Located in Zone 3a where winter temperatures can drop to minus 40 on both scales, Edmonton is also ablaze with flowers in the summers. Gardeners use every opportunity to tend their plants, including early fertilization in the spring to enrich the soil so it is ready to nourish plants when they emerge.
The City of Edmonton's Good Growing brochure recommends several steps in spring to apply fertilizer effectively for optimum plant growth.
Prepare the soil to fertilize your Edmonton garden by breaking up compacted areas by aerating them. For small spaces this can be as easy as walking around with spiked shoes (such as golf or running shoes). For larger areas you can use a roller with spikes. The holes allow oxygen, water and the nutrients from fertilizer to reach plant roots.
Remove all thatch left over from the previous season. The debris that builds up in Edmonton lawns and gardens, including grass clippings, fallen leaves and dead growth, will keep fertilizer from penetrating to the plant roots. Scrape off the thatch cover with a fan rake. If your thatch is thick, use a mechanical dethatcher or power rake to remove it every few years.
Once the lawn and flowerbeds are aerated and debris removed, Edmonton's Good Growing group recommends applying a layer of compost to supply your plants with a mix of nutrients plus organic material and mircoorganisms that enrich the soil. Compost, which won't leach into groundwater, is easy to make in your own backyard from kitchen and garden wastes.
While you're working in the garden, overseed the lawn with grass seed and then cover with a layer of compost for a thick lawn that will crowd out weeds naturally. Denise Hodgins in the Edmonton Sun suggests applying 2 lbs. (about 900 g) of grass seed for every 1,000 sq. ft. (93 sq. meters) of lawn.
Organic fertilizer encourages the growth of beneficial bacteria, breaks up the soil with organic material and promotes steady growth. Ideal for Edmonton's intense climate, organic fertilizer doesn't burn lawns or plants and isn't toxic or corrosive. Commercial organic mixes are made from animal sources, sewage sludge, dried blood and other natural sources. Most of them are slow-release, so the nutrients are available over the growing period, providing constant food for the plants.
When Edmonton's temperature warms to 20 degrees Celsius, usually in mid-May, apply slow-release chemicals if you prefer synthetic fertilizers. These break down slowly in the soil to provide a constant supply of nutrients to your plants. Waiting until the soil is warm allows the chemical fertilizer to soak into it and prevents the chemicals from running off frozen ground and getting into the water table.
The Edmonton BBB recommends a fertilizer with a ratio of four parts nitrogen to one part phosphorous and two parts potassium (4-1-2) to help spring plants begin the growing season.