Growing new grass is exciting (the kind of chore I long to do all winter). It's a good feeling when you finally start to see a green lawn pop up where there was once just dirt. But when it comes to mowing, jumping in too early can do more harm than good. Newly seeded lawns need time to settle in. If you cut too soon, you might pull it up or damage the young blades. The good news? It’s not complicated once you know what to look for.
Wait Until It Hits the Right Height
New delicate grass blades aren’t ready for a haircut right away. The grass needs to grow tall enough to build strong roots and get used to its environment. Cutting it too early can stress the grass plants and make it harder for the lawn to fill in. This is usually my problem... waiting.
Most grass types should grow to about 3 to 4 inches tall before getting out the lawn mower. A good rule of thumb is to wait at least 3 to 4 weeks after seeding—sometimes more, depending on the weather and seed mix. The grass roots may still be shallow at first, even if the blades look long enough.
The first mow should be gentle. Emphasis on gentle! Make sure your lawn mower has sharp blades, and follow the one-third rule, cutting only about a third of the grass height. That helps the plant stay healthy and keeps the roots growing. The first couple of times that I mow I like to use a reel mower, the blades are super sharp, it's lightweight, and I get some steps in.
Check the Ground First
The minimum height of grass growth isn’t the only thing that matters. You also need to pay attention to the soil. If it’s still soft or muddy, hold off. Mowing over wet or loose ground can leave ruts and tear up the grass you just planted.
You want the ground to feel firm under your feet. If you walk across the yard and your shoes sink or leave deep prints, it’s obviously not ready. Give it a few more days to dry out and settle. If you're still worried about the weight of your mower, consider using a reel mower until the seedlings are hardy.
Also, watch the weather. If it’s been raining a lot, that can delay your first mow. The soil will need extra time to dry, and the grass might be more fragile. Patience here really does pay off.
What About Sod?
Sod is a little different than growing a lawn from seed, but it still needs time to root before mowing. Most sod takes a couple of weeks to a month to start attaching to the soil. If you tug gently on it and it still lifts easily, it’s not ready for regular mowing.
Before you mow sod for the first time, check for:
- Grass height of at least 3 inches
- Sod that stays in place when tugged
- Firm soil beneath your feet
- Dry weather conditions—not wet or spongy
Once all of these are true, it’s time to mow. Just like with seeded grass, set your mowing height to cut no more than one-third of the blade height at a time. And keep those lawn mower blades sharp—dull blades can rip the grass, which slows growth and invites disease.
FAQ
Can I mow new grass if I used a starter fertilizer?
Yes, you can. Starter fertilizers encourage healthy growth and are made to help new grass seeds grow faster and stronger. They don’t affect when you should mow; the same rules still apply—wait until it’s tall enough and the ground is firm.
What happens if I mow new grass too early?
Cutting too soon can pull up seedlings or sod, damage the roots, and leave bald spots. Even if it doesn’t kill it outright, it can slow growth and make the lawn uneven. Waiting just a little longer can save you weeks of recovery.
