Overseeding — as part of a comprehensive, proactive plan — keeps lawns looking great. Whether you’re tending your lawn for the first time or have years of experience, overseeding can improve your results in the Cedar Rapids, Iowa City, Des Moines, Waterloo, and Quad Cities, Iowa areas.
Overseeding is simply spreading grass seed over an existing lawn. Done right, it’s a simple process that gets the most from your seed and labor. As grasses mature, thinning is normal — especially if you enjoy your lawn and use it often. Overseeding keeps your lawn lush and green while also strong and healthy, without starting over from scratch.
The processes for overseeding the lawn are basically the same no matter where you live, but goals and timing vary based on geographic location and the type of grass grown. For success with overseeding your lawn in Iowa, follow this basic guide:
When is the best time to sow grass seed in Iowa?
Late summer (mid-August to mid-September) is the best time to overseed your lawn in Iowa. Late summer seeding has several advantages over spring seeding. The seeds of cool-season grasses that are best grown in Iowa germinate quickly in the warm soil of late summer.
Once the seeds germinate, the warm days and cool nights of early fall promote rapid turfgrass growth. The growing grass also has less competition from weeds, as few weed seeds germinate in fall.
What Type of Grass Grows Best in Iowa?
Kentucky bluegrass – This is the most popular turfgrass of all cool-season grasses in the upper Midwest region. It is a dark-green, medium-textured turf. The leaf blades have a boat-shaped tip; the sides of the blades are parallel, giving a stiff appearance. This species spreads by underground rhizomes that can self-repair injured, worn, or damaged spots. It also produces a dense turf.
Kentucky bluegrass is great for Iowa because it can tolerate cold winters but has a relatively low tolerance for heat and is only moderately drought tolerant. During the summer months, if stressed for water, Kentucky bluegrass can go dormant. It has moderate wear tolerance, recovering quickly from some abuse.
Kentucky bluegrass is a cool-season grass that grows best during the fall, winter, and spring months when temperatures are cool. Its growth slows during the warm summer months. Kentucky bluegrass prefers full sun, but will tolerate some shade. When stressed by temperatures, lack of water, or poor soils, Kentucky bluegrass can be susceptible to disease and weed invasion. For a more disease resistant turf that offers good color and year-round performance, Kentucky bluegrass is often mixed with perennial ryegrass. Usually, two or more cultivars of each species are used and it is recommended that at least 15% of the mixture is perennial ryegrass.
Perennial ryegrass – A fine-textured, rich green grass with the leaf folded in the bud. Leaf margins are parallel, the back of the leaf is shiny, and the tips of the leaf blades are tapered. Ryegrass may form clumps where marginally adapted. There are no rhizomes or stolons. Perennial ryegrass has a bunchgrass-type growth habit.
Perennial ryegrass has a moderately low tolerance for heat, shade, and drought and a high tolerance for cold temperatures.
Perennial ryegrass is a very competitive cool-season grass. It prefers full sun but will tolerate partial shade. Perennial ryegrass has the highest wear-tolerance of any cool-season grass and can tolerate high traffic. It is often used around homes, schools, and parks. Its rapid emergence helps to suppress weeds. For a more traffic and disease-resistant turf, it is often mixed with Kentucky bluegrass.
How do I overseed an existing lawn?
For successful overseeding, you need to make sure that the seeds have sufficient contact with the soil. Therefore, to reduce the competition from the established grass, mow the lawn at a height of 1½ to 2 inches before you begin overseeding. Core aerators, vertical mowers, and slit seeders can be used to ensure good seed-to-soil contact.
Core aerators are machines with hollow metal tubes or tines. They remove plugs of soil when run over the lawn. Apply the grass seed with a drop seeder. Afterward, you can drag the area with a piece of chain link fence or drag mat to break up the soil cores and mix the seed into the soil.
Another great method for overseeding is to prepare the lawn with a vertical mower. When run over the lawn, the knife-like blades of the vertical mower slice through the thatch and penetrate into the upper 1/4 to 1/2 inch of soil. One or two passes should be sufficient. Afterward, remove any debris from the lawn. Sow grass seed over the lawn with a drop seeder. Work the seed into the soil by again going over the site with the vertical mower.
Large areas also can be overseeded with a slit seeder. A slit seeder makes small grooves in the soil and deposits the seed directly into the slits.
Core aerators, vertical mowers, and slit seeders can be rented at garden centers and rental agencies. For those who would rather not do the work themselves, contact Lawn-Tek for a custom quote… We’re happy to help!