Is It Too Late to Plant Grass Seed? Here's How to Time It Right for the Best Growth

Whether you are overseeding a patchy lawn or starting a new lawn, when you scatter the grass seed matters. Time it right and the seeds will germinate, develop a strong root system, and create a dense lawn in a just a few weeks. Miss that optimal timeframe and you'll likely end up with less successful results.

Find out about the ideal lawn seeding window and follow these tips to save both time and money.

Know Your Grass Type

The kind of grass you are planting—cool-season or warm-season—determines the best seeding window. Warm-season grass, such as Bermudagrass, St. Augustinegrass, zoysiagrass, and centipedegrass, is prevalent in areas with mild winters where freezing temperatures and snow are rare. Cool-season grasses, on the other hand, are known for their ability to withstand long bouts of cold temperatures, ice, and snow. Kentucky bluegrass and fescue are common cool-season grasses.

Seed Warm-Season Grass in Spring

Rising soil and air temperature in late spring and early summer make this the ideal time to seed warm-season grass. Bermudagrass and zoysiagrass cultivars root quickly in warm conditions. Once germinated, the seedlings take off rapidly, expanding to form a dense lawn by the end of summer when warm-season grasses entering their winter dormancy.

Seed Cool-Season Grass in Fall

There are numerous benefits of seeding a cool-season lawn in late summer or early fall. First, warm soil temperatures combined with moderate air temperatures in early autumn create ideal grass seed germination conditions. Pair the ideal temperatures with regular rain that is often present in fall and the grass seed will germinate quickly. Once germinated, warm days and cool nights spur cool-season grass seedlings to put on rapid growth, establishing a strong root system along with dense top growth.

Unlike warm-season grasses, cool-season grass seed is commonly used for overseeding and starting a new lawn.

Fewer Weeds

An added benefit of late summer or fall seeding is the lack of germinating weed seeds. Lawn weeds thwart spring seeded lawns, popping up and overtaking young grass seedlings. This is rarely the case in fall as most weed seeds are dormant until spring. A fall-seeded lawn is usually firmly established by spring and can choke out spring weeds without the use of herbicides.

Don’t Wait Too Long

Earlier is better when it comes to seeding a lawn in late summer or fall. Grass seedlings are tender and need several weeks to gain vigor before frost and freezing temperatures blanket the lawn. A newly seeded lawn that isn’t winter-ready is especially susceptible to injury from freeze-thaw cycles in winter. Turf experts recommend seeding a cool-season lawn 6 to 8 weeks before the antipated first fall frost in your area.

Use Spring Planting as the Fallback

Spring takes second place when it comes to the best time to seed a cool-season lawn. Lingering cool soil and air temperatures in spring slow grass seed germination in spring. Regular spring rains spur germination, especially when the soil temperatures are on the rise. Unfortunately, spring weed seeds also tend to germinate quickly in these conditions, outpacing the slow-germinating grass seedlings. Herbicides are often required to control spring weeds in a newly seeded lawn.

Tips for Successful Fall Seeding 

Watch the calendar. Seed your lawn no later than 6 weeks before the anticipated first fall frost. Short days and cold temperatures slow grass growth. Give new seedlings ample time to mature before winter.

Eliminate weeds. Before seeding, clear the area of weeds. Many common lawn weeds are dormant in fall so this task should be simple. Do not apply a preemergent weed control; it will prevent the grass seed from germinating.

Ensure good soil contact. Firm seed to soil contact is essential for fast germination. Aerate an existing lawn before overseeding to encourage good seed-to-soil contact. Roll or rake a new lawn after seeding to ensure the grass seed is in contact with the soil.

Water. Rainfall in autumn can be spotty. Keep the seedbed moist until seeds germinate. When it doesn’t rain, provide young seedlings with at least 1 inch of water a week. Cool temperatures will limit soil moisture evaporation, reducing watering needs for fall-seeded lawns.

Mow before winter. Cut new turf at 2 to 3 inches tall going into winter. It might be tempting to leave grass standing tall with the assumption that the additional leaf tissue will insulate the plants—it doesn’t. Long grass is more susceptible to fungal diseases and rodent damage during winter.