Dates are the standard cadence — germination speed varies by grass (rye ~7 days, fescue ~14, bluegrass up to 21+). No pre-emergent anywhere in this timeline unless it's labeled seeding-safe.
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The timeline, and why each gap exists
spray −21 days · buy −7 · SEED day 0 · daily water → +18 first mow ≈ +25 · first regular feed ≈ +49
The three-week gap before seeding lets weed spray fully clear (labels vary — check yours). The 2–3 weeks of daily light watering is the non-negotiable: seed that dries mid-germination dies, and there are no partial credits. The mow and feed dates wait for roots — mowing too early uproots seedlings the tug test would have saved.
Seed day itself
Mow at 2 inches and bag the clippings, open the soil (cores or a hard rake — seed on top of thatch grows nothing), spread the seed calculator's overseeding rate half in each direction, then starter fertilizer per the fertilizer calculator. Not sure the ground needs opening? The aerate-or-dethatch diagnostic settles it — and aeration day and seed day should be the same day.
Watering the nursery
Until germination: light and daily (twice daily in heat) — the top half-inch stays moist, never soggy. After germination: taper toward the normal deep-and-infrequent schedule over two weeks. This is the only time in lawn care that daily sprinkles are correct; enjoy the exception.
Frequently asked questions
When should I overseed my lawn?
Cool-season lawns (fescue, bluegrass, rye): 6–8 weeks before your first frost — early fall, when soil is warm, air is cooling, and weeds are winding down. Spring works but the seedlings face summer young. Warm-season lawns spread by runners and rarely need overseeding at all — thin bermuda usually needs feeding, not seed.
What's the right order of steps for overseeding?
Mow low and bag → rake or core-aerate (seed MUST touch soil) → spread seed → starter fertilizer → water lightly every day until germination, then taper. Every failed overseed skipped one of those — usually the soil contact or the daily watering.
Can I use weed killer when overseeding?
Not near it. Post-emergent sprays need to finish 2–4 weeks BEFORE seeding (check your label), and most pre-emergents block your grass seed for 8–16 weeks. The planner above builds these blackout windows into your timeline — weed control ends, then seeding begins.
When can I mow new grass?
When it reaches about 3 inches or resists a gentle tug — typically 3–4 weeks after germination. Sharp blade, remove only a third, and skip the striping ambitions for a month. First regular fertilizing lands 6–8 weeks after seeding, after the starter feed runs out.