Mulch Over Grass Seed
Grass seed can be expensive. Whether you’re starting from scratch, overseeding some thin spots in your lawn, or regrowing a bare patch, you’ll want to give it the best opportunity to flourish.
I’ll address the question should you lay mulch over grass seed so that your time and money won’t go to waste.
And yes, you should lay mulch over grass seed. Here are some particulars.
Reasons to Mulch Over Grass Seed
The main benefit of laying mulch over grass seed is to protect the seed. Grass seed is very vulnerable to heat. It doesn’t take long for grass seed to dry out.
Mulch does a good job of keeping the seeds moist and regulating temperature. Mulch can also help to keep the grass seed in place. No one wants to lose all their seed to unexpected heavy rain.
The final reason is to offer some protection against birds and other small animals looking to chow down on your freshly seeded lawn.
What Kinds of Mulch to Use
- Straw
- Peat Moss (sphagnum moss)
- Compost
- Paper Mulch
- Sawdust
- Topsoil
| Mulch Type | Advantages | Disadvantages |
| Straw | Price, availability, moisture retention. | Residual pesticides, possible seeds. |
| Peat Moss | Price, moisture retention. | Nonrenewable, acidic. |
| Compost | Nutrient rich. | Time-consuming/ expensive, can smother seed. |
| Paper Mulch | Price, available in small quantity, easy to acquire. | Not as practical for larger areas. |
| Sawdust | Price, availability, moisture retention. | Must come from clean wood, removes nitrogen. |
| Top Soil | Price, availability. | Can smother seed, nutrient deficient. |
Straw Over Grass Seed
Straw is probably the most commonly used and readily available. It’s fairly cheap and very easy to find. Straw if bought in square bundles is easily transported, and only requires one person to move.
You can buy a larger rolled quantity but those are more densely packed. This makes it heavier, and also harder to distribute loosely.
You’ll want to spread the straw mulch over grass seed about a 1/4 inch thick making sure that it is pretty loose. This amount allows protection from the sun and moisture retention.
You won’t need to remove the straw once your grass seed takes off either, just mow right over it and it will even nourish your new lawn.
A potential downside to using straw mulch would be any potential residual pesticides remaining on the straw. A second but less concerning disadvantage would be the presence of seeds in the straw itself. The likelihood of this is far lower than the presence of seeds in hay.
Straw is also sold in the form of a mat that is easily rolled out over grass seed. This is optimal for hills and small slopes. Straw mat mulch will be a more expensive option, however.
Peat Moss (sphagnum moss) For Grass Seed
Peat moss is another cheap option and a fine alternative to straw that is often used to lay over grass seed. It isn’t nutrient-demanding, so it won’t rob your soil of everything it needs to nourish grass seed.
Peat moss can be loosely distributed over grass seed. It’s light enough not to smother your grass seed and does a great job of retaining moisture. Peat moss is often used in plant transplanting to help reduce environmental shock to the plants.
The disadvantages of peat moss are that peat moss is not renewable. Peat moss although incredibly abundant, takes hundreds of years to form and we’re using sphagnum faster than it’s able to replenish. A second disadvantage is that peat moss is acidic and that will transfer into the soil.
Most grass seed can tolerate slightly acidic soil, yet prefer neutral soil. There are types of grass seed that can tolerate acidity more than others such as Bermuda grass.
Paper Mulch For Grass Seed
Paper mulch is a fine option when you’re seeding small patches. It won’t add much as far as nutrients go but it’s cheap, often free, and you don’t have to commit to a large quantity. It breaks down easily, and you can mow right over it when your seed has taken root.
Paper mulch for weed suppression is an excellent addition when paired with other types of mulch. Adding a layer of newspaper or cardboard as a base layer does an amazing job at occluding the sun and restricting weed growth. If you want an even easier option try a paper mulch roll.
You can purchase bags of biodegradable paper mulch that also include fertilizer such as Green View. This is one of the best options for ensured success. These come in 4-15lb. bags and can cover between 200-1200 sq ft. This is the same stuff that they use to manage golf courses. That is the gold standard for lawns in my opinion.
According to Iowa State University Horticulture and Home Pest News newspapers are perfectly safe to use for garden applications and the ink used is in fact organic.
Compost For Grass Seed
Black gold, it’s good for everything right? Is it good for grass seed? Compost will certainly add nutrients to your soil however it can be a little too heavy for grass seed.
If you’re going to use compost for grass seed, use only a very thin layer or risk smothering your seed. Compost will certainly work but there are better options for seed cover and better ways to put your compost to work.
Sawdust Over Grass Seed
Using sawdust over grass seed is a very interesting and unique approach to germination. It’s organic (be careful to know what kind of wood was used to create the sawdust.) It’s literally cheaper than dirt. Sawdust holds moisture well and decomposes very quickly.
The problem with the quick decomposition is that it can sometimes rob your soil of nitrogen which is essential to the health of your grass seed.
This isn’t an issue if you’re leaving it to actually work itself into the soil. This will end up adding to your overall soil health.
Click here to learn more about sawdust as mulch.
Topsoil Over Grass Seed
Grass grows in soil so spreading topsoil over new grass seed makes perfect sense right? We can evaluate topsoil for grass seed just like we evaluated compost with a few notable differences.
Topsoil is pretty dense and can come in a few different varieties. It is quite heavy and really runs the risk of smothering the grass seed. The nutrient value of topsoil leaves a lot to be desired and with an abundance of alternative options, topsoil would be my last choice.
Will Grass Seed Grow if I Just Throw it on the Ground
Typically the answer is yes, however if you fail to add protection over grass seed you run the risk of wasting time and money.
Your grass seed may dry out in the sun, blow or wash away, or end up as a meal for any number of things. You may end up with a thin or patchy lawn, or grass that is weakly rooted.
There is an exception to this rule however in the process of overseeding.
What is Overseeding?
Overseeding is when you add grass seed to an existing lawn that is either patchy or beginning to thin. Ever cut a turn too hard while mowing the lawn and leave yourself with a bare spot? Overseeding is a good option here.
The reason that you may not need to mulch over grass seed when overseeding is that your soil is already pretty healthy and well-established. The existing grass will provide a little protection from the sun and check the box for moisture retention as well.
Best Mulch For Grass Seed
My choice for mulching over grass seed would have to be straw. Straw has the most benefits.
It’s inexpensive and easy to source. It does what you want it to do by protecting your grass seed, and has very minor downsides.
The easiest and most cost effective option would be a straw matt, especially for seeding areas on a slope.
Straw is the best mulch for new grass seed.
If you’re interested in other uses for straw in your garden then this is the article for you.
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