Overseeding is one of the best ways to promote a dense and vibrant turf. There are several ways you can prepare the yard to accept new grass seed, one being to cut the grass to better expose the soil surface. Cutting the grass at the time of planting also coordinates the period of rest your lawn will need as the new grass grows in.
While it won’t harm or disturb the seed to mow the day after sowing, you should incorporate mowing into preparation because germination will begin in the days following a seed application, during which time you should hold off on mowing for a few weeks. If you mow too soon after overseeding, it might interrupt the new growth’s successful establishment.
In This Article
Why Should I Overseed The Lawn?
Overseeding the yard allows you to strengthen the lawn without tilling up the existing grass. Your lawn won’t reseed itself because we cut it back before it can reach that size, and while some grasses fill in by stolons and rhizomes, others, particularly rye and fescue, grow in small bunches from seeds.
Even rhizome grasses like Bermuda and Zoysia will benefit from your seeding services to fill in gaps where they aren’t reaching. While grass wants to fill up as much space as it can, sometimes seeding the established lawn for more individual grass plants will be the best support for full coverage.
Preparing To Overseed
Mowing before sowing grass seed on your existing lawn is one of many steps you can take to support a supportive growing environment. Mowing a little lower than normal will expose the ground and allow you to reach the surface more easily with aerators, dethatching tools, or fertilizer before putting down the grass seed. All of these steps help the seed make contact with the soil while getting the right amount of nutrients, air, light, and water they need to germinate, establish roots, and sprout.
Should I Bag Or Mulch After Overseeding?
One advantage, however, of cutting grass after overseeding can come from leaving the grass clippings as a layer of mulch over the seeds. Mulch helps seeds germinate by providing a protective layer of organic material that allows light to penetrate through to the ground while keeping moisture in the topsoil surface. As the grass clippings decompose, the nutrients that lawns love, including nitrogen and carbon, are returned to the ground and delivered to the newly growing grass.
How Long Does It Take For Grass Seeds To Start Growing?
Grass seeds can sprout after about 48 hours of being put in the moist ground. They put out a small root first, then grow a green sprout that will emerge from the ground after a couple of weeks, the exact timing varying by grass type. All grasses have in common that from their time as seeds in the ground to maturity a few weeks later, they will need a lot of moisture: about 7 to 10 minutes twice a day, compared to once or twice a week for mature lawns.
When Should I Mow After Overseeding?
When you’re planning to overseed your lawn, there are a few ways it becomes challenging to mow once seeds are on the ground:
- Wet grass – When the lawn is getting extra water to feed the grass seeds, the lawn will be wetter than it usually is. Wet grass blades can get tangled in mower blades and tear them from the ground, so it’s always better to mow dry grass. The moist soil might also get muddy if you’re trying to do yard work during this time. When you’re planning to overseed, consider mowing before increasing the soil’s moisture levels.
- Growth disruption – After several days, grass seeds will begin to germinate. If any sprouts or young blades are damaged from being walked over or cut by a mower, it can disrupt their critical establishment period and those blades might not make it. Be sure to cut the existing grass before, or right after, overseeding to not disrupt new growth.
- Time constraint – Once the seed is on the ground, you have a small window to still cut the grass so that you won’t have to again for a couple of weeks while the grass grows in. If something comes up, and you’re unable to cut the grass in the day or two after overseeding, you may miss the window and end up a couple weeks later with a more overgrown lawn than you had hoped for as you wait for your new growth to mature.
Once the sprouts emerge, you should avoid mowing until it’s fully grown in, about an inch and a half taller than you will keep it normally. Depending on the grass type, this might be a couple of weeks or a couple of months. Rye and fescue are the fastest growing cool-season species, and Bermuda is the fastest among warm-season grasses. Grass types that grow quickly may only need a few weeks before they’re ready to cut, but Kentucky Bluegrass or Zoysia are slower growers that need double that time before you can mow.
At What Height Should I Start Cutting The Grass?
The perfect time to cut the grass once it has grown in will be different for each grass type. As the grass grows in, you should monitor its progress. Once the new growth has reached about an inch over the height you want to keep it at, you can begin cutting it on your normal schedule again. The type of grass, the height of your mature grass, and the growing conditions will all influence how soon you’ll be able to start cutting the grass again.
When the time comes, use sharp mower blades to be sure you get clean cuts and that the blades don’t rip or tear the grass. Clean cuts are easier for the lawn to heal, and it actually encourages healthy growth as the grass repairs and focuses on restoring what was lost.