Best Time to Overseed the Lawn

I want to overseed my Chicago area lawn. Is it better to do it in the spring or fall? What steps do I need to take?

The best time to seed northern lawns is mid August through mid September. The next best time is early to mid May. Overseeding can be done at either time. Small areas can be handled best by mixing the grass seed with topsoil. Sprinkle this mix over the soil surface. Keep it moist until the seed germinates.

Overseeding large areas requires more effort and some equipment for best results. Cut the grass short and scratch the soil surface to insure good seed soil contact. An iron rake will work for small yards and give you a great upper body workout at the same time.

Dethatching machines or vertical mowers can be used to remove thatch and loosen the soil surface before seeding. A core aerator will help open up thatch layers and insure good seed-to-soil contact with much less stress on the lawn. Spread the grass seed over the lawn. Or use a slit seeder. This machine slices the soil and spreads the seed in one operation.

Keep the soil surface moist and grass a little shorter while waiting for the seed to germinate. Once the seed sprouts water thoroughly but less frequently and raise the mowing height back to 2 1/2 to 4 inches. A low nitrogen slow release fertilizer can be applied to the lawn prior to overseeding.

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