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Notebook · Guide 1 October 2026 · lawns

Mowing the lawn properly: height, frequency and the one-third rule

How high to cut, how often, and why you should never take more than a third off. Plus mowing in drought, the first cut of spring, and why a brown lawn isn't a dead one.

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Side-by-side cutaway of two lawns seen from the side: on the left grass cut very short with shallow, sparse roots; on the right grass left longer with a deep, dense root system reaching down into the soil.
1Short-cut grass (left) has shallow roots; longer grass (right) roots deeper.

Most lawn problems — moss, weeds, bare patches, a lawn that browns the moment the sun comes out — trace back to one habit: mowing too short. Cutting low looks neat for a day or two, but it weakens the grass and opens the door to everything you then buy products to fix. Get the height and the rhythm right and a lot of other lawn jobs shrink.

In pictures

  1. A single tall grass plant with a dashed line marking a cut that removes only the top third of its height.
    2Never cut off more than a third of the grass height at once.
  2. A lawn edge being cut with a half-moon edging iron, forming a neat narrow gutter between the grass and a flower border.
    3A half-moon edging iron gives the lawn a crisp edge.
  3. A lawn in high summer with a mown strip as a path running through an area of long, unmown grass full of small wildflowers such as clover and daisies.
    4A mown path through grass left long for wildflowers.

01At a glance

  • Ordinary garden lawns: up to about 40mm in spring and autumn; 13–25mm in summer.
  • Fine, ornamental lawns: 6–13mm all year — they need far more care.
  • How often: weekly or fortnightly in spring and autumn, about weekly in summer, less in drought. Usually not at all in winter.
  • The golden rule: never take off more than a third of the grass height in one cut.

02The one-third rule

If the grass is 6cm tall, cut no lower than 4cm. Take more and you shock the plant: it stops growing roots to regrow leaves, and the lawn thins out. If the grass has got away from you, bring it down gradually over two or three cuts a few days apart.

03The first cut of spring

Use the mower's highest setting. You're just tipping the grass, not shaping it — and long spring grass will choke the mower if you go straight in low. Lower the height gradually over the next few weeks.

04In summer and drought

  1. Raise the cutting height in dry weather. Longer grass shades the soil and roots deeper.
  2. Mow less often — and stop altogether if the grass stops growing.
  3. Leave the clippings on in very dry weather. They act as a thin mulch and help hold moisture.
  4. Don't water an established lawn, however brown it gets. The RHS is clear: the roots are still alive and the grass greens up once rain returns.

05Good habits every time

  • Keep blades sharp. A blunt blade tears the grass and leaves ragged, browning tips.
  • Don't mow wet or frosty grass. It damages the turf and compacts the soil.
  • Edge it. A crisp edge does more for how a lawn looks than any feed. Cut a small "gutter" with a half-moon edging iron or a spade, and trim the overhang with shears.

06Leave some long for wildlife

The RHS supports No Mow May: stop mowing in early May and let the lawn's own wildflowers bloom — ideally leaving it long until at least August for the biggest wildlife benefit. You don't have to do the whole lawn. A strip, a corner or a circle under a tree works, and mowing a neat path through it makes it look deliberate. Even simply mowing the rest once a fortnight rather than weekly helps.

07Mistakes to avoid

  • Scalping — cutting so low you see brown stems or soil.
  • Taking off more than a third after a holiday.
  • Mowing low in a dry spell.
Save your money
Don't water a brown lawn. It recovers on its own.
Don't feed or weedkill a drought-stressed lawn in autumn. The RHS says wait until spring.
A sharp blade beats a new mower. Get the old one sharpened before you replace it.

How we checked this

Every care and safety claim on this page is verified against horticultural and veterinary sources.

Sources: RHS — Lawn mowing · RHS — Lawn care for drought · RHS — May: lawns

Checked 1 October 2026. If our advice ever conflicts with the RHS, believe them and tell us.