How to Plant Grass Seed

Pick the right grass before you buy seed

Lawn grasses fall into two groups, and choosing the wrong one is the most common reason a new lawn fails.

Cool-season grasses (Kentucky bluegrass, tall fescue, perennial ryegrass and the fine fescues) grow most in spring and fall and suit the northern US and the transition zone, the band where cool- and warm-season grasses overlap. Tall fescue handles summer heat better than bluegrass and is the main lawn grass in Maryland and the most common one in California, according to Maryland Extension and UC IPM.

Warm-season grasses (bermudagrass, zoysiagrass, centipedegrass and St. Augustinegrass) grow in summer and turn brown after the first hard frost. They suit the South, the Southwest and other areas with long, hot summers.

Not every grass can be seeded. Clemson notes that several warm-season grasses produce no viable seed, and Virginia Tech that many of the best cultivars of bermudagrass, zoysiagrass and St. Augustinegrass must be planted as sod, plugs or sprigs. Clemson names centipedegrass, carpetgrass, common bermudagrass and Japanese lawngrass (Zoysia japonica) as the warm-season exceptions that can be grown from seed. Maryland Extension calls zoysia from seed challenging because the seed is costly, scarce and germinates unreliably.

Match the grass to your light. Maryland says lawns do best with six or more hours of direct sun after nearby trees leaf out, and no lawn grass thrives in deep shade. For partly shaded sites, Penn State suggests a mix of fine fescues, Kentucky bluegrass and a little perennial ryegrass, or tall fescue alone; for full shade, fine fescues or rough bluegrass.

Mixes and blends

Cool-season seed is usually sold as a mix of species or a blend of cultivars, and that is a good thing. Different species cover different conditions in the same yard, and Penn State recommends blending three or four Kentucky bluegrass cultivars because the species has so little genetic variation. Nebraska Extension suggests a blend of three or four bluegrass and/or turf-type tall fescue cultivars for fall seedings. UC IPM recommends that bluegrass mixes include at least 15 percent perennial ryegrass, which sprouts fast and holds the soil while the bluegrass fills in.

Warm-season grasses are the opposite: NC State and Virginia Tech advise planting a single variety rather than a blend.

Read the seed tag

By federal law every bag of lawn seed carries a label listing each species and cultivar, its purity, its germination percentage, the weed seed content and the date the seed was tested. It is the best guide to what you are paying for.

• Purity and germination. Clemson suggests buying seed with at least 90 percent purity and at least 85 percent germination.
• Named cultivars. “Variety not stated” (VNS) or “common” on the label usually means lower-quality seed (Penn State).
• Weed and crop seed. As low as possible. Nebraska looks for no noxious weeds and 0.5 percent weed seed or less.
• Test date. Germination drops as seed ages, so fresher is better.
• Certified (blue-tag) seed is the only real guarantee of cultivar purity, according to Penn State.

To compare bags fairly, work out the pure live seed (PLS): multiply percent purity by percent germination and divide by 100. Penn State’s example: 92 percent purity times 80 percent germination is 74 percent PLS. A cheaper bag with a low PLS often costs more per pound of seed that will actually grow.

When to sow

Cool-season seed: late summer to early fall. Warm soil makes the seed sprout fast, and the new grass gets two cool growing seasons, fall and the following spring, before summer stress (Penn State). Weeds are also less of a problem than in spring. Typical windows are mid-August to mid-September in Indiana and Nebraska, the last week of August to mid-September in northern Virginia, mid-August to mid-October in Maryland, and mid- to late September in South Carolina. Utah State says to allow four to six weeks before the expected first frost; Illinois says at least 45 days. Earlier is safer: Nebraska Extension notes that each week of delay adds two to four weeks to the time the grass needs to mature in fall. The dates for your zone above follow that rule.

Cool-season seed in spring: second best. Spring seedings face crabgrass and then summer heat before roots are deep. If you must seed in spring, do it as early as possible: mid-February to mid-March and no later than mid-April in Kentucky, March into early April in Maryland. Purdue also describes dormant seeding: sowing before the frost comes out of the ground, from about Thanksgiving through March in Indiana, so the seed waits in the soil and sprouts as soon as it warms.

Warm-season seed: late spring to early summer. Wait until the soil holds about 65 to 70°F, which NC State’s Pender County office ties to daytime highs around 80°F. Clemson’s target is May 1-14 for all of South Carolina, Tennessee plants from May 1 to June 30, K-State from mid-May through July, and Kentucky late May through June. Planting earlier invites seed rot in cold soil (Clemson); planting much later leaves too little summer for the grass to toughen up before winter (Virginia Tech).

