Grass seed spread on top of the soil will still attempt to grow, but you will get poor results compared to grass seed that has been covered with 1/4 inch of soil. Uncovered seed is prone to drying out, being eaten by birds, or carried away by water runoff. It’s also easier for uncovered grass seedlings to dry out and die. If you leave your grass seed uncovered, a much smaller percentage of grass seeds will sprout. To get more out of your grass seed and ensure a thick new grass lawn, cover the grass seed with a thin layer of soil or compost.
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Why You Should Never Leave Grass Seed Uncovered
Grass seed that is exposed to the elements is prey for scavenging birds or can be washed away from the frequent watering young seed requires. Not only that, but grass seed requires moisture first and foremost. Dry conditions are a death sentence for grass seedlings. Uncovered seeds can be dried out by the sun. This can lead to a situation where grass seeds can fail entirely in dry or sunny portions of your yard.
- Uncovered seed is prone to drying out, which kills seedlings.
- Much higher chance your grass seed is eaten by birds.
- The seedlings will struggle to root in hard, unprepared soil.
- Runoff from watering or rain can wash seeds away.
You will get fewer grass plants from your seed, meaning you’ll get less for your money.
Uncovered grass seed simply won’t sprout or survive in large numbers compared to covered grass seed. If left uncovered, only a small percentage of lucky grass seed will sprout, whereas most will die or never sprout at all. If you don’t cover your grass seed, you’re throwing money away, because the majority of the seed you paid for and worked so hard to spread won’t grow.
How Deep Does Grass Seed Need to be Buried?
1/4–1/2 inch (1/2–1 cm) of soil or compost is the perfect depth to bury grass seed. Any deeper and grass seedlings may struggle to punch through the soil and flourish. By burying grass seedlings, instead of just sprinkling them, you provide a perfect habitat for grass seed germination. Your watering efforts will keep soil moist, which incubates grass seed and encourages higher germination rates. That layer of soil also provides protection for your grass seed and provides a good place for grass seedlings to establish their initial roots.
- Cover grass seed with 0.25–0.5 inches of soil.
- Soil covering retains water and helps keep grass seed moist.
- Seeds will be protected from the sun that may dry them out as they attempt to sprout.
- Loose soil surrounding seeds makes for easy initial rooting.
- Seeds will be protected from hungry birds.
- The soil will help seed remain in place and resist runoff.
To properly cover grass seed, spread it over loose topsoil or compost and use a garden rake to lightly cover the seeds. It is okay if some seeds are visible as long as the majority are covered. To get even better results from your grass seeding, follow up with a lawn roller and a good starter fertilizer.
Will Grass Seed Germinate if Covered?
Covered grass seed will germinate at higher rates than uncovered grass seed as long as it is buried no more than 1/2 inch (1 cm) below the surface. If grass seed is buried deeper than 1/2 inch, the new shoot may not have enough energy to break the soil surface and reach sunlight.
- Grass seed experiences the most success when covered with 1/4–1/2 inch of topsoil or compost.
- Uncovered grass seed will struggle.
- Grass seed that is buried more than 1/2 inch deep may not be able to break the surface and will die.
- Lightly covered seed has the highest chance of success.
Keep in mind, the soil you use to cover your grass seed is primarily in place to keep the grass seed moist and protected. Because grasses send up very small seedlings, they do not tolerate being buried as deeply as leafy plants.
Should You Put Topsoil Down Before Grass Seed?
If you are seeding a bare lawn or a bare patch of soil, you do not need to add topsoil before spreading grass seed. Instead, you can prepare the soil by tilling and loosening it, making it perfect for grass seed. If you are overseeding an existing lawn with new seed, it is best to spread a thin layer of compost or topsoil before seeding, to provide a cover for the new seed.
- If you are seeding bare areas, no new topsoil is needed. Simply till and prepare the bare soil.
- If you are overseeding, spread compost or topsoil prior to seeding.
- Use only a thin layer of topsoil/compost when overseeding. Too much additional topsoil will smother existing grass.
When spreading topsoil on an existing lawn, make sure your grass is not covered. Spread the new topsoil a little bit at a time and use a garden rake to distribute it between the grass blades without burying them. This creates a habitat for new seeds without harming your existing lawn.
Will Grass Seed Grow if Not Covered with Dirt?
A small percentage of grass seed will sprout if it is spread and left uncovered. This method of seeding is very inefficient though. Rather than waste time and money spreading grass seed only to get a few sprouts, you will get much better results by spreading your grass seed and covering it with 1/4 inch (0.5 cm) of soil. This soil covering will serve as an incubator that keeps the grass seed moist and shields it from scavengers and rough weather. To get the most grass out of a bag of grass seed, cover it after you spread it on your lawn.