When can I cut new grass for the first time?
Cutting too early pulls seedlings out by the roots; leaving it too long lets the grass go leggy and thin. The height to judge by, and the one adjustment that matters more than timing.
- Difficulty
- beginner
- Time
- 12 min
- Read
- 4 min
Short answer
Wait until the new grass is roughly 7 to 8 cm tall, then take off no more than a third of its height with a sharp blade set high — around 5 cm. The blade being sharp matters more than the exact date, because a blunt one tugs seedlings straight out of soft ground rather than cutting them. Never mow when the ground or the grass is wet.
The instinct after sowing is to leave the new grass alone for as long as possible, and that is a mistake. Grass tillers — puts out side shoots and thickens up — in response to being cut, so a lawn that is never topped stays as a collection of single leggy seedlings rather than becoming a sward. The genuine risk of an early cut is mechanical: the seedling roots are shallow and the soil is soft, so anything that pulls rather than slices takes the plant with it. That risk is managed by height and by sharpness, not by waiting longer.
Step by step
- Judge by height, not by the calendar.Around 7 to 8 cm is the usual trigger. Autumn-sown grass may reach it in three to four weeks in warm soil, or take much longer in a cold late-autumn spell, so a date on the seed packet is a rough guide rather than an instruction.
- Check the roots before you start.Tug gently on a few seedlings in different places. If they hold firm, they are anchored well enough. If they lift out easily between your fingers, give it another week — that is exactly what a mower would do to them.
- Sharpen or replace the blade first.This is the step that decides the outcome. A blunt rotary blade tears rather than cuts and rips young grass out of soft ground. The catalogue's guide on lawnmower care covers sharpening properly.
- Set the mower as high as it will go.Aim to leave about 5 cm. You want to be removing the tips only. Setting it low for a tidy finish on a first cut is how people lose half a new lawn.
- Follow the one-third rule.Never remove more than a third of the leaf in one cut, on a new lawn or an established one. Taking more shocks the plant, which responds by putting energy into leaf regrowth instead of roots — the opposite of what a new lawn needs.
- Mow only when it is dry.Wet soil compacts under the mower and under your feet, and wet grass tears rather than cuts. On a new lawn this matters much more than usual because the surface is soft and the grass is not yet knitted together.
- Collect the clippings on the first two or three cuts.Clippings left on very short new grass mat down and smother seedlings. Once the lawn has thickened, leaving them is fine and returns nutrients.
- Lower the height gradually over the following cuts.Bring it down in stages over several cuts, never taking more than a third each time, until you reach your normal height. On an autumn sowing, keep it on the higher side through the winter — the catalogue covers how short to mow and when to stop for the year.
Common mistakes
- Scalping it to make it look tidy — New grass has almost no root reserve, so removing most of the leaf leaves it nothing to regrow from. This is the single most common way a promising new lawn is set back months.
- Waiting until it is very long and then cutting it short — It breaks the one-third rule badly and leaves pale stems and bare ground. If it has got long, bring it down over three or four cuts a week apart.
If it doesn't work
Seedlings pulled out in tufts during the cut
Cause: Blunt blade, or grass cut too early — Fix: Stop. Sharpen the blade and wait another week or two. Overseed the bare patches once the rest has established.
Mower wheels leaving ruts
Cause: Ground too wet — Fix: Wait for it to dry. Ruts in a new lawn set hard and stay for years, and compaction is one of the hardest lawn problems to reverse.
New grass looks thin and leggy after several weeks
Cause: Not cut yet — Fix: It needs the first cut. Grass thickens in response to mowing, and leaving it uncut is why some newly sown lawns never fill in.
Patches never came up at all
Cause: Washed away, eaten, or sown too thinly — Fix: Overseed the bare areas once the main lawn is established. The catalogue covers grass seed that has not come up and overseeding a patchy lawn.
Grass yellowing after the first cut
Cause: Normal short-term stress, or too much taken off — Fix: It usually recovers within a week or two. Water lightly if the weather is dry, and make the next cut higher.
Questions people ask
Can I cut new grass sown in autumn before winter?
Yes, and you should if it reaches the height — a light topping helps it thicken before the cold. What you should not do is cut it hard, or cut it once growth has effectively stopped, which the catalogue's guide on mowing in winter covers.
Should I walk on it before the first cut?
As little as possible. Light foot traffic to check the roots is fine; using it as a lawn is not, until it has been cut a few times and knitted together.
Does new turf follow the same rule?
Turf can usually be cut sooner because it arrives with an established root mat, but the same test applies — it should not lift when tugged, meaning it has rooted into the soil beneath rather than just sitting on it. The height and one-third rules are identical.