Preparing the seedbed

1. Test the soil two to three months ahead (Clemson) so there is time to add lime or nutrients. Maryland puts the best pH for turf at 6.0 to 6.8.
2. Kill out weeds and old grass if you are starting over. Nebraska waits 10 to 14 days after a glyphosate application before seeding.
3. Loosen and improve the soil. Work any recommended lime and fertilizer into the top 4 to 6 inches. Maryland suggests tilling in 1 to 2 inches of compost where soil organic matter tests below 3 percent. Don’t till wet soil.
4. Add starter fertilizer. Penn State applies 0.5 to 1 pound of nitrogen per 1,000 square feet in a starter fertilizer and warns that more than 1.5 pounds can burn young grass.
5. Grade and firm. Rake out rocks and roots, smooth the surface, slope it gently away from buildings (Maryland), and firm it with a water-ballast roller (Clemson).

For overseeding a thin lawn rather than starting over, Nebraska mows the existing grass to about 2.5 to 3 inches and core-aerates in at least three passes to expose plenty of bare soil for the seed.

How to sow

Use a drop or rotary spreader rather than throwing by hand. Split the seed into two equal halves and sow one half walking north-south and the other walking east-west, with the spreader set to half the rate each time, to avoid stripes and skips.

How much to use per 1,000 square feet (Penn State and Maryland):

Grass	Seed per 1,000 sq ft
Tall fescue	6-8 lb
Kentucky bluegrass	2-3 lb
Fine fescues	4-6 lb
Perennial ryegrass	4-5 lb
Bermudagrass or zoysia	about 1 lb

More is not better. Penn State notes that very heavy seeding produces crowded seedlings that are more prone to disease, though slightly higher rates help when you sow past the ideal window.

Rake the seed lightly into the top 1/4 inch of soil (Clemson), then roll it with a light or empty roller for firm seed-to-soil contact. Grass seed needs light to sprout, so Maryland warns against burying it under more than about 1/2 inch of soil.

Finish with a thin mulch, especially on slopes. Penn State uses 80 to 100 pounds of weed-free straw per 1,000 square feet, about two to three bales. Maryland recommends a layer thin enough that you can still see some soil through it, and warns against hay, which carries weed seed, and mesh netting that can entangle wildlife.

Watering new grass seed

Water is the step that makes or breaks a seeding. Clemson calls it the most critical part of establishing a lawn from seed: if the soil surface dries out after the seed has swollen but before roots form, many seedlings die.

• First two to three weeks: water lightly two or three times a day, about 1/4 inch at a time, so the top inch of soil stays moist like a wrung-out sponge. On hot, windy days you may need more passes.
• After the grass is up: shift gradually to less frequent, longer waterings that wet the top 4 to 6 inches, working up to about 1 inch at a time (Maryland).
• Water in the morning or midday, not in the evening, so the leaves dry before night and disease has less chance (Maryland).

Watch for washouts. Heavy watering or a thunderstorm on bare soil moves seed into puddles and leaves bare streaks. Mulch helps, and Pender County’s office advises avoiding cold, waterlogged soil after sowing warm-season seed.

The first mowing and feeding

Start mowing when the seedlings are about one-third taller than the height you plan to keep. For tall fescue kept at 3 inches, that means mowing when it reaches 4 inches. Under good conditions that is typically four to six weeks after seeding (Maryland). Use a sharp blade; a dull one pulls seedlings out of the ground.

Clemson gives new seedlings a light feeding of about 1/2 pound of nitrogen per 1,000 square feet once they are 1½ to 2 inches tall. Hold off on most weed killers: Maryland and Purdue wait until a new lawn has been mowed at least three times before using broadleaf herbicides, and Maryland waits until four mowings before a crabgrass preventer. Many crabgrass preventers also stop grass seed from sprouting. Siduron and mesotrione are the exceptions Kentucky lists for use at seeding time.

Warm-winter areas and overseeding

Where winters are mild, permanent lawns are usually warm-season grasses planted in spring and summer. UC IPM sows common bermudagrass in spring or summer at about 1 pound per 1,000 square feet. To keep a dormant bermudagrass lawn green in winter, overseed it in fall with ryegrass: October to early November in north Florida, October to early December in central Florida, and October in Arizona’s low desert. In frost-free south Florida, lawns usually stay green without it.

Why grass seed fails

• Seed sown into cold soil or allowed to dry out after it swelled. Most germination failures come down to timing and water.
• Seed buried too deep. Keep cool-season seed in the top 1/4 inch and leave warm-season seed near the surface.
• Weeds. Spring seedings fight crabgrass. Maryland calls weed competition the most common cause of failed spring seedings; Purdue recommends seeding as early as possible to give grass a head start.
• Patchy stand. Usually too little seed, uneven spreading or low-quality seed. Overseed the gaps.
• Seedling disease. From overwatering, evening watering or sowing in hot weather.
• Fall seed that never came up. Maryland notes that seed that has not sprouted by winter dies, with the exception of Kentucky bluegrass, which can lie in the soil and come up in spring.

Seed or sod?

Seed costs less, offers more cultivar choice and is easy to blend for sun and shade, but it is slower and has a narrow planting window. Sod gives instant cover and roots in about two to three weeks. Maryland notes it can go down any time the ground is not frozen and daytime highs stay below about 90°F. For many warm-season grasses, sod, plugs or sprigs are the only way to get the best cultivars.