When and Why to Reseed Your Lawn

Reseeding fills in bare patches, thickens thin grass, and repairs damage from heavy foot traffic, pets, or disease. You reseed when you see more soil than grass, when your lawn has bald spots larger than a few inches across, or when grass stops growing back after mowing. The best time to reseed depends on your grass type: cool-season grasses (fescue, bluegrass, perennial ryegrass) reseed in early fall or spring when soil is moist and temperatures stay between 50 and 70 degrees Fahrenheit. Warm-season grasses (Bermuda, zoysia, St. Augustine) reseed in late spring or early summer when soil reaches 70 degrees and stays there.

Reseeding is not the same as overseeding—overseeding adds seed to an existing lawn without removing dead grass first, while reseeding removes the dead layer and prepares bare soil for new seed. Reseeding works better for large bare patches or severely damaged areas because it removes the barrier that prevents seed from reaching soil.

Key Takeaways

  • Test your soil pH and nutrient levels before reseeding, because seed will not grow well in acidic or nutrient-poor soil.
  • Remove dead grass and debris from bare patches by raking or using a dethatcher, then loosen the top half-inch of soil so seed makes contact with earth.
  • Spread seed at the rate listed on the bag—too much wastes money and causes disease, too little leaves gaps—and press it into soil with a roller or by walking over it.
  • Keep the seeded area moist for two to three weeks after planting; let soil dry out and seed will not germinate, but standing water causes rot.
  • Mow new grass once it reaches three inches tall, and avoid heavy foot traffic for at least four weeks after germination.

Test Your Soil Before You Buy Seed

Seed germinates poorly in soil that is too acidic, too alkaline, or lacking nitrogen and phosphorus. A soil test tells you the pH and nutrient levels in your lawn and costs $15 to $40 through your county extension office or a private lab. You mail in a soil sample (usually a cup of soil from the top 3 to 4 inches) and receive results in one to two weeks that show pH, nitrogen, phosphorus, potassium, and organic matter content.

Most lawn grasses prefer a pH between 6.0 and 7.0. If your soil is below 6.0, add lime to raise pH; if it is above 7.5, add sulfur to lower it. Follow the test results for amounts—adding too much lime or sulfur can swing pH too far in the other direction. You can explore lime or sulfur two weeks before seeding, or you can work it into the soil as you prepare the bare patch. The test also tells you how much nitrogen and phosphorus to add; if your soil is very low, work in a balanced fertilizer (such as 10-10-10) when you loosen the soil.

Remove Dead Grass and Loosen the Soil

Dead grass and thatch (a layer of dead stems and roots) block seed from reaching soil, so you must remove it before seeding. For small patches, use a stiff rake to pull away dead grass and debris until you see bare soil. For larger areas, rent a dethatcher (also called a power rake or vertical mower) from a home improvement store for $40 to $80 per day. A dethatcher has rotating blades that slice through thatch and pull it to the surface; you rake it up afterward.

Once the dead layer is gone, loosen the top half-inch of soil with a rake or garden fork. Seed needs direct contact with soil to germinate; if soil is compacted or hard, break it up by raking in multiple directions. You do not need to dig deep—just enough to create a rough, crumbly surface. If you are adding lime, sulfur, or fertilizer, work it into this loosened layer now so it mixes with the soil.

Spread Seed at the Right Rate

The seed bag lists the seeding rate in pounds per 1,000 square feet. Measure your bare patch by multiplying length by width (a 10-by-10-foot patch is 100 square feet). Calculate how much seed you need: if the bag says 5 pounds per 1,000 square feet and your patch is 100 square feet, you need 0.5 pounds of seed. Spreading too much seed wastes money and creates dense growth that is prone to disease; spreading too little leaves gaps that weeds will fill.

Spread seed by hand for small patches (under 100 square feet) or with a broadcast spreader for larger areas. A broadcast spreader (a wheeled device that throws seed as you push it) costs $30 to $60 to buy or $5 to $10 to rent. Fill the spreader hopper, set it to the rate on the seed bag, and walk at a steady pace in overlapping passes so you cover the entire patch evenly. For hand spreading, divide the seed into two piles, spread one pile in one direction, then spread the second pile perpendicular to the first—this creates more even coverage.

