Will Grass Seed Choke Out Weeds?

When to Consider Renovation

• Homeowners should consider renovating a lawn when it has large areas of dead or thinning grass, when weeds have overtaken it or when it no longer responds to water and fertilizer applications. It's important to put a lot of thought and planning into your renovation. Seeds must have good contact with the soil for germination. According to Cornell University, late summer into early fall is the prime time for planting new seed.

Lawn Issues

• Try to determine why the current lawn is doing poorly so you can address it with the renovation. For example, sparse growth may be caused by insect damage, fungus, disease, compaction or drought. Broadleafed weeds such as dandelion and ground ivy often establish themselves at this point. The lawn also becomes more susceptible to crabgrass. A lawn that feels spongy when you walk on it may have excessive thatch, a layer of dead organic matter that forms above the soil surface. Thatch makes it hard for water and fertilizer to reach the roots, and seeds spread over the thatch have a poor germination rate.

Dealing With Weeds

• Although it would be nice if grass seedlings were vigorous enough to choke out weeds, this simply isn't the case. Apply a non-selective herbicide such as glyphosate to kill the existing vegetation in the area you wish to renovate. Glyphosate is sold as Roundup, though generic formulations exist. After the existing vegetation is killed off, use a rotary tiller to prepare the soil for the new seed. Amend the soil if necessary at this point -- it should have 4 inches of topsoil.

New Grass Seed

• Water the area to moisten the soil and then apply fertilizer to your prepared soil. The University of Minnesota recommends applying a fertilizer that has 1/2 lb. of nitrogen per 1,000 square feet. Then apply the seed. You may sow the seed by hand for small areas. For large areas, use a rotary spreader or drop spreader or rent a slit seeder to accomplish the job. After seeding, keep the area well watered. Pull any weeds that may pop up to reduce the competition for water and nutrients. Mow the lawn once the blades of grass grow 3 to 4 inches high. Once you establish a lush, thick lawn, it will crowd out weeds and require less maintenance.