How Long to Wait Before Mowing New Grass? [Guide + FAQs]

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  • Post last modified:June 1, 2022

When it comes to growing grass, most people wait for too long before the first cut. Turfgrass specialists at Purdue University have some good advice on how to grow grass and when to cut it. So, when should you mow your new grass?

Since not every grass grows at the same speed, you should cut the grass once it grows above a certain height. That’s 1.5” for Kentucky bluegrass, perennial rye, and fine fescue, and 2” for tall fescue. This doesn’t hurt the lawn if you do it carefully, and it pushes the grass to fill in quickly.

Therefore, once the grass grows taller than those heights and you can cut at least 10% of the grass, you can safely mow it.

It doesn’t matter if you can only cut a small part of the grass, just make sure to use a light mower and be careful. A push mower is a good choice.

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When to Mow Overseeded Grass?

push mower cutting grass on lawn

A good piece of advice when overseeding is to scalp it down, plant the seeds, and then don’t mow for about 3 weeks. After that, you need to start thinking about getting your seedlings enough sunlight, or the current grass will take it. Just be careful when making turns not to damage the seedlings.

Cutting new grass after aeration and overseeding needs to be done at the right time – cut it too early and you scalp it, but wait too long and the root growth is diminished. If you don’t do it right, you could lose all entire work. This is why lawn maintenance skills are useful.

So, a general rule for mowing an overseeded grass is to wait until your existing grass starts overshadowing the new grass. As you mow it’s a good idea to bag it. Wait one week, then mow it again. After that, you can return to your regular mowing schedule, or whatever suits your new grass.

When to Mow Your Newly Seeded Lawn?

According to Turfgrass Extension specialists at Purdue University, the newly seeded lawns should be mowed early and often. For the best results, Kentucky bluegrass, perennial rye, and fine fescue should be mowed once they grow above 1.5 inches, and tall fescue when they pass 2 inches in height. 

After the first 3 to 4 mowings, you should increase the height of the mower to 2.0-3.5 inches for Kentucky bluegrass, perennial rye, and fine fescue, and 2.5-4.0 inches for tall fescue. If you’re looking to mow in rain, make sure it was only light rain, and that your lawn is kept clean.

Most people wait for too long, but it doesn’t matter if in your first mowing you only cut 10-20% of the grass. This is fine for the first time, and doing this will push the grass to fill in quickly.

The time to mow usually happens about 1-2 weeks after germination, but it’s best to mow based on the height, rather than on time. Different mixes take different times to germinate or grow, plus the time will depend on the soil, the sunlight, and a few other factors.

There’s no specific time to wait before mowing for the first time, so just do it when it grows above those heights. Choose a lighter mower, such as a push mower because it helps avoid creating divots in the soft turf.

Since most push mowers can’t cut above 2 inches, you might opt for Earthwise 1715-16EW because it can go up to 2.5 inches. It’s also very light, which is good so you don’t damage your new lawn and is rated highly as a quality product.

What Happens if You Mow New Grass Too Soon?

Mowing the grass too soon or carelessly can damage the root system and pull the seedlings out of the ground. New seeds need time to germinate and to put down roots, so you’ll need to give them at least a few weeks to germinate before you can plan to mow.

If you know the right height to mow your new grass, then you can’t mow it too soon. As long as you can trim at least 10% of the new grass, you can mow your grass. Check above for the right hights for different types of grass.

Does Cutting New Grass Help It Grow?

Cutting new grass helps the grass spread and fill in quickly. Low regular mowing will encourage lateral growth, and trimming the top sends the energy to the root growth which helps it grow. This also allows more sun to penetrate and encourage growth, just make sure ot use sharp blades.

And remember never to take off more than ⅓ of the grass blades, as it can cause damage to your grass. Cutting no more than one third is just enough to keep your lawn healthy and not too much to stunt the growth.

To avoid this, try not to get into your habit of leaving the grass to grow too long and then cutting it too short. Doing this often will damage your lawn. Cutting long grass short too many times will stunt growth and open up the turf for the weeds to thrive.

