Grass seed germination requires moisture, warmth, and healthy soil.
To achieve ideal conditions for growth, cover the grass seeds with organic material.
Many homeowners use straw or grass clippings to cover the grass seedlings.
But can you cover grass seeds with compost?
Compost is excellent for covering grass seeds because it keeps moisture and heat in the soil. The compost also protects the seeds from harsh weather and wildlife. As compost breaks down, it adds vital nutrients to the soil for strong root development.
Keep reading to learn more about using compost with grass seed.
Is Compost Better Than Topsoil for Grass Seeds?
Compost and topsoil are very similar, but they have different uses.
Use topsoil to establish a new lawn when your existing soil quality is poor. It is also used to correct sloping or uneven areas in a lawn.
Topsoil comes from fields or building sites. It is more likely to contain weed seeds or chemicals from pesticides.
Compost is a soil amendment mixed with your current topsoil for extra nutrients.
The heat from composting kills weed seeds and reduces chemicals to trace amounts.
It is too expensive to create a new lawn with compost, so it is used as a top dressing.
Compost is the best choice for grass seeds if your lawn only needs general maintenance.
We recommend applying 3-4” inches of topsoil for lawns with low-quality soil. You must also fill uneven spots before planting grass seeds.
Add compost to the topsoil to give your lawn an extra nutrient boost and maintain soil moisture.
Putting a layer of topsoil on top of your seeds is bad.
The heavy topsoil will block sunlight, water, and oxygen, smothering grass seeds.
How To Use Compost When Overseeding
You must apply compost the right way when overseeding for the best results in grass growth.
A light layer of compost encourages seed growth by creating a warm, moist environment.
This ideal environment results in healthier grass and reduces your dependency on fertilizers.
Mow the Lawn
The first step in overseeding your lawn is to mow the grass shorter than normal.
For taller grass types like Tall Fescue and St. Augustine, the ideal height is 1.5-2” inches.
Mow shorter grass types like Bermuda and Zoysia to a height of around 1” inch.
Shorter grass makes it easier to aerate the soil and apply compost.
There should be visible ground between the grass blades after mowing. This ensures proper seed-to-soil contact.
Aerate the Soil
The next important step is to aerate your entire lawn.
Compacted soils make it challenging for grass roots to grow.
A thatch layer prevents nutrients and water from entering deep into the soil.
Aeration breaks up thatch and creates holes for the compost to enter the ground.
Core aerators are available for rent in many garden centers.
Compost is rich in nitrogen, usually in the form of uric acid.
Nitrogen is vital for strong root growth and for giving the grass its green color.
Uric acid evaporates in direct sunlight. The holes from core aeration allow the compost to reach below the soil surface and prevent nitrogen loss.
Once your lawn is mowed and aerated, it is time to add the compost.
Keep the layer of compost no more than a quarter-inch thick.
Applying too much compost will smother existing grass.
The amount of compost you need is roughly one cubic yard per 1,000’ square feet of soil.
You will likely notice a strong smell from your compost at first, but the odor will fade as it breaks down.
Spread the Grass Seed
Now you will spread the seed over the layer of compost.
Some recommend spreading grass seed before adding compost. This may cause the seeds to fall into the aeration holes.
If the grass seeds are too deep into the ground, they are less likely to sprout.
Follow the spread rates according to your bag of grass seed.
Use a broadcast spreader to apply an even layer of seeds.
Start with an east-west pattern. Go over your lawn again in a north-south pattern for full grass seed coverage.
Cover the Grass Seed
Rake the compost over your grass seeds with gentle strokes.
Maintain a seed depth of no more than a quarter-inch below the compost surface.
If the grass is buried deeper than this, it is more likely to go dormant or rot.
Once the seeds are covered with a thin layer of compost, use a lawn roller to ensure seed-to-soil contact.
Proper soil contact ensures more of your seeds sprout.
After rolling your lawn, water the seeds into the soil and compost.
