When should you overseed a lawn?
Written by
Julia Anderson
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.A process called overseeding helps rejuvenate thinning lawns by filling in bare patches and increasing the overall thickness of the turf. Timing is critical for success and can largely be determined by the type of grass seed sown according to soil temperatures associated with each season. Cool-season grass should be overseeded in early spring or early fall, while warm-season grass should be overseeded mid-spring. Every effort should be made to prepare the soil to optimize germination rates.
Soil Readiness
- Aerate compacted areas allowing seed-to-soil contact
- Top-dress with 1/4 inch compost for nutrients
- Verify soil temperature matches grass requirements
Seed Selection
- Choose varieties matching existing lawn composition
- Opt for coated seeds improving moisture retention
- Blend drought-tolerant types for resilient coverage
Grass varieties that grow in cooler seasons, such as Kentucky Bluegrass, need soil temperatures of 50-65°F to germinate. This germination typically occurs approximately 6 weeks before the first frost date. Warm-season grasses, such as Bermudagrass, thrive in soil temperatures of 65-70°F, which is best achieved in early spring. I target the time of overseeding to when forsythia bloom in my cool-season lawns.
Maintain soil moisture at a steady level without overwatering. Water the newly seeded areas lightly twice a day. Use mulch mats on slopes to prevent erosion. Reduce foot traffic while the grass is germinating. I always fence off areas temporarily from foot traffic to avoid trampling, as the grass is germinating - this is an important step for the grass to establish itself. I usually wait until the grass is 3 inches in height before I take down the fencing.
Once the seedlings have become established, mow carefully. Please wait until the grass reaches at least 4 inches in height before the first mowing. Use sharp blades set at the highest settings available. Follow with an application of starter fertilizer, but apply it only after the second mowing has taken place. Proper overseeding can yield noticeably thicker turf within six weeks.
Completely transforming patchy lawns can depend on timing. Cool-season grasses, overseeded in the fall, develop deep roots before winter. Warm-season grasses develop quickly in the warmth of spring. Following these steps will produce resilient turf that requires less maintenance in the long run.
Read the full article: How to Care for Lawn: Beginner's Guide
