How to Use a Lawn Mower Correctly (Without Wrecking Your Grass)

Using a mower correctly comes down to four things: cutting the grass dry, taking no more than a third of the blade height off in one pass, keeping the blade sharp, and overlapping your lines slightly so nothing gets missed. Get those right and the lawn recovers quickly instead of turning yellow and patchy. Everything else is detail worth knowing, but those four points do most of the work.

Check the lawn before you check the mower

Walk the lawn first. Stones, dog bones, hidden hose fittings and buried tent pegs are the usual culprits behind a bent blade or a cracked deck, and a mower will fire small objects out at real speed. Clear anything loose, then look at the grass itself. If it is wet with dew or rain, wait. Wet grass clumps, blocks the discharge chute, smears rather than cuts, and leaves the deck packed with a layer that dries like concrete.

Long grass after a holiday needs a different plan. Do not drop the mower to your usual height and force it through. Raise the deck to its highest setting, cut once, leave the lawn a few days, then lower a notch and cut again. Two or three staged passes over a week will get you back to normal height without scalping the grass down to bare stems.

Set the cutting height properly

Most UK domestic lawns are happiest somewhere around 25mm to 40mm through the growing season. Fine ornamental turf can go shorter, family lawns that take footballs and paddling pools do better on the longer side, and shaded areas should always be left longer because the grass needs more leaf to gather what little light it gets.

The rule that matters more than the exact number is the one third rule. Never remove more than a third of the grass blade in a single cut. Taking more strips away the leaf that feeds the plant, exposes the soil to sun and weeds, and turns the lawn a pale straw colour for a fortnight. If the lawn has run away from you, mow more often rather than lower.

Set the height with the mower switched off and, on a cordless machine, with the battery out. Adjust all four wheels or the single lever to the same setting. A mower with one wheel a notch out of line will cut a visible slope across the lawn.

Mowing pattern and technique

Start along the longest straight edge you have, usually a fence, path or border, and use it as your reference line. Work up and down in parallel strips, overlapping each pass by about a third of the deck width. That overlap is what stops the thin uncut ribbons that show up between lines, and it also feathers the stripe so the finish looks even.

Walk at a steady pace and let the mower do the cutting. Rushing gives the blade less time in each patch of grass, which means ragged, torn tips instead of a clean cut. If you hear the engine or motor drop in pitch, you are going too fast or cutting too low for the conditions, so ease off.

Change your direction each time you mow. Cutting the same way every week trains the grass to lean in one direction and compacts the soil in the same wheel tracks. Alternate between up and down, side to side, and the occasional diagonal to keep the sward standing upright.

For corners and awkward shapes, mow the perimeter first as a headland, then fill in the middle with straight passes. It saves reversing into borders and gives you a turning strip at each end.

Cordless, corded and petrol differences

• Cordless: keep a charged spare battery to hand and expect run time to drop sharply in long or damp grass. Raising the deck a notch will noticeably extend a charge.
• Corded: drape the cable over your shoulder and always mow away from the socket, working so the lead trails behind you and stays on the cut side. Use an RCD.
• Petrol: check the oil level before each use, never refuel a hot engine, and let it warm for a few seconds before you engage the drive.

Grass box, mulching or leaving clippings

Collecting clippings gives the tidiest finish and stops thatch building up, which is what most people want on a small lawn. Mulching returns nitrogen to the soil and works well if you mow often and only take a small amount off each time. What does not work is leaving thick clumps of long clippings sitting on the surface, because they smother the grass beneath and go slimy within days.

Empty the box before it is completely full. An overfull box stops the airflow that lifts the clippings into it in the first place, and you end up with a trail of debris behind the mower even though the box has room left.

What to do when you finish

Disconnect the power or remove the spark plug lead, then scrape the underside of the deck while the clippings are still soft. A plastic scraper or a stick works fine and a stiff brush finishes it. Grass left to bake on the deck restricts airflow, which directly reduces cut quality on the next mow.

Do not hose down a mower with the deck tipped, and never jet water into vents or around the motor housing. Wipe the top, clear the air intake, check the blade for nicks, and store the machine somewhere dry. If the blade is dull or dented, sharpen or replace it before the next cut rather than after you have already noticed the ragged brown tips.