When to Fertilize Your Lawn in Ontario: The Calendar That Works

The three windows

• Late May – early June: after the spring flush settles. Supports steady growth heading into summer without forcing soft, disease-prone top-growth.
• Early September: the most important feeding of the year. The lawn is recovering from summer, rebuilding roots and thickening up — this is when fertilizer moves the needle most.
• Mid-to-late October (winterizer): a final feeding the lawn stores in its roots. This is why fall-fed lawns green up weeks earlier in spring.

Why fall beats spring

Heavy spring feeding produces fast blade growth that looks great for two weeks, then leaves the lawn thirsty and tender going into summer. Fall feeding goes into roots and reserves instead of leaf — thicker turf, earlier green-up, better drought tolerance. If your budget covers one application a year, make it September.

What we apply and why

We use slow-release granular fertilizer matched to the season — steady feeding over six to eight weeks instead of a surge-and-crash. Ontario’s cosmetic pesticide rules mean weed-and-feed products with traditional herbicides aren’t on the menu here; the honest path to a weed-free lawn is a thick lawn, which is exactly what a proper feeding calendar builds.