Fertilizer 101: everything you need to know

A trip down the garden centre's fertilizer aisle can be overwhelming. With so many choices to weed through, how do you know which product to pick? This guide gives you the knowledge to walk down that aisle with confidence.

Fertilizer 101: everything you need to know

First things first

Before you set foot in the fertilizer aisle, test your soil.

  • Contact your local garden centre for information or look online for a certified soil-testing lab.
  • The test results give you an idea of what nutrients your soil may be lacking so you can purchase a fertilizer that will add those nutrients.
  • On most fertilizer products, you may notice a set of three numbers.

What those numbers mean

These numbers indicate five per cent nitrogen, 10 per cent phosphorus and five per cent potassium.

  • Nitrogen (N) encourages green, leafy growth.
  • Phosphorus (P) contributes to root development.
  • Potassium (K) helps maintain vigorous growth.

Complete and incomplete

A complete fertilizer contains all three elements (nitrogen, phosphorus and potassium), while an incomplete fertilizer contains just one or two.

  • If a fertilizer is lacking a nutrient, there will be a zero in its place on the label (15-0-0).
  • A soil test is the best way to determine whether you need to compensate with a complete or incomplete fertilizer.

General- and special-purpose

  • General-purpose fertilizers contain all three nutrients and are intended to meet basic needs of most plants and grasses.
  • Special-purpose fertilizers are formulated to meet specific gardening needs.
  • Compare labels to find which fertilizers best fit your lawn needs.

Liquid and solid

Fertilizers are applied in either dry or liquid form. Dry fertilizers are worked into the soil and begin releasing nutrients when they come in contact with water. The nutrients are either delivered to the soil quickly or, if you use a slow-release variety, over a period of several months.

  • Slow-release fertilizers are appealing because they need less-frequent applications and provide a slow, steady diet throughout the growing season with minimal effort.
  • While you can find ready-to-use liquid fertilizers, they are typically sold as concentrated liquids or granular substances that need to be diluted with water before you use them.
  • Liquid fertilizers are applied to the soil at very diluted solutions. Most deliver nutrients to a plant or grass quickly and need to be applied a few times during the growing season.
  • Liquid fertilizers are ideal for container plants or as a supplement to dry fertilizers when you want to give annuals, vegetables or your lawn an extra boost at the beginning of the season or during periods of active growth.

Organic and synthetic

Organic fertilizers, such as bone meal, fish emulsion and chicken or worm manure, are made of materials from once-living organisms.

  • Unlike synthetics, which immediately release nutrients through water, organics share their bounty as they break down.
  • Although synthetic fertilizers work well for plants or grass that need an instant boost, organics are less likely to damage a plant or your lawn if accidentally over-applied.
  • Besides their environmentally-friendly nature, organics are also known for their ability to deliver nutrients while enhancing soil health.

Sticks, stakes and pellets

These fertilizers bear a resemblance to giant-sized vitamins, and that description actually isn't too far off.

  • The fertilizer has simply been compressed so it can be inserted into the soil around the plant, tree or shrub.
  • The idea is to get the nutrients to the plant's roots as quickly as possible by burying the fertilizer nearby.
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