Tips on how to seed your lawn in fall

“There are some bare patches on my lawn. Is this a good time to sow seeds?”

– Layton Hopkins, Evanston

This is a good time of year to seed a lawn to give the grass a good chance to settle before winter.

You can expect fewer problems with broadleaf weeds that become established after sowing at this time of year. Some weeds may germinate, but they should be easy to control later once the new weed is established. I’ve seen lawns with a large weed seed bank that required extensive weed control, but that’s usually the exception.

Without proper site preparation, most lawn repair projects done by seeding fail. First: Remove dead grass, weeds or thatch from the area to be seeded. It is important that the grass seed is in contact with the ground. The soil also needs to be loosened with a cultivator or a spade to create a good seedbed for the grass to take root in. Large areas can be processed. Spreading grass seed on compacted ground (as is often done) does not work. Once the soil is cultivated, you may need to add a small amount of topsoil to even out the area and improve growing conditions for grass seed germination.

Choose a quality grass seed mix that is appropriate for the amount of sunlight your lawn will receive. Blends include various types of bluegrass, as well as other grasses such as perennial ryegrass, hard fescue, and chewing fescue. Use a sun and shade grass seed mix when sowing in sunny and shaded areas to get a more even color throughout the lawn. Gently rake in the grass seed with a leaf rake and fertilize lightly with compost or a commercial seed booster. These are biodegradable pellets designed to expand and hold water. Some of these products also have a starter fertilizer. I prefer not to use peat for top dressing grass seed as once it gets dry it tends to repel water.

Bluegrass takes about two weeks to germinate, so watch your watering carefully to keep the seed moist during this time. This requires frequent light watering of at least once a day and twice a day when the weather is hot or windy. As the grass begins to grow, you can water less frequently and deeper to encourage a deeper root system. Allowing the grass seed to dry out for the first few weeks can greatly reduce the percentage of germination.

Mow the grass when it grows enough to require it. If the ground is soft, allow the ground to dry out a little before mowing to avoid ruts from the mower wheels. You don’t need to fertilize the new lawn this fall.

For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at [email protected]. Tim Johnson is Senior Director of Horticulture at the Chicago Botanic Garden.