How to cut long grass — according to the experts

A red lawn mower cutting long grass
No two lawns are the same, so choose the right method and length for your property (Image credit: Getty)

You may be wondering how to cut long grass if you've neglected your lawn due to focusing on your build - or perhaps the grass has grown out of control during a lengthy period of heavy rainfall when it has been too wet to mow.

There's a few things you need to know before unleashing one of the best petrol lawnmowers on long grass, so that the grass is cut appropriately to make the most out of your garden design and keep your lawn looking smart and healthy.

Without preparation, you risk tearing the grass, which can damage your lawn as well as your lawn mower, which can get choked or overheat.

How to cut long grass 

David Hedges Gower, Chairman of The Lawn Association, says your approach should be guided by the state of the lawn.

 “Cutting foot-long grass down to 4in is very different from cutting from 4in down to 1in. There is more density in the lower few inches, which will lead to more clogging," he says.

It is better to go over the area a number of times, lowering the blades each time, instead of trying to do it all at once, he adds.

Meanwhile lawn expert Chris McIlroy of The Grass People says there’s no need to panic if you have left it a bit too long between each mow.

“If your grass blades have grown too long, we would recommend using a strimmer to cut them down to a more manageable length. After that, you can go ahead and carry out your normal mowing regime,” he says.

Guy Jenkins at Johnsons Lawn Seed adds: "To cut tall grass, raise your mower to the highest setting and work your way down. Carefully lift the lawn mower’s deck to lower it on your grass. Do small sections at a time to level your grass out. Rake up debris to make it easier.".

Can a lawn mower cut tall grass?

Even the best cordless lawn mowers are at risk of damage from an overgrown lawn. A rotary lawn mower should not mow extra-long thick grass due to the strain it will put on the mower. Average rotary mowers shouldn’t cut grass longer than 6in too often.

Chris said: “While your lawnmower may be able to cut longer grass, we don’t recommend trying it out and potentially damaging your lawnmower. Try using a strimmer first and then using your lawnmower when the height is more manageable.”

If the grass is very long, David recommends a flail mower, which are designed to tackle overgrown areas that may be full of other types of vegetation. 

These can be expensive to buy, this one on Amazon will set you back over £2,000, but they can be hired too. 

How short should I cut my grass?

David Hedges Gower, Chairman of The Lawn Association, says there is no such thing as a perfect height for grass as each lawn is so different. He says around 30mm is a good starting point for a fairly dense lawn, but this will require regular mowing practices. A height of around 50mm is better for a garden design that is not regularly mown but has good density and health.

“For a wild lawn, that can be taken over by weeds and moss and doesn’t promote grass as much as biodiversity, then either not at all or around the 75mm mark when you do mow,” he adds.

Chris says: “Generally, we all like a short and tidy lawn, however, we can all get a little too mower-friendly when we see how wonderful our lawn is looking. The truth is not all grass types will survive close mowing, and you can damage the grass by mowing it too short if it’s not used to it.”

Finer-leafed varieties such as fescues and bent grasses will tolerate close mowing for an ornamental appearance, which means mowing the grass to around 10-15mm. Meanwhile, a mowing height of 25-40mm is sufficient for a hard-wearing family lawn, a. During summer, your grass will need cut more frequently – ideally once or twice a week.

Chris adds: “This helps to keep it looking its best and become used to its weekly chop. Tell-tale signs that your grass has been cut too low are that it can turn yellow/brown at the tips. This may also be due to blunt blades. Your lawn may also begin to suffer from patches if you cut it too much in the summer months.”

Sam Webb

Sam is based in Coventry and has been a news reporter for nearly 20 years. His work has featured in the Mirror, The Sun, MailOnline, the Independent, and news outlets throughout the world.  As a copywriter, he has written for clients as diverse as Saint-Gobain, Michelin, Halfords Autocentre, Great British Heating, and Irwin Industrial Tools. During the pandemic, he converted a van into a mini-camper and is currently planning to convert his shed into an office and Star Wars shrine.