Home & Garden Gardening

What Is Plant Fertilizer?

    The Basics

    • Fertilizer is a liquid or solid mixture put directly on plants or into their soil to help give them get the food they need to grow and bloom to their potential. Different types are available commercially. To find out what kind you need, consider what type of soil your plant prefers and what the known pH preference is, which dictates how to change the soil nutrients. Ask your local master gardener or extension agent, or consult a nursery before making a purchase.

    Major Nutrients

    • Commercial fertilizers have a series of up to three numbers listed on the packaging. This tells you what percentage of the fertilizer has nitrogen, phosphorus and potassium, dubbed macronutrients. The term "complete fertilizer" does not mean it has everything, it just means that all three are present. Do not use a brand without all three unless you plan to supplement it in another way. The rest of the product contains filler and less important nutrients.

    Other Nutrients

    • There are 16 known nutrients that help plants stay healthy. Some of them are required in very small doses, and too much of them is harmful. Calcium, magnesium and sulfur are called the secondary group, affecting the alkaline or acidity of soil. Called micronutrients, iron, boron, chlorine, zinc, manganese and molybdenum are helpful to plant roots but are sometimes lacking in soil. These can be added or soil pH changed to give the plant a boost.


    • When organic compost is available, use it. Rich in microorganisms and environmentally friendly, no synthetic or commercial product can do what Mother Nature does naturally. Decomposing materials such as rotting leaves, grass clippings and pine straw from the yard offer rich food for plants. Egg shells and vegetable scraps are recyclable donations from the kitchen and garden and are staples in a compost pile. Be sure the compost is close to resembling soil in appearance before using.


    • There are five main types of commercial fertilizers. Apply foliar liquid directly to leaves to give plants a quick boost in warm or cool weather. Granular, a favorite for bushes like azaleas and roses, must be mixed with soil about a month before planting. Dilute liquid fertilizers with water through spray nozzles. Slow-release fertilizers expel nutrients according to soil moisture over time. Organic fertilizers are made from compost, manure, seaweed and other natural components.

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