How to Plant Grass Seed for a Lush Lawn, According to Horticulturists

It's easy to take grass for granted until it's time to establish a new lawn or reseed an existing one. Then, a simple thing like planting grass seed suddenly seems extremely complicated. How do you know when to plant the seed? How do you choose the right kind? And what about caring for it after it's planted? To ensure you have a lush lawn come spring, we asked horticulturists to share their tips for planting grass seed. Here's what they said.

Choosing Grass Seed for Your Lawn 

When choosing grass seed for your lawn, first consider the region you live in. "It's best to start with the question of whether you need a warm or cool season grass," says horticultural consultant Galen Gates. "A cool season grass is actively growing in spring; a warm season grass needs the warmth of summer to begin growing."

Cool-season grasses (bluegrass, fescue, and rye) are best suited to the northern part of the country. Warm-season grasses (Bermuda, centipede, St. Augustine, and zoysia) grow well in southern regions. There is also a central area stretching from Southern California to Virginia where a mix of both can be grown.

Once you know whether you need cool- or warm-season grass, you can get more granular. Consider the type of species you want to grow, whether you need a seed that thrives in sun or shade, and whether you want to grow one type of seed or a mix.

How to Read Grass Seed Labels

Grass seed labels contain lot of technical information. Knowing how to read the label ensures you get the best seed for your lawn.

Seed Percentages

Seed bag labels provide the percentage of each turf grass species in the mixture, says Aaron Steil, consumer horticulture extension specialist at Iowa State University Extension and Outreach. "Each of these grass species has different maintenance levels, wear tolerance, drought tolerance, and shade tolerance. It's important to match the species listed in the bag to priorities and site conditions."

Weed and Inert Matter Percentages

Some bags of grass seed also have percentages for things like weed seed, noxious weeds, and inert matter. "All of these percentages should be as low as possible," says Steil. "No seed source will be 100 percent free of weed seed, but the percentage should be 0.5 percent or less." 

Different states consider different species to be noxious weeds. "This number should be zero or nearly so as these weeds are difficult to control even with proper weed management techniques," Steil says. "The inert matter includes all of the material in the bag that won’t grow. High levels of inert matter means you are buying more material that won’t contribute any value to the lawn."

Label Date

Checking the date of the label can help you avoid sowing seeds that won't germinate. "As the seed ages, the germination percentages will go down," says Steil. "Avoid purchasing seed more than a year old."

Germination Rate

There should be a germination percentage on the label, indicating best results in ideal conditions. "This number will never be 100 percent, but it should be as high as possible," says Steil. "Often percentages in the 80s and 90 can be expected."

How to Plant Grass Seed

Plant cool-season grasses in later summer to early fall and warm-season grasses in late spring to early summer. Follow these expert-approved tips for sowing grass seed.

1. Prepare the Site

If you're establishing a new lawn from scratch, some soil prep can be helpful. "If starting a new lawn, this means removing construction debris, filling in low spots and making sure the ground slopes away from the home's foundation, driveway, and sidewalks," says Steil. "It is also important to establish a good seed bed to ensure good seed-to-soil contact and better germination." Tilling can be helpful to give the new seeds room to grow roots; Gates recommends tilling to a depth of 4 to 6 inches.

2. Rake the Soil

Use a steel landscape rake to smooth out the soil just prior to sowing. But don't try to pulverize every last clump of dirt. "You want small soil clods that melt once you start to apply water," says Gates.

3. Spread the Seeds

Spread grass seed evenly, avoiding thick clumps. Ideally, aim for spacing of about ½-inch or less between seeds. For large areas, use a mechanical spreader, or spread the seeds by hand. "Always rake after sowing so the seed drops just below the surface (otherwise, birds can dine happily)," says Gates.

4. Reseed Existing Areas

Without tilling, supplement existing areas of your lawn that look sparse with seed. Mow the area shorter than you normally would (1/2 to 2 inches) and remove any dead grass and weeds, says Stein. Sprinkle the seed over the existing grass and water well.

How to Care for Grass After Sowing Seeds

Keeping freshly sown grass seed moist is extremely important. "The objective is to keep the seedbed (upper inch of soil) continuously moist," says Steil. "Do not allow the seedbed to dry out during the germination period. Grass seedlings are very susceptible to desiccation, and the surface of a newly seeded lawn should not be allowed to dry."

To avoid overwatering and runoff, you should water just enough to keep the soil surface moist. "The first two weeks after seeding usually requires daily watering," he says. "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."