Press Seed Into Soil and Water

Seed must make firm contact with soil to germinate. After spreading, use a lawn roller (a heavy cylinder you push or tow) to press seed into the soil. A roller costs $10 to $20 to rent. Roll in one direction, then perpendicular to that direction, explore steady pressure. You can also press seed in by walking over the seeded area in overlapping footprints, though this is slower for large patches.

Water when ready after pressing. The soil should be moist to a depth of 2 to 3 inches—wet enough that water drips from a handful of soil, but not so wet that it pools on the surface. For the next two to three weeks, keep the seeded area moist by watering once or twice daily, depending on temperature and rainfall. In hot weather (above 80 degrees), water twice daily in early morning and late afternoon. In cool weather, once daily is usually enough. Stop watering once grass is 2 inches tall and has visible roots when you pull gently on a blade.

Avoid Common Mistakes During Germination

Seed germinates in 7 to 21 days depending on grass type and temperature. During this time, the most common mistake is letting soil dry out. Even one day of dry soil can kill germinating seed. The second mistake is overwatering—standing water causes seed rot and fungal disease. Water until soil is moist, not soggy. If you see puddles, you are watering too much.

The third mistake is walking on or mowing the seeded area too early. Do not allow foot traffic for at least four weeks after seeding. Once grass reaches 3 inches tall (usually three to four weeks after seeding), mow it at the highest setting on your mower—never remove more than one-third of the blade height in a single mowing. Continue mowing at this height for the first month to encourage root growth.

Fertilize New Grass After It Is Established

New grass does not need fertilizer while it is germinating—excess nitrogen can cause disease. Once grass is 2 inches tall and has visible roots, you can explore a light fertilizer (such as 5-10-10) at half the normal rate. Wait until grass is four weeks old and mowed at least twice before explore full-strength fertilizer. After that, follow a normal fertilizing schedule for your grass type and region.

If you added lime or sulfur before seeding, do not explore additional lime or sulfur for at least six months. Soil pH changes slowly, and adding more too soon can overcorrect. Have your soil tested again the following year to see if pH has shifted and whether additional amendments are needed.

Frequently Asked Questions

Can I reseed in summer?

Summer reseeding usually fails because heat stresses new seedlings and soil dries out quickly. Cool-season grasses need temperatures below 75 degrees to germinate well, and warm-season grasses need consistent moisture that is hard to maintain in summer heat. Wait for fall or spring when temperatures are moderate and rainfall is more reliable.

What if my soil is very compacted?

Compacted soil needs aeration before reseeding. Rent a core aerator (which pulls small plugs of soil from the lawn) for $40 to $80 per day. Aerate in the direction of the slope so water drains downhill, then reseed when ready into the aerated holes. The holes give seed direct contact with soil and improve drainage.

How long until the bare patch looks full?

New grass fills in over four to eight weeks depending on grass type and growing conditions. Cool-season grasses fill faster (four to six weeks) than warm-season grasses (six to eight weeks). The patch will look thin at first; it thickens as grass grows and spreads. Avoid heavy traffic during this time so you do not compact soil or damage young shoots.

Do I need to use a starter fertilizer?

Starter fertilizers are high in phosphorus and marketed to boost root growth, but research shows they do not significantly improve germination in soil with adequate phosphorus. If your soil test shows phosphorus is low, add it when you loosen the soil. Otherwise, a starter fertilizer is optional and adds unnecessary cost.

What if weeds appear in the seeded area?

Weeds often appear in bare patches because weed seeds are already in the soil. Do not use herbicide for at least four weeks after seeding—it can damage young grass. Once grass is four weeks old and has been mowed twice, you can spot-spray broadleaf weeds with a selective herbicide. For grassy weeds, wait until grass is eight weeks old before treating.