Plants need nutrients, but adding fertilizer without knowing what the soil needs can waste money, harm plants, and send extra nutrients into waterways. Start with a soil test when you can. It can tell an adult which nutrients—and how much—your garden needs.
- A fertilizer label usually shows three numbers called the N-P-K analysis.
- The first number is nitrogen (N), the second is phosphate (P), and the third is potash (K). They show the percentage by weight of each nutrient in the product.
- Different plants and soils need different amounts. A bigger number is not automatically better.
- Read the entire label. It tells you which plants the product is for, how much to use, how to apply it, and what safety precautions to take.
- Ask an adult to handle fertilizer. Keep children and pets away while it is being measured and applied.
Nitrogen
Nitrogen is important for green leafy growth. Too little can cause pale or yellow older leaves, but too much may burn roots, produce weak growth, delay flowers or fruit, and pollute water. Slow-release products supply nitrogen over a longer time, but they still must be used at the labelled rate.
Phosphorus
Phosphorus supports roots, energy transfer, seeds, and fruit. It moves slowly through most soils and can build up when too much fertilizer or manure is repeatedly added. Use a soil-test recommendation rather than adding extra phosphorus “just in case.”
Potassium
Potassium helps plants regulate water and supports sturdy growth. A soil test can show whether your garden needs more. Symptoms that look like a nutrient shortage can also be caused by root damage, weather, insects, disease, or incorrect watering, so do not diagnose a plant from leaf colour alone.
Fertilizing Seedlings
Seeds contain enough stored energy to germinate. Seedlings grown in a soilless mix do not need fertilizer until they have several sets of true leaves.
- Choose a general-purpose, water-soluble fertilizer whose label includes seedlings.
- Ask an adult to mix it at one-quarter of the label strength, unless the product gives its own seedling rate.
- Use it no more than once a week; use plain water as needed the rest of the week.
- Mix only what you need. Keep the original product in its original labelled container, tightly closed and out of reach of children and pets.
- Never store fertilizer or diluted fertilizer in a drink bottle or an unlabelled container.
Wash your hands after gardening and after handling any garden product. If fertilizer gets in someone’s eyes, on their skin, or in their mouth, tell an adult immediately and follow the first-aid directions on the label.