Benefits of Spreading Straw or Mulch Over Grass Seed

Grass seedlings poking up through straw mulch.
Grass seedlings poking up through a layer of straw mulch.

Why is new grass seed covered with straw? Can any kind of straw be used? -Jack

When seeding new lawns, it’s generally recommended that a thin layer of mulch be scattered on top. That mulch really only has one purpose – to hold in moisture to keep the seeds from drying out. It’s not as necessary when overseeding older lawns, because the existing grass helps hold in moisture.

As for what kind of mulch to use, there are several options:

  • Wheat, Barley, or Oat Straw: Yellow grain straw is the most popular choice. It’s inexpensive, readily available, relatively free of seeds, and as your new lawn grows, it’s pretty easily chopped up with the lawn mower. Don’t use hay, as it contains too many seeds.
  • Newly seeded patches
    Newly seeded lawn.
  • Compost: Finely screened regular or mushroom compost makes excellent mulch, because it also breaks down to deliver nutrients. Apply about a 1/4” layer to the ground.
  • Aged Pine Straw: Pine straw is a matter of some debate, because the needles contain chemicals (called terpenes) that suppress the growth of plants underneath. Ever notice that the grass is often thin under pine trees? However, those terpenes evaporate away quickly once the needles fall. So if you want to mulch your lawn with pine needles, use well-aged, brown needles that no longer have an aroma, rather than freshly-fallen pine straw from under trees.
  • Peat Moss: Well loosened peat moss can also be used as mulch over grass seed.
  • Sawdust: If you use sawdust, apply no more than 1/4” layer.
  • Manufactured Lawn Mulch: You can also try a commercial product. A biodegradable seed mat is especially helpful on slopes, because it holds itself together. Or, you can spring for a pelletized mulch-and-fertilizer combo such as Lesco Seed Starter 3 or Greenview Grass Seed Accelerator.

Lawn Mulching Tips

When mulching your newly seeded lawn:

  • Don’t use too thick a layer of mulch, which could choke out your new seedlings.
  • Scatter the mulch loosely; don’t layer it. If using straw, use your hands or a pitchfork to shake the straws loose.
  • Break up any clumps of mulch or straw.
  • When you look down at your mulched and seeded lawn, you should see about 50% mulch and 50% seed covered soil. If you apply it properly, you won’t have to remove the mulch later; it’ll just break down and disappear.

Julie

Further Information

13 COMMENTS

  1. I mistakenly aerated my yard ,then seeded and fertilized it with scotts weed and feed.I realize now the grass will probably not grow.Didn’t realize my mistake until after spreading hay.Is it possible to overseed with new seed in a few weeks on top of the hay,then water and get results

  2. I have a brand new home and would like to know what is better to used pine straw which I have now or mulch. I have a lawn guy and he stated that mulch look better and that’s what he has at his home.

  3. I planted a area of feild black dirt over a area I had a swimming pool. I planted grass seed and covered it with straw. The grass and many weeds are coming up. Do I need to remove the straw from this grass? I dont want to pull up the need grass!

  4. Don’t do it! The hay/straw you get at local suppliers is full of weeds and will infest your new grass! I speak from experience and having to de-thatch and rip up and re-topsoil and re-seed over 15,000 square feet. It’s a cheap way out that will bite you in the end. Just be diligent about watering seed 2x a day for 3-4 weeks and you don’t need to put junk on top of it. Save yourself my headache!

  5. over the last two years I have over seeded some parts of my lawn and newly seeded others about 4000 sq. ft. total I didn’t have a problem with any of it germinating or taking just loosen top 1 in. of soil apply granular starter fertilizer rake in lightly water good apply seed @ slightly more than recommended rate water in cover with 1/4″ to 1/2″ peat moss water in well and wait 10 -14 days new grass about 4 to 6 weeks later when grass reaches 4″ to 6″ tall mow it when dry follow up with 16-16-16 fertilizer watering regularly about 1/2′ to 1″ per week

  6. I was always curious about why people spread mulch over new grass. It makes sense though that new seeds need to keep moisture to be able to grow. How long is it recommended to keep the mulch on the grass? Thanks for the info!

  7. I’ve always used straw or a thin layer of top soil / peat mixture . Never use hay because of the weed seeds. Weed seeds germinate in the light, grass seed germinates in the dark. Spread it, roll it, lightly rake it then cover it.

  8. I have been working for about 10 years in greenery and mulch is necessary but the thickness is dependent on the climatic conditions, the slope of the area, and the size of the seed.

  9. So, I just re-seeded my back yard two weeks ago. I tilled my yard 6-8 inches (it was concrete) I then added a layer of “mesa magic” from my local green house, as of today I have one inch grass shoots growing under a bed of straw…

  10. this is my first time aerating grass seed in and covering it with straw the problem that I have is I don’t know if I put enough straw on the seed I heard you can use plastic to cover your see that you just have variegated but the thing is is I don’t have enough plastic what can I do I never done this before it just one night I had a dream that I wanted to show grass and I’m all about fun of my goals and dreams so can you tell me am I doing right or not doing right cuz I really don’t know what the hell’s going on

    • Hi, Clint,

      Gardening questions can be tricky since the rules can change based on the region. We would suggest ing your local Master Gardeners association.
      Master gardeners train on a range of topics so they can provide advice, at no charge, for people in their area.

      Thanks for your question, and good luck!

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