Will Compost Burn Grass Seeds?
There is potential for compost to burn your grass seeds if it is not used in the correct way.
As compost begins to decompose, it releases a lot of heat.
Once the compost has settled after aging, its heat is less intense.
To avoid burning your grass seeds, only use aged compost.
If you are able to feel a significant amount of heat coming from your compost, it is not ready.
Visible chunks of organic material or ammonia smell mean your compost needs more time.
Other reasons your compost may burn your grass seeds include the following:
- High sodium content
- High carbon-to-nitrogen ratio
- Treatments with pesticides or herbicides
These issues rarely occur in compost made from leaf litter, grass clippings, or vegetable scraps.
Avoid using composts with manure content, as they are more likely to cause problems and burn your grass seeds.
Do You Need To Add Fertilizer With Compost?
Compost is a slow-release organic fertilizer that does not immediately provide nutrients to your grass seeds.
Instead, the compost releases nutrients into the soil as it breaks down over time.
Consider adding a starter fertilizer to provide your grass seeds with potassium and phosphorus. These nutrients are vital for your grass to form a healthy root system.
Always perform a soil test before adding fertilizer to your lawn to ensure you add the correct nutrients.
Fertilizers are available as liquids or granules.
It does not matter which type of fertilizer you choose. Be sure to follow the directions on the label to avoid overapplication.
Too much fertilizer will damage your grass seeds and keep them from sprouting.
What Is the Best Compost To Use With Grass Seeds?
The best compost for grass seeds contains a variety of organic matter.
Dried leaves, grass clippings, and chopped vegetables create a well-rounded compost.
These organic materials provide essential nutrients like nitrogen, phosphorus, and potassium.
A good compost will also contain vitamins and minerals like sulfur, iron, copper, and magnesium.
If you are unsure of the nutrients in your compost, you may have it tested.
Composts made from worm castings or animal manure are not recommended for use on grass seeds.
These types of composts contain high amounts of nitrogen and sodium, which will cause your grass seeds to burn.
Other items to avoid using in compost include:
- Meat and fish
- Treated wood
- Invasive weeds
- Diseased plants
- Charcoal ash
- Dog or cat waste
These materials will either cause your compost not to break down or introduce harmful diseases and bacteria to the mixture.
Where To Buy Compost
Compost is available in most hardware stores and garden centers.
Buying compost is convenient when you need a large amount for your lawn.
It is easy to make your own compost, but keep in mind the process takes several months.
This compost starter speeds up the decomposition process when added to your compost pile.
Adding two cups of compost starter per cubic yard of compost produces results in 2-3 weeks.
Placing worms in the compost also speeds up decomposition.
What To Do If You Add Too Much Compost To Grass Seeds
If you did not follow the recommended guidelines and added too much compost to your grass seeds, there will be visible signs, such as:
- Grass seed fails to germinate
- Existing grass turns yellow
- More pests and lawn diseases
- Muddy-looking lawn
While it may be too late to save your grass seeds, there are a few things to do to prevent the problem from worsening.
First, you must test your soil to find which nutrients are completely out of balance.
Once you receive your soil test results, you will be able to use the proper remedy for your issue.
Next, remove excess compost from your grass to prevent further damage.
The most common problem with using too much compost is a pH above seven.
There will also be increased levels of phosphorus in the soil.
Applying a sulfur solution to the soil or acidifying irrigation water will lower the pH.
Unfortunately, there is no way to lower the phosphorus in your soil.
To prevent adding more phosphorus, use a fertilizer containing only nitrogen.
Test your soil to confirm when phosphorus levels have returned to normal.
Final Thoughts on Using Compost With Grass Seed
Covering grass seed with compost is a great way to protect your new grass while supplying it with nutrients.
It is easy to find bags of compost in your local garden center or make your own with the help of a compost starter.
If you prefer to buy compost, read our article on 13 Best Bagged Compost High Quality And Readily Available to help you make the best choice.