Establishing a new lawn requires careful planning and hard work. However, it is time well spent. The effort devoted to site preparation and turf establishment will be reflected in the quality of the turf for many years.
When to Seed | Selecting the Right Grass Species | Preparing the Site | Spread the Seed | Watering & Mulching | When do I Mow? | Weed Control | More Information
When to Seed a Lawn
Late Summer/Early Fall is Best
The best time to establish a lawn from seed is from mid-August to mid-September. Late summer planting has several advantages over spring seeding. The cool-season grasses will germinate quickly in the warm soil of late summer. The warm fall days and cool nights promote rapid turf growth. Also, few weed species germinate in the fall, so there is little weed competition.
Dormant Seeding
Dormant seeding is an option if the preferred late summer seeding window is missed. Seed needs to be sown after turf growth has stopped but before the ground freezes, typically from late November through early December (and as late as early February if winter conditions allow it). Air temperatures should remain below 30°F to 40°F, and soil temperatures should be 40°F or lower to prevent germination before winter. Good seed-to-soil contact is essential. When properly timed, seed remains dormant through winter and germinates as soils warm in spring, often resulting in earlier establishment than spring seeding. However, success depends on winter conditions, and some seed loss from cold injury, erosion, or wildlife is common. As a result, additional overseeding in spring may be needed to fill thin areas.
Spring Seeding
Establishment from seed in the spring (early April to mid-May) is possible when irrigation is available. However, lawns established in spring are often infested with annual weeds unless preventive measures are taken. Some pre-emergent herbicides, such as mesotrione, can be applied to the area during spring establishment to reduce unwanted weeds. Most preemergent herbicides kill the seeds of cool-season lawn grasses and cannot be used at seeding time. Products like Mesotrione are the only exceptions. Do not use crabgrass preventer or other pre-emergent herbicides unless they are labeled for new seedlings.
Summer Seeding
Seeding from late May to mid-August is extremely difficult and usually unsuccessful.
Selecting the Appropriate Species of Turfgrass
Select turfgrass based on site conditions. For sunny areas with 6+ hours of direct sun, use Kentucky bluegrass and choose a mix with 2-3 varieties. Fine-leaf fescues (creeping red, hard, chewings, and sheep fescue) are best for shade, while perennial ryegrass is commonly added for quick germination and establishment.
- Sunny sites: 80-90% Kentucky bluegrass, 10-20% perennial ryegrass.
- Sun and shade: 50-60% Kentucky bluegrass, 30-40% fine-leaf fescue, 10% perennial ryegrass.
- Heavy shade (<2 hours direct sun): 100% fine-leaf fescue, though non-turf alternatives are often a better choice. Learn more in this article: Growing Grass in Shady Areas.
Purchase a high-quality seed mix and avoid products with large amounts of annual ryegrass, weed seed, or inert material. While premium seed costs more, it typically results in fewer problems.
Learn more in this publication: Selecting a Grass Species for Iowa Lawns.
Preparing the Site
Begin by establishing the rough grade: remove construction debris, fill low spots, level high areas, and ensure the ground slopes away from the house foundation, driveway, and sidewalks. Complete rough grading well before seeding to allow the soil to settle.
A minimum of 4-6 inches of quality soil is needed for lawn establishment. If necessary, add weed-free topsoil or organic matter and incorporate these materials, along with fertilizer, into the top 6 inches of soil, typically by tilling. Avoid tilling wet soil. If a handful of soil holds its shape when pressed, it is too wet; if it crumbles, it is ready to till. Do not over-till, as this damages soil structure.
When finished, rake the area to create the final grade.
Fertilization
Fertilization at seeding is critical because it is the only opportunity to incorporate soil amendments and fertilizer into the root zone. Use a soil test to determine fertility needs and apply the recommended fertilizer before incorporating it into the soil. If no soil test is available, apply 5 pounds of a 20-5-10 (or similar) fertilizer per 1,000 square feet and till it in.
The final soil preparation step is hand-raking, which also provides the last chance to establish the final grade. Immediately before seeding, apply a phosphorus-rich starter fertilizer. Additional fertilizer may be needed 3-4 weeks after germination, when the grass reaches 1 to 1.5 inches tall. Learn more in this publication: Lawn Fertilization.
Spreading Seed
To achieve uniform seed distribution, use a drop-type seeder. Sow half the seed in one direction. Apply the remaining half at right angles to the first application. After sowing the seed, lightly rake or drag the area. The seed should be covered to a depth of 1/8 to 1/4 inch. While not necessary, you can roll the area lightly to ensure good contact between the seed and soil.
Watering & Mulching
Mulch newly seeded areas with clean, weed-free straw to conserve moisture and reduce erosion and soil crusting. Apply only enough straw to leave about 50% of the soil visible, typically one bale per 1,000 square feet, as excessive mulch can smother seedlings. Erosion-control mats or blankets are excellent alternatives for steep slopes and other erosion-prone areas.
After mulching, water to moisten the top 1 inch of soil. Because grass seedlings are highly susceptible to drying out, keep the soil surface consistently moist, watering only as needed to avoid overwatering and runoff. During germination, irrigate lightly and frequently to keep the upper inch of soil continuously moist, usually requiring daily watering and sometimes several times a day in sunny, windy conditions. Once seedlings reach 2 inches tall, water less often but more deeply.
When to Start Mowing
Mow new grass when it reaches 3 inches tall using a sharp mower blade. Maintain a mowing height of 2 to 2.5 inches to encourage spreading and thickening. Do not allow the grass to become excessively tall before the first mowing. If it does, mow in stages to prevent scalping and avoid removing more than one-third of the grass tissue at a time.
Broadleaf Weed Control
After establishing a new lawn, broadleaf weeds often germinate alongside grass seedlings. Most can be controlled with a broad-spectrum selective broadleaf herbicide, such as 2,4-D, once the turf is established. Herbicides can be safely applied after the lawn has been mowed 3 to 4 times. Learn more in this publication: Weed Control in Home Lawns.