How often should you overseed a lawn?
Updated July 2026
Overseed a cool-season lawn once a year in early fall, and a warm-season lawn in late spring as it comes out of dormancy. A dense, weed-free lawn can stretch to every 2–3 years, but thin turf earns a yearly pass. The point is to keep the stand thick: grass is the best weed control there is, and every bare patch you leave open in fall is real estate that crabgrass and broadleaf weeds will claim by summer.
What changes the interval
| Your situation | Interval | Why |
|---|---|---|
| Cool-season lawn | Early fall (Aug-Sept) | Warm soil, cool air, and fewer weeds |
| Warm-season lawn, winter color | Fall with ryegrass | Ryegrass greens dormant Bermuda over winter |
| Warm-season lawn repair | Late spring | Seed when the grass is actively growing |
| Thin or patchy after summer | Every year | Fill the voids before weeds claim them |
| Dense, healthy, weed-free turf | Every 2–3 years | Less need when the stand is already thick |
| New sod, first two years | Skip it | Let the sod knit in before adding seed |
The cost of skipping it
What skipping it costs: every bare or thin patch you leave is an open invitation to crabgrass and broadleaf weeds, which colonize open soil faster than desirable grass does. A thin lawn also erodes on slopes and scalps easily under the mower. Once weeds take a thin stand, winning it back is a multi-season chemical fight, versus a $40–80 bag of seed and one fall afternoon to keep the turf dense enough to crowd them out.
How to do it (2–3 hours · DIY with a spreader)
- Mow short, around 2 inches, and bag the clippings so the new seed can actually reach the soil.
- Dethatch or core-aerate first if the lawn is thatchy or compacted, because seed-to-soil contact is everything.
- Spread seed with a broadcast or drop spreader at the overseeding rate on the bag, often 4–6 lbs per 1,000 sq ft, about half the new-lawn rate.
- Rake lightly or drag a mat so the seed settles into the surface, and topdress thin spots with a little compost.
- Keep the top inch of soil moist with short daily waterings until germination (7–21 days), then taper to deeper, less frequent watering.
Knowing the interval is the easy half. OnOtto reminds you at the right interval, and it won't let you snooze it into next year. Tasks persist until they're done, and completing lawn overseeding schedules the next one automatically.
Put this on autopilot, free for 30 daysFrequently asked questions
Should I dethatch or aerate before overseeding?
If the lawn is thatchy or compacted, yes: seed germinates only where it touches soil, and a dead thatch mat or a hard, packed surface blocks that contact. Dethatch to clear the mat and core-aerate to open compacted soil, then broadcast seed right after so it drops into the openings. On a healthy, open lawn you can skip straight to spreading seed and topdressing the thin spots with compost.
How much seed do I use, and how do I water it?
Use the overseeding rate on the bag, usually around 4–6 lbs per 1,000 sq ft, roughly half the rate for a brand-new lawn. Then watering is everything: keep the top inch of soil consistently moist with short, light waterings once or twice a day until seedlings appear, which takes 7–21 days depending on grass type, then gradually shift to deeper, less frequent watering as the new grass roots in.
Can I overseed in spring instead of fall?
You can, but for cool-season grass fall is far better: warm soil, cool air, and fewer weeds give seedlings time to root before winter. Spring seeding collides with summer heat and crabgrass season, and most crabgrass preemergents also stop grass seed from sprouting, so you cannot do both in the same spot. If you must seed in spring, skip the preemergent that year; see crabgrass preemergent timing.
What seed should I use to overseed?
Match your existing grass and your climate: a quality cool-season blend of turf-type tall fescue, Kentucky bluegrass, and perennial ryegrass for northern lawns, or perennial ryegrass over dormant Bermuda for winter color in the South. Look for a low weed-seed percentage on the label and a variety suited to your sun exposure. Cheap contractor mixes often carry annual grasses and weed seed you will fight later.