The single biggest mistake GTA homeowners make is treating fall as a wind-down. Lawn care in October and November is actually among the most impactful work of the year — and most people skip it.
Here's the fall routine that works for Ontario's freeze-thaw-heavy winters.
1. Keep mowing until the grass stops growing
In the GTA, grass typically stops active growth when nighttime temperatures consistently hit 5°C — usually late October. Keep mowing until then. Drop your mowing height slightly for the last 2–3 cuts of the season (to about 2.5 inches). This reduces snow mould risk by letting light reach the crown of the plant.
2. Do your final fertilization in late October
This is the most important fertilizer application of the year. A "winterizer" fertilizer (high potassium, low nitrogen) helps grass store energy in the roots for spring. Apply when the grass has stopped growing but before the ground freezes — usually October 15 to November 1 in the GTA.
3. Fall overseeding window is actually better than spring
Counter-intuitively, late August through mid-September is the ideal time to overseed in Ontario. Soil is still warm from summer, weed competition drops, and the seedlings get 6–8 weeks to establish before frost. If you missed it, spring is your second chance.
4. Leaf removal matters more than you think
A thick mat of wet leaves smothers grass and creates the perfect conditions for snow mould. Remove or mulch leaves before they mat down. If your leaves are less than an inch thick, you can mulch them with your mower. Anything more than that needs to be raked or blown out.
5. Aerate in early fall if you haven't done it in spring
Fall is actually the preferred aeration window for cool-season grasses. The soil is warm, grass grows into the holes before freeze, and there's less weed pressure than spring. Aerate when daytime highs are still above 10°C — typically September to mid-October in the GTA.
6. Clean out your beds and garden borders
Cut back perennials, remove annuals, and pull any remaining weeds before freeze. Adding a fresh layer of mulch (2–3 inches) over your beds in October insulates roots and suppresses winter weeds that germinate in early spring.
7. Winterize irrigation if you have it
Any irrigation system in Ontario needs to be blown out before the first hard freeze. Leftover water in pipes and heads expands when frozen and cracks everything. Book this for late October — it's often done the same day as leaf cleanup.
Fall timeline for GTA homeowners
- Late August – Mid-September: Overseed thin patches (best window)
- September – Mid-October: Core aerate if needed
- October: Leaf cleanup (ongoing as leaves fall), final mowing, winterizer fertilizer
- Late October – Early November: Final leaf haul, mulch beds, winterize irrigation