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.


Further Information