1. Watch the soil temperatures
If it’s too cold, grass seed won’t germinate. If it’s too hot, the baby grass seeds will pop up, then quickly fry. Generally, you should plant grass seed as early as possible in the spring, says Waltz. For southern climates, that may be as early as February; in the north, that’s after your last snowfall and into April or May but can vary depending on the weather. However, generally it’s better to put out seed too early than too late in the season. Most grass seed germinates when soil temperatures are around 55 to 60 degrees F.
2. Figure out what kind of grass you have
You’ll want to plant the same type to avoid a patchy appearance in the lawn. In general, there are two main types: Warm season grasses grow during the warm times of year, roughly May to September; they’re mostly found in the South. Cool season grasses grow during cooler times of year, typically from December to early February; they’re mostly found in the north and upper third of the country. In transitional parts of the country such as the Mid-Atlantic, you may have both types, says Waltz. If you aren’t sure about what you have, check with your university coop extension service (find yours here), which can tell you what species is in your lawn.
3. Prepare the soil
Rake up the bare area and get rid of any sparse grass, sticks, weeds or stones. Loosen the soil a few inches deep; four inches below the surface is best, if you can manage it, with a tiller or garden shovel. Rake out and level the area, then pat it down so it’s firm but you can still push a finger into the surface, says Waltz.
4. Sow your grass seed
Keep this in mind: You want the seeds to make good contact with the soil for improved germination rates. Sprinkle seed on the bare area, lightly working in into the first 1/8-inch of soil. Pat down the surface. It’s fine to mulch lightly with straw, if you like, or to cover seeds with a light sprinkle of soil. But don’t bury seeds more than 1/8-inch deep or they don’t do well, says Waltz.
5. Keep the area damp
Water the area and keep it moist, not sopping wet or soupy. It can take a few days to a few weeks for germination, depending on the type of seed and weather conditions. Don’t count on rain to do all the work; you’ll need to check the area daily to ensure it remains moist. It’s especially important to maintain moisture once the seeds start to swell because you can’t stop the process, and grass seedlings are susceptible to drying out quickly (and dying!).
6. Delay mowing
Once the grass pops up, don’t mow until it reaches several inches tall; check the recommended mowing height for your species—and don’t mow while the ground is wet so you make tire ruts. And one final (vitally important!) word of wisdom: If you’ve put down a pre-emergent herbicide to prevent weeds from germinating, it’s too late to plant grass seed. Pre-emergent products suppress everything from germinating, so you’ll have to wait until fall to seed.