When to Plant Grass Seed

Cool-season grass: late summer to early fall

Tall fescue, Kentucky bluegrass, perennial ryegrass and the fine fescues grow best in cool weather, and the best time to sow them is when the soil is still warm but the air is cooling. Penn State explains why: warm late-summer soil makes the seed sprout fast, and a late-summer seeding gets two cool growing seasons, fall and the next spring, to root before its first summer. Penn State adds that weeds are less of a problem than in spring, because cool fall weather and frost check them.

The deadline is set by the first frost. Utah State says to allow four to six weeks before the expected first frost, and Illinois prefers at least 45 days. Aim for the early end. Nebraska Extension notes that each week of delay adds two to four weeks to the time the grass needs to mature in fall, and advises seeding tall fescue no later than mid-September in Nebraska because its seedlings are slow to harden for winter. The dates for your zone above count back from your local average first frost.

Typical windows from extension services:

• Upper Midwest and Plains: mid-August to mid-September (Purdue for Indiana; Nebraska Extension)
• Kentucky: mid-August to late September for tall fescue
• Northern Virginia and lower-elevation western Virginia: the last week of August to mid-September, possibly as late as mid-October (Virginia Tech)
• Maryland: mid-August to mid-October
• South Carolina: mid- to late September (Clemson)
• Southern and southeastern Virginia: September 15 to October 15

Maryland’s guide puts the best soil temperature for grass seed germination at 50 to 70°F, measured about an inch deep.

Cool-season grass in spring: second best

Spring seeding works, but with more risk. Seedlings must compete with crabgrass, and their roots are still shallow when summer heat arrives. Maryland calls weed competition the most common cause of failed spring seedings.

If you need to seed in spring, go as early as you can. Kentucky suggests mid-February to mid-March and no later than mid-April, using forsythia bloom as a cue. Maryland gives March into early April, and Virginia Tech mid- to late March for northern Virginia. Seed sprouts once the soil passes about 55°F (Purdue). Plan on watering through the first summer, and use only a crabgrass preventer labeled safe at seeding, such as siduron or mesotrione (Kentucky).

Dormant seeding is a third option in cold climates. Purdue sows cool-season seed while the ground is still frozen, from about Thanksgiving to March in Indiana. Freezing and thawing work the seed into soil cracks, and it sprouts as soon as the soil warms in April or May.

Warm-season grass: late spring to early summer

Bermudagrass, zoysiagrass and centipedegrass seed needs warm soil, about 65 to 70°F. NC State’s Pender County office says that usually comes with daytime highs around 80°F. In frost terms that is roughly five to ten weeks after the average last spring frost, once the danger of frost has passed:

• South Carolina: May 1-14 statewide (Clemson)
• Tennessee: May 1 to June 30 (University of Tennessee)
• Kansas: mid-May through July for bermudagrass (K-State)
• Virginia: May and June plantings survive their first winter best (Virginia Tech)
• Maryland: mid-May into June

Clemson warns that seeding too early, into cool soil, slows growth and raises the risk of seed rot. Seeding too late is the bigger danger in the upper South: the grass has too little warm weather to build roots and runners before cold arrives. Virginia Tech advises against late-summer plantings, and UF/IFAS warns that seedlings planted too late in the fall in north Florida may be killed by winter cold. In frost-free south Florida, UF/IFAS says lawns can be planted year-round.

Warm-season sod, plugs and sprigs follow a similar calendar: late spring to early summer, while the grass is actively growing.

Sod is less fussy

If you miss the seeding window, sod is an option. Maryland notes that cool-season sod can go down any time the ground is not frozen and daytime highs stay below about 90°F, and Utah State lays sod almost year-round wherever water is available.