1. Longer Germination Time
Grass seed can take up to 30 days to germinate, depending on the type. Perennial ryegrass, for example, will emerge in just 5 days in ideal growing conditions, while Kentucky bluegrass can take as long as 30 days to germinate.
When to Expect Grass Seed to Emerge
Here's a rundown of expected germination times for popular lawn grasses.
Bermudagrass: 10–30 days
Buffalograss: 14–30 days
Creeping bentgrass: 10–14 days
Kentucky bluegrass: 14–30 days
Perennial ryegrass: 5–10 days
Tall fescue: 7–12 days
Most lawn seed is a mix of two or three varieties of grass. The seed combination should be well-suited to the growing conditions on your lawn to germinate well.
2. Too Soon After Preemergent Application
Weed-and-feed lawn products and preemergent herbicides are very effective at preventing crabgrass and other pesky grass-like weeds. However, they also stop new grass seed from germinating. They remain effective up to eight weeks after application, so any grass seed planted within that window of time likely won't sprout.
If an area was treated with preemergent herbicide in spring, it will be necessary to delay seeding until fall—the next viable seeding window—when the chemical will no longer be active in the soil.
3. Low Temperatures
Soil and air temperature impact seed germination. Most species of grass seed germinate best when the air temperature is above 60°F. Tall fescue and perennial ryegrass germinate most readily when it's slightly warmer—temperatures above 70°F are ideal for these grasses. Wait to seed a lawn until the average daily air temperature is close to the ideal germination temperature for the grass seed you're using.
4. Inadequate Moisture
Grass seed will not start to grow in dry soil. Newly emerged seedlings are sensitive to moisture too. Seedlings will die quickly if the soil is allowed to dry out, even if for a few hours.
After seeding, moisten the upper 1 inch of soil. Then, water as needed to keep it moist but not wet. Be prepared to water multiple times a day during warm and windy conditions.
5. Heavy Rain or Strong Wind
Lightweight grass seed can easily be dislodged by moving water or high winds. Ensure seed-to-soil contact after planting by gently raking the seed into the top ¼-inch of soil. Mulch and erosion control blankets can be helpful too, especially on slopes. Spread clean, weed-free straw mulch over the seeded area; approximately 50% of the soil should be visible through the mulch.
6. Weed Competition
Vigorous weeds, such as crabgrass, can thwart the growth of grass seed and smother seedlings right after they emerge. Weeds steal water and nutrients from grass. If the seed manages to grow, nearby fast-growing weeds, will outpace the new seedlings, preventing light from reaching the young grass.
Take time to clear the seedbed of weeds before planting grass seed. Mow the new turf when it reaches 3 inches tall to both cut the grass and slow the growth of weeds. Hand weed as much as possible.
7. Fungal Issues
Lack of germination might be caused by a fungal disease. Warm, wet weather conditions activate certain fungi that can kill grass seed as it is germinating or right after seedlings emerge from the soil. Called damping-off disease, it causes young seedlings to quickly collapse and wither away, leaving behind patches of dead grass or bare soil.
The best defense is to plant grass seed in spring or fall when damping-off disease is less prevalent. Make sure to follow the recommended seeding rate on the seed package. Crowded seeds create a high-humidity environment near the soil surface, making seed more susceptible to damping-off.
8. Poor Seed-to-Soil Contact
Grass seed that falls on hard soil clods, stones, sticks, and other debris germinates slowly, if at all. Take time to prepare the seeding area by removing all debris and spreading a 4- to 6-inch-thick layer of topsoil, if necessary. After sowing seed, lightly rake the area to cover seed to a depth of 1/8 to ¼ of an inch. If you are seeding a large area, you can drag a small section of chain-link fence over the soil surface to make quick work of the project.
9. Old Seed
The seed itself might be the cause of poor germination. Several factors impact the quality of grass seed, with its age being the most obvious. As grass seed ages, its germination rate decreases. This is especially true if the stored seed was exposed to any moisture or temperature extremes.
Reputable seed companies list a "sell-by" date on the seed package. Check the date before seeding your lawn. Don't be tempted to buy seed out of bulk seed bins because you can't be sure how old it is.
