Mid-August to mid-September is the best time to seed new lawns and overseed existing lawns in Iowa. Late summer seeding has several advantages over spring seeding. The seeds of cool-season grasses germinate quickly in the warm soil of late summer. 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.
Seeding and Overseeding Lawns
When purchasing grass seed, select a high quality seed mix that is best adapted to the site. Kentucky bluegrass is the best choice for sunny areas that receive at least 6 hours of direct sun each day. Choose a seed mix that contains at least 2 or 3 bluegrass varieties. Because Kentucky bluegrass is slow to establish from seed, perennial ryegrass is often included in bluegrass mixes to speed establishment. The fine-leaf fescues (creeping red fescue, hard fescue, chewings fescue, etc.) are the best grasses for shady locations. In lawns that contain sun and shade, select a seed mix that is approximately 60 percent Kentucky bluegrass, 30 percent fine-leaf fescue, and 10 percent perennial ryegrass. Kentucky bluegrass will be the dominant grass in the sunny areas while the fine-leaf fescues will thrive in the shaded portions of the lawn.
After seeding, keep the upper 1 inch of soil moist with frequent, light applications of water. The seeds of most turfgrasses should germinate in 2 to 3 weeks if the seedbed is kept uniformly moist. Gradually reduce the frequency of watering, but water more deeply, when the grass seedlings reach a height of 1 to 2 inches.