Seeding rate by grass type
How much seed to buy per 1,000 sq ft. New lawns need roughly twice the rate of overseeding into an existing stand. Buy the bag size that matches your lawn area, not your wallet.
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| Grass | Season | New lawn (per 1,000 sq ft) | Overseed (per 1,000 sq ft) |
|---|---|---|---|
| Kentucky Bluegrass | Cool | 2–3 lb | 1–1.5 lb |
| Tall Fescue | Cool | 6–8 lb | 3–4 lb |
| Fine Fescue | Cool | 4–5 lb | 2–3 lb |
| Perennial Ryegrass | Cool | 6–8 lb | 3–4 lb |
| Bermudagrass | Warm | 1–2 lb | 0.5–1 lb |
| Zoysiagrass | Warm | 1–2 lb | 0.5–1 lb |
| Centipede | Warm | 0.25–0.5 lb | 0.25–0.5 lb |
Rates from university extension services. Multiply by your lawn size in 1,000s — a 5,000 sq ft Tall Fescue overseed needs about 5–10 lb of seed.
Optimal vs. acceptable seeding windows
The calculator gives you both. Optimal is the stretch where germination is fastest, weed pressure is lowest, and the seedlings have time to harden off before stress. Acceptable still works — it just takes longer or needs more babying.
For cool-season grasses (Kentucky Bluegrass, Tall Fescue, Ryegrass, Fine Fescue), the optimal window is 60 to 45 days before your first fall frost. Soil is still warm, air is cooling, and crabgrass has stopped germinating. Spring works as a backup when fall got missed, but it's a fight against summer heat and crabgrass.
For warm-season grasses (Bermuda, Zoysia, Centipede, Buffalograss), the optimal window opens after your last spring frost and stays open while soil temps hold above 65–70°F. Fall seeding doesn't work — seedlings can't establish before dormancy.
If you're in the acceptable window, expect germination 3–7 days slower than the optimal range, and plan to water more carefully. If you're past too-late, wait for the next window or use sod for an immediate result.
Soil temperature trumps the calendar
Calendar dates are an approximation. The real signal is soil temperature at 2–4 inches deep. Cool-season grasses germinate fastest at 50–65°F soil; warm-season grasses need 65–70°F+. Check your local soil temp before you spread seed — a warm spring or cold fall can shift the window by two weeks in either direction.
- Cool-season seed in 70°F+ soil burns the seedling roots before establishment.
- Warm-season seed in 60°F soil germinates extremely slowly, if at all.
- Soil temp is also the trigger for crabgrass germination (~55°F) — overlap with cool-season seeding is the #1 reason spring lawns fail.