Should You Bag or Mulch When Mowing New Grass?

Your first few mows should generally be bagged, as this will give it more room to fill in. After the first few mowings, you can leave the clippings. However, mulching is also possible, as long as you’re not leaving clumps of grass.

For mulching, you need a proper mulching blade for your mower. You can get a mulching blade for about $20-30 on Amazon. These mulching blades are specially designed for mulching and produce very small clippings that can be easily decomposed.

french bulldog sitting in a grass lawn

Mulching is a good option for those who want the nutrients returned to the lawn, which means less fertilizer used on your lawn, without contributing to thatch buildup, while increasing microbial activity.

Just make sure not to leave any clumps on the grass.  In case of clumps, just go over the lawn quickly with a blower to break up any clumps left.

Should You Mow Before Overseeding?

Mowing before overseeding is generally recommended because it allows for new grass to get some sun, so it’s best to cut it as low as possible. A height of about 1.5 to 2 inches is good so that the existing grass isn’t too tall that it blocks the sun from the new seedlings. Make sure to bag the clippings.

Since you’ll probably be seeding new grass in spring or fall, there shouldn’t be any problems with drought stressing the grass, which is why you can go so low as to scalp it.

How Often Can You Cut New Grass?

New grass should be cut often, and as soon as it gets above 1.5 inches for Kentucky bluegrass, perennial rye, and fine fescue, and above 2 inches for tall fescue. Do this 3 or 4 times, after which you can increase the height of your mower. You should cut it as often as it needs to, but usually every 5 to 7 days.

There’s no time when you need to cut it, so the best thing is to mow when it’s ready to mow, or when it gets above those mentioned heights. Be sure not to mow with something heavy, and try to be careful making turns. The new turf doesn’t have deep roots so the mower can do a lot of damage if not careful.

FAQs:

How long does it take for grass seed to grow?

Takes about 2-4 weeks for the grass to germinate, and another 4 to establish. Seed germination can happen at different speeds depending on the mix you used. Perennial ryegrass is usually the fastest growing, followed by fine-leaf fescues and Kentucky Bluegrass.

What to do if grass seed doesn’t grow?

Most lawns in bad shape have unique issues, and there may be different answers depending on the lawn. Usually, if you’ve been regularly watering your newly seeded grass, but it doesn’t grow then it may be time to fertilize it. Newly seeded grass should be fertilized about 6 weeks after seeding, but it can happen sooner if needed.

There may also be too much nitrogen in some areas on your lawn. To find this out, you need to test the soil. If too much nitrogen is encountered, you should water these areas heavily for a few weeks to wash out some of that nitrogen, then try seeding again.

Additionally, you could just cut the sod that isn’t working out, and replace the area with a fresh new sod, ready for the new grass. Find out the best sod cutters you can get, and whether you should buy or rent.

Should I cut new grass before winter?

Typically, it’s considered best to trim your grass to 1.5 to 2 inches before the snow, once you can confirm that the grass has stopped top growth and right before prolonged freezing temperatures. You should never cut frozen grass because it damages the plant.

Keep in mind that you should have seeded at least 3-4 weeks before the typical first frost in your area. This way you have time to mow, and the grass had time to establish itself.

How long after planting grass seed can you walk on it?

Generally, light walking on the newly seeded grass is OK, whether overseed or new seed. If it’s an overseed then you should be fine walking on grass the next day. If it’s a new seed, then light foot traffic is fine, but consistent foot traffic is not recommended for at least a month.

As far as pets and critters go, keeping the animals off the lawn for 1 to 2 months is a good idea, 4 weeks at least. You may be fine with just walking the dog on a leash in a week or two, but otherwise, it’s risky to just let the dog run around before the grass is established.

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  • Hi, I'm the founder of HowMonk.com! Having been in finance and tech for 10+ years, I was surprised at how hard it can be to find answers to common questions in finance, tech and business in general. Because of this, I decided to create this website to help others!