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How to Fix a Patchy Lawn
Bare patches, thin spots, and the worn path the dog takes — fixed by overseeding done properly: seed pressed into real soil contact, kept moist for three weeks, at the time of year Ontario weather does half the work for you.
Overseeding steps · seed-to-soil contact · watering schedule · Easy — one afternoon · An afternoon + 3 weeks of watering
BEFORE YOU SEED First, know why the patch is bare
Seed won’t fix a patch whose cause is still active. Spend two minutes diagnosing before you spend an afternoon seeding.
- Pull at the dead grassIf it lifts like a carpet and you find fat white C-shaped grubs underneath, that’s grub damage — treat the cause first (see the grub guide), then reseed.
- Check for shade and trafficGrass needs roughly 4+ hours of sun. A patch under a maple that dies every year wants a shade-tolerant fescue mix, mulch, or a garden bed — not another round of sun-loving seed.
- Look at the soilHard, pale, compacted clay grows nothing well. Plan to aerate or scarify the patch and work in compost as part of the repair.
- Rule out salt and spillsPatches along the driveway or street that die every spring are usually road-salt damage — flush the soil with water in spring and reseed; a gypsum application is sometimes used for salt-affected soil by the curb.
THE METHOD Overseeding, step by step
Best window: late August to mid-September. Second choice: late April to May, with more watering discipline required.
- Mow the area short and rake hardCut the patch and its edges lower than usual, then rake vigorously to strip out dead grass and thatch until you can see soil. Seed must land on soil, not on a thatch mattress.
- Loosen the top centimetreScratch the exposed soil with a stiff rake or garden cultivator so it’s rough and crumbly. On compacted patches, a core aerator (rented, or a manual one for small areas) makes a real difference.
- Spread a thin layer of topsoil or compostAbout 0.5–1 cm over the patch — it gives seed a moisture-holding bed and feeds soil life. On Durham clay this step is not optional decoration; it’s the difference between sprouting and sulking.
- Sow seed generously and rake it inUse a quality Ontario mix (bluegrass / perennial ryegrass / fescue). Spread at the bag’s overseeding rate, then rake lightly so most seed disappears into the soil surface. Seed sitting visible on top mostly feeds birds.
- Press for seed-to-soil contactWalk the patch with flat shoes or roll it. Every seed needs to be touching moist soil on most of its surface to germinate — this contact is the whole game.
- Water lightly, then keep it damp for 2–3 weeksFirst watering: gentle, just to settle everything. After that, the seeded area must never fully dry out until seedlings are 5 cm tall — in September that may mean a light sprinkle once a day; in a dry May, two or three. Then taper to deep, infrequent watering.
- Keep off it, and mow high when it’s readyFirst mow when new grass reaches about 9–10 cm, with a sharp blade, back at the normal 7.5–9 cm height. Keep feet and dogs off until after that first cut.
WATCH OUT Common mistakes
- Seeding on top of thatch without rakingThe #1 failure. Seed on thatch germinates into air and dies at the first dry afternoon.
- One heavy watering, then forgetting itSeed that swells, sprouts, and then dries out dies — it can’t pause and restart. Little and often for three weeks.
- Seeding in June or JulyHeat, drought, and crabgrass pressure beat new seedlings almost every time. If it’s summer, plan the repair for late August instead.
- Using last year’s leftover seedOld seed loses germination every year, especially stored in a hot garage. Fresh seed is cheap insurance; do a quick germination test on a wet paper towel if you’re unsure.
Good to know
Why fall wins: soil is warm from summer (seed germinates fast), nights are cool (seedlings don’t stress), fall rains help with watering, and the crabgrass that plagues spring seeding is dying instead of sprouting. A patch seeded September 1st usually looks better by Thanksgiving than a patch seeded May 1st looks by July.