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 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.
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
A key to successfully establishing a new lawn is selecting the best-suited turfgrass species for the site. Kentucky bluegrass is the best-adapted turfgrass 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. The fine-leaf fescues perform best in shady locations. (The fine-leaf fescues include creeping red fescue, hard fescue, chewings fescue, and sheep fescue.) Perennial ryegrass is often used in seed mixes because it germinates and establishes quickly.
For sunny locations, select a seed mix containing 80 to 90 percent Kentucky bluegrass and 10 to 20 percent perennial ryegrass.
In lawns that contain sun and shade, select a mixture containing 50 to 60 percent Kentucky bluegrass, 30 to 40 percent fine-leaf fescue, and 10 percent perennial ryegrass.
Heavily shaded areas that receive less than 2 hours of direct sunlight should be seeded with 100% fine-leaf fescue. In most cases, heavily shaded areas should be planted with something other than turfgrass. Learn more in this article: Growing Grass in Shady Areas.
Buy a high-quality mix. Avoid grass seed mixtures containing a high percentage of annual ryegrass, weed seed, or inert material. The higher quality seed will be more expensive, but there will be fewer problems.
More information about selecting appropriate species of turfgrass can be found in this publication: Selecting a Grass Species for Iowa Lawns
Preparing the Site
The first step in planting a new lawn is establishing the rough grade. Remove construction debris, then fill in low spots and level off high areas. The ground should slope away from the foundation of the house, driveway, and sidewalks. The rough grading should be done well in advance of seeding to allow settling to occur.
At least 4 to 6 inches of good soil is needed to establish a lawn. If necessary, bring in additional topsoil or organic matter. Be sure the topsoil or organic matter is weed-free. Incorporate the additions such as topsoil, organic matter, and fertilizer into the top 6 inches of soil. Tilling is often the most effective method. Do not till the area when the soil is wet. The soil is too wet when a handful of soil formed into a ball retains its shape when pressed with the thumb. The soil is ready to till when the soil ball crumbles. Be sure not to over-till the soil, as this will destroy soil structure and is undesirable.
Rake the area to finish-grade just prior to seeding.
Fertilization
Fertilization is very important at seeding time. This is the only time you can incorporate the required soil amendments or fertilizer into the root zone.
To determine soil fertility, conduct a soil test. Apply the recommended fertilizer, then incorporate it into the soil. Where a soil test has not been made, apply 5 pounds of a 20-5-10 or similar analysis fertilizer per 1,000 square feet and till it into the soil.
The final step in soil preparation is hand raking the area. This is also the last opportunity to establish the final grade. Immediately prior to seeding, apply a starter fertilizer. A starter fertilizer is high in phosphorus.
Additional fertilizer may be needed 3 to 4 weeks after germination, when the grass is approximately 1 to 1.5 inches tall. More information on fertilization can be found in this publication: Lawn Fertilization.
Seeding
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.
Mulching and Watering
To promote seed germination, mulch the area with clean, weed-free straw. Mulching materials help to conserve soil moisture. They also prevent soil erosion and soil surface crusting. Do not apply too much mulch; it may smother the emerging seedlings. Approximately 50 percent of the soil should be visible through the straw. One bale per 1,000 square feet of area should be adequate. Erosion control mats or blankets (available at garden centers and home improvement stores) are excellent options when sowing seed on steep slopes and other erosion-prone areas.
After the ground has been mulched, water the area. Moisten the upper 1 inch of soil. Grass seedlings are very susceptible to desiccation, and the surface of a newly seeded lawn should not be allowed to dry. Water should be applied only as needed to keep the soil surface moist. Avoid overwatering and runoff.
After the initial watering, irrigate the area frequently and lightly. The objective is to keep the seedbed (upper inch of soil) continuously moist. Do not allow the seedbed to dry out during germination. This usually requires daily watering during this time. It may be necessary to water several times daily on windy, sunny days. When the grass seedlings are 2 inches tall, start watering less frequently but deeper.
When to Start Mowing
The new grass should be mowed when it is 3 inches tall. Make sure the mower blade is sharp. Mow at a height of 2 to 2.5 inches. Mowing at this time will promote the spreading and thickening of the grass. New lawn grasses should not be allowed to grow excessively long before the first mowing. If this occurs, it will be necessary to mow the grass in stages to prevent scalping and the removal of more than one-third of the tissue.
Broadleaf Weed Control
After you have completed the task of establishing your lawn, you will notice broadleaf weeds germinate along with the grass seedlings. Most broadleaf weeds can be easily controlled with a broad-spectrum, selective broadleaf herbicide like 2,4-D after the turf is established. It is safe to apply a herbicide after the lawn has been mowed at least 3-4 times. More information on broadleaf weed control can be found in this publication: Weed Control in Home Lawns.
More Information
- Establishing a Lawn from Seed (publication)
- Overseeding the Lawn
- Turfgrass Renovation (publication)