How to Choose the Right Lawn and Plant Fertilizer

To create a beautiful green lawn that's the envy of your neighbourhood or a healthy and abundant garden, you need to use a good fertilizer. Learn all about the nutrients that your plants need and how to feed them properly to get the best results.

Essential Fertilizer Components

Your lawn and plants receive oxygen, carbon, and hydrogen from the surrounding environment, but they also require other nutrients that may not be as readily available. The soil needs to be regularly replenished, and this is where fertilizer comes in.

Fertilizers provide the essential nutrients of nitrogen, phosphorus, and potassium—which are reflected on the fertilizer label as NPK. Each one is necessary for a different part of plant development.

Nitrogen (N): Responsible for leaf growth, gives leaves their green colour.
Phosphorus (P): Responsible for root growth.
Potassium (K): Aids in root development and resistance to disease—sometimes called potash.

The label tells you what percentage of each nutrient is present in the fertilizer by weight. For example, a 16-4-8 fertilizer contains 16% nitrogen, 4% phosphorus, and 8% potassium. The remaining 72% is inert filler material, like clay or limestone, which helps prevent chemical burn and evenly distribute the fertilizer. There may also be some secondary nutrients or minor elements present in the formula.

Pro Tip

To find out the weight of each nutrient in the fertilizer, multiply its percentage by the total weight of the bag. For example, a 50 lb bag of 10-10-10 fertilizer has 5 lb of each nutrient.

All-Purpose Plant Foods

The fertilizer family also includes all-purpose or general plant foods intended for houseplants. These fertilizers usually come in smaller and more portable packages and are available in granular form, liquid form, spikes, and tablets.

Some plant foods are specifically formulated for indoor plants like cactus, African violets, and flowering plants. These formulas are usually higher in phosphorus to aid the growth of flowering plants and higher in nitrogen for foliage plants.

You can also find foods for outdoor plants like roses and rhododendron. Spikes and tablets are a particularly convenient option, especially when used in containers that allow the nutrients to leach out by watering.

Specialized Lawn Fertilizers

Lawns have their own unique fertilizer requirements, which depend on both the type of turf you grow and on the season. Before you purchase a lawn fertilizer, make sure you read the label carefully. There are a variety of lawn foods containing varying amounts of nitrogen, phosphorus, and potassium. Lawn fertilizers are also commonly combined with pesticides.

Pro Tip

If you have a dog, you'll have to take some simple precautions when applying lawn fertilizer. Though exposure isn't extremely dangerous, it can cause mild gastrointestinal issues. Manufacturers typically recommend that you keep your dog off the lawn for 72 hours after fertilizer application. Make sure you also water the fertilizer in before allowing your dog back on the grass.

Weed and Feed Fertilizer

“Weed and feed” is a term used to refer to fertilizers that also contain a weed killer for grassy weeds and broadleaf weeds like crabgrass and dandelions. The label will list the specific weeds the product is intended for. There are two main types of weed and feed fertilizers.

Pre-emergent: Commonly used for crabgrass, pre-emergent weed and feed fertilizers must be applied early in the season, before the weed seeds have a chance to germinate. They are not effective for actively growing weeds.
Post-emergent: Effective for weeds that are actively growing, post-emergent weed and feed fertilizers kill weeds on contact. They do not kill seeds that haven’t germinated yet.

Applying pre- and post-emergents at the proper time is key to ensuring success, as they won’t do their job if applied too early or too late. If you are also sowing grass seed, then make sure you leave an adequate time interval between sowing and fertilizing. Reading the label carefully will help you pick the right product for your needs.

Pro Tip

Starter fertilizers and winterizers help boost lawn root growth by providing extra phosphorus. Starter fertilizers should be applied to newly seeded lawns, while winterizers are used for the last fall feeding.

Organic Fertilizer

You also have the option to feed your lawn and garden with non-synthetic, organic fertilizers, soil additives, and soil conditioners. Organic fertilizers are usually applied more frequently because they lack ingredients for slowing down nutrient release. Just like synthetic products, they need to be applied with caution and care.

Some common organic fertilizer alternatives include:

Compost: A fantastic, all-around material for improving garden soil.
Manure: Used for soil conditioning. “Hot manure” from pigs, poultry, and horses is high in nitrogen and must be composted first to prevent nutrient burn. “Cold manure” from cows, rabbits, and pigs can be applied to the soil directly.
Greensand: Sourced from marine sedimentary deposits. Provides potassium and iron.
Blood meal: A phosphorus-rich byproduct of the meat-packing industry that has been steamed and dried.
Fish emulsion: A mild and non-toxic byproduct of fish processing often used for tender plants to prevent fertilizer burn. Has a strong odour.
Cottonseed meal: A cotton-processing byproduct that is rich in nitrogen.
Superphosphate: A combination of rock phosphate and sulfuric acid that plants find easy to absorb.

Tips for Applying Fertilizer and Getting the Most Out of It

Maximize your time and efforts by following these five tips for fertilizer application.

1. Perform a Soil Test
Soil nutrients need to be routinely replenished as they deplete over time. Even if your soil looks dark, it might not contain all of the necessary nutrients. A soil test will tell you which nutrients are already present in the soil and which are missing. It will also tell you the soil pH. Lime is used to raise the pH and make soil more alkaline, while sulphur is used to lower the pH and make soil more acidic.

2. Apply the Fertilizer Correctly
Fertilizer needs to be applied at the correct time and in the proper amount. A slow-release fertilizer, for example, should not be applied late in the growing season as you don't want to encourage foliage growth just before winter. Applying more fertilizer than the plant can absorb at once also harms the plant and wastes the fertilizer.

3. Practice Crop Rotation and Intercropping
Every plant requires its own specific nutrients. Rotating the plants in your garden allows for efficient uptake of the available nutrients in the soil. Planting different varieties of plants together—a practice known as intercropping—also allows you to get the most out of your soil. Companion planting lets the natural qualities of each plant complement one another.

4. Use Green Manure
“Green manure” refers to cover crops that are planted with the intention of getting worked back into the garden soil. Cover crops are picked for their nutrient values and used by commercial agriculture growers and serious home gardeners alike.

5. Keep Safety in Mind
Excess fertilizer runs the risk of seeping into the ground and affecting the water table or running off into nearby areas and ending up in the water supply. Always read the package directions for proper application procedures, safety precautions, and application attire.