Grass seed should be covered with 1/8–1/4 of an inch (3–6 mm) of soil for best results. This ensures the grass seed is surrounded by moist soil that encourages seed germination and protects the seed from birds and the elements. While 1/8–1/4 inch depth encourages the highest germination rate, most grass seeds will still sprout if buried as deep as 1/2 inch (1 cm). At depths greater than 1/2 inch, grass seeds may struggle, fail, or not sprout at all.
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Why Does Grass Seed Need to Be Covered?
Grass seed benefits from being covered by 1/4 inch of soil because the soil provides a moist habitat that triggers grass seed germination. No matter what type of grass seed you are planting, it needs moist conditions to germinate and survive its first few days of life. Uncovered grass seeds will dry out quickly in the sun. They will fail to sprout, or the grass seedlings will die during a warm afternoon.
- Soil retains moisture, which encourages grass seeds to sprout and survive long enough to send out their first roots.
- A layer of fresh, loose soil around the seedling creates a perfect habitat for new grass roots.
- Grass seeds covered in soil are protected from water runoff, temperature changes, and scavenging birds.
By laying fresh topsoil on your lawn and covering your grass seeds with it, you also provide a layer of soil where grass plants can send their initial roots. This can be much easier for seedlings than trying to root in hard, unprepared ground on top of soil. Additionally, grass seeds that are protected from the elements are insulated from deadly cold snaps, prevented from being carried away by water runoff, and hidden from birds that will eat the seeds.
What Happens if You Don’t Cover Grass Seed?
Grass seed that is left uncovered and just sprinkled on the ground will germinate at a very low rate. In fact, some varieties of warm-season grasses won’t sprout at all if the seeds are not covered. Uncovered grass seed will give you very little return for the money spent on seed.
- Uncovered grass seed will sprout at a low percentage—or not sprout at all.
- Grass seed without a soil covering is prone to drying out and struggles to take root.
- Uncovered grass seed can be damaged by changing soil temperatures, eaten by birds, or washed away by heavy rain or watering.
Grass seedlings are extremely vulnerable. A sunny day can dry out uncovered seedlings in a matter of hours, killing them. If they’re not insulated by soil, an out-of-season frost can kill off seedlings as they try to sprout. Birds will also eat grass seed that is exposed on the soil’s surface, greatly reducing the amount of grass that grows to form a green lawn.
How to Cover Your Grass Seed
The best way to complete a lawn seeding project is by spreading topsoil or compost on your lawn, spreading seed, and then raking the soil over the seeds to cover them. To accomplish this, you can add additional soil as necessary, until grass seed is covered to a depth of 1/8–1/4 inch. Special care should be taken depending on whether you are seeding bare soil or overseeding a lawn where grass is already growing.
Covering Grass Seed on Bare Ground
To cover grass seed on bare ground, first prepare the bare soil by loosening the top 6 inches (15 cm) with a rake, tiller, or shovel. Then, spread a lawn starter fertilizer on the soil. Once this is done, you can spread your grass seed evenly over the area at the rate recommended on the bag. Finally, rake the soil to cover the grass seeds to a depth of 1/8–1/4 inch (3–6 mm) and water the soil.
- Prepare soil for seeding by breaking up the top 6 inches (15 cm) with a tiller or shovel.
- Spread this lawn starter fertilizer over the bare soil at bag rates.
- Spread grass seed on the soil.
- If you are seeding a small area, it’s okay to seed by hand. If you are seeding an entire yard, use a broadcast spreader for even seed coverage. Make sure you know the number of square feet in your yard, so you can follow bag seeding rates.
- Rake loosened and prepared soil to cover seeds at a depth of 1/8–1/4 inch (3–6 mm).
- Water the soil for 10–15 minutes immediately after seeding.
This simple process will set your grass seed up for success both in the short term and the long term. Your seed will be protected, and moist, which causes seed germination. The loose, well-fertilized soil will give your grass a healthy start, making sure every grass seedling has a chance to grow into a mature grass plant.
Covering Grass Seed when Overseeding
Overseeding an existing lawn with new grass seed is a tough job. The grass that is already present can shade out new seedlings if the proper steps aren’t taken. For the best results, dethatch your lawn first. Then, use a core aerator to loosen the soil. Spread lawn starter fertilizer, followed by a 1/4 inch layer of compost. Then, spread the grass seeds, cover your seeds by raking the compost over them, and water your lawn.
- Dethatch your lawn if the thatch layer is more than 1/2 inch (1 cm) thick.
- Aerate your lawn using a core aerator.
- Apply lawn starter fertilizer in the area that will be overseeded.
- Spread 1/4 inch of compost over the lawn. Rake it to fill aeration holes and ensure it does not smother existing grass.
- Spread grass seed. Use additional seed if desired, since it is more difficult for seeds to sprout in an established lawn.
- Use a rake to cover the grass seed with 1/8–1/4 inch (3–6 mm) of compost.
- Water for 10–15 minutes immediately after the seed is covered.
Some types of grass respond better to overseeding than others. Cool-season grasses are good candidates for overseeding because most varieties do well growing in established lawns. Warm-season grasses may struggle when overseeding. By preparing your soil properly, you get the best results from overseeding with all grass types.
Can You Plant Grass Seed Too Deep?
Grass seed planted deeper than 1/2 inch (1 cm) likely will not sprout. To get the most out of grass seed products, plant grass seeds no deeper than 1/4 inch (6 mm). Although some cool-season grasses can experience germination when planted as deep as 1 inch, this is very rare, and only a small percentage of planted seeds will grow. When planting grass seeds, a thin covering of soil will give you the best result.
Does Grass Grow in 2 Inches of Soil?
Grass buried 2 inches below the ground will not sprout and grow. The seeds will either remain dormant or rot underground. Do not bury your grass seeds deeper than 1/4 inch. Also, plant grass where there is adequate soil depth for grass root development. Do not plant seed in a thin layer of soil over concrete or rock. Grass roots grow at least 6 inches deep. Shallow soil will cause grass to struggle and die.
How Deep Should Grass Seed be Planted?
Plant your grass seeds at a depth of 1/8–1/4 inches (3–6 mm). This is the perfect depth to surround the seeds with moist soil without smothering the grass seedlings or causing your seeds not to sprout. To cover the seeds, spread compost or topsoil, followed by spreading your grass seed. Then, use a garden rake to lightly cover the seeds with a thin layer of soil.