Seeding a lawn is cheap compared to sod — and unforgiving of bad timing. Get the calendar and the rate right, and grass seed is the best value in landscaping. Get either wrong and birds eat your budget.
The calendar
Cool-season grasses — Kentucky bluegrass, tall and fine fescues, perennial ryegrass — germinate best in warm soil under cooling air: late summer through early fall is prime across the northern US. Fall-seeded lawns establish roots before winter and hit spring running with almost no weed competition. Spring is the fallback (soil must pass ~50 °F), accepting crabgrass season as the price.
Warm-season grasses — bermuda, zoysia, centipede, bahia — want genuinely warm soil: late spring, after nights hold above 65 °F. Seeding them early just rots the seed.
The rates
| Grass | New lawn (lb / 1,000 sq ft) | Overseeding |
|---|---|---|
| Kentucky bluegrass | 2–3 | ½ rate |
| Tall fescue | 6–8 | ½ rate |
| Fine fescue | 4–5 | ½ rate |
| Perennial ryegrass | 5–7 | ½ rate |
| Bermuda (hulled) | 1–2 | ½ rate |
The grass seed calculator applies these rates to your lawn's area and tells you both the weight and the bag-size you'll actually find at the store. Overseeding uses about half the new-lawn rate — you're thickening a stand, not planting bare soil.
The watering schedule that makes or breaks it
- Days 0–14: light watering once or twice daily — the top inch of soil stays constantly damp, like a wrung sponge. This is the phase where most lawns fail; 20 minutes of neglect on a hot day kills germinating seed.
- Weeks 2–4: as sprouts show, ease to every other day, a bit deeper.
- Weeks 4–8: shift to twice-weekly, deep soakings — teaching roots to chase water down.
- First mow: at 3–3.5 inches, never cutting more than a third. Traffic stays light for 6–8 weeks.
Seed-quality quick check
Every bag's tag lists purity and germination. Quality seed runs 95%+ / 85%+; bargain racks sell 75/70 mixes diluted with crop seed and coating. The published rates above assume decent seed — with cheap seed, expect to overbuy modestly and get a weedier stand anyway. The tag is 30 seconds of reading that predicts your whole lawn.