilizer?

One advantage of organic fertilizers is they help to retain soil moisture by maintaining soil health. All-natural organic fertilizers release nutrients slowly, providing nutrients as they decompose. Due to this slow release action, it is almost impossible to kill your grass or plants by applying too much. Organic fertilizers also often contain additional nutrients, which can benefit plant health. The slow release of organic nutrients provides a ripe environment for beneficial microorganisms and earthworms.

Why Choose a Synthetic Fertilizer?

Synthetic fertilizers are made in a lab and as a result are fast acting and deliver nutrients more quickly than organic varieties, making them a good choice for plants that are really struggling. However, be careful with the application. With synthetic fertilizers, it is easy to kill your grass or plants by applying too much so use them as sparingly as possible to achieve the desired results. You can buy synthetic fertilizers in dry or liquid form, the dry granules are the most affordable option.

To get the most of your plants and your fertilizer investment, consult with your local nursery or garden center, where you can get custom advice for your best garden yet!