In this article I’m going to show you how to cut long grass.
We’ve all returned home from a week or two’s holiday to see the grass has grown taller than the house. Or you might have left a bit of height on the grass over winter and now it’s spring, it’s getting even longer.
Hack it all down at once and you’ll shock the grass. It’ll turn yellow or brown soon afterwards and it’ll take forever to recover.
So I’ll explain the process of mowing long grass to bring it down to your preferred height;
- Without wrecking you lawn, and
- While keeping it healthy a looking mint
Note:
When I refer to long grass, I’m talking about grass up to 4-5 inches high, not 2 feet tall.
If your grass is very long as a result of neglect (hey I’m not judging), you’ll need to use a strimmer. A lawn mower won’t cut it (pardon the pun!)
For lawns in this condition, you might as well hack it back to the bone and start again. Chances are, there will be other issues to deal with too.
[toc]
A Couple of Things to Bear in Mind When Cutting Long Grass With a Lawn Mower

Before we get into the actual ‘how-to’ there are a few things to bear in mind;
NEVER Cut More Than a Third Off the Grass’ Current Height
I say this so often I do my own head in but it’s important. Cutting the grass too short in one go will shock it and it’ll not be able to recover. Your lawn will turn brown, it’ll be a mess and you’ll wish you’d have been a little more patient.
Cut the Grass When it’s Dry
Cutting the grass when it’s wet is as bad as mowing it too short. The mower will tear the grass instead of cutting clean which bruises it. Moisture creeping into the wounded part of weakened grass can cause the onset of fungal disease like Fusarium Patch.
Mowing a wet lawn is also dangerous, especially if you have an electric mower. Not only that, but cutting long wet grass can overload your lawn mower’s motor, causing it to burn out. Plus, it’s a pain in the ass to clean afterwards.
If Possible, Use a 4-Wheeled Rotary Mower
I find they have the highest settings and the rotary action does a better job of cutting tall grass. Cylinder mowers are rubbish as many have front rollers. These tend to flatten the grass before it even reaches the blade. Even if you can get the grass into the blade, they often jam as the grass is too thick.
How to Cut Long Grass With a Mower, Step-by-Step

Let’s say you like your lawn best when it’s cut at 25mm. But you’ve returned from holiday and right now it’s currently 120mm tall.
How to mow the lawn to get if from 120mm to 25mm?
Little by little!
The First Cut:
If the grass is 120mm tall, you need to mow the lawn, reducing the height by no more than a third, which is 40mm.
So mow at 80mm (or as close as your mower will get to 80mm).
Then, the grass grow by 5mm before mowing again.
The Second Cut:
Now the grass is 85mm so mow again, reducing it by around a third or around 30mm. Depening on your mower it might need to mow to at 55mm or 60mm.
Again, let the grass grow 5mm.
The Third Cut:
At this point the grass will be around 60mm so mow again, sticking to the rule of thirds.
This will bring the grass height down to around 40mm.
Once again, let it grow by 5mm.
The Fourth Cut:
With the grass at 45mm cutting it by a third will reduce the height to around 30mm.
Let it grow by 5mm again.
The Final Cut
With the grass at 35mm high, you final cut will bring it down to 25mm
As you can see, it only took 4 cuts to get your grass down to your favourite height. So there’s no need to be in a rush to cut it off all at once.
Maintaining Your Lawn at Your Favourite Height
Once you’ve got your lawn down to the height you think looks best, you want to maintain it at that length.
The table below shows the height at which you need to cut the grass, based on how high you like your lawn.
Favourite Height (mm) | Cut At (mm) |
---|---|
10 | 15 |
15 | 22.5 |
20 | 30 |
25 | 37.5 |
30 | 45 |
35 | 52.5 |
40 | 60 |
To keep your grass healthy, you should mow at a sensible height, depending on the time of year. During spring and autumn, you can mow lower as growing conditions are perfect for grass recovery.
You’ll want to cut a little higher during summer to give the grass the ability to cope with the hotter, drier conditions. Same goes for winter. Keeping a bit of length will help it cope with cold, frosty weather.
The speed at which the grass is growing will dictate how often you should mow. Also bear in mind, the shorter you like your lawn, the more often you’ll need to mow.
For example, if you like your lawn at 20mm, you’ll need to mow before or when it gets to 30mm. But if you like a cut of 30mm you won’t need to mow until it reaches 45mm. That’s an extra 5mm of growth and time you’ve get between cuts.
If you’re not a keen gardener, you have a busy life, or you can’t be arsed to mow the grass so often, let it grow a little longer. You won’t have to mow as often then.