How short should I cut my lawn, and how often?

Grass feeds itself from its leaves and roots to roughly the depth its leaves are tall. Cutting short repeatedly gives a shallow-rooted lawn that browns in the first dry fortnight and lets moss and weeds in, which is why the same lawn fails every summer.

What you'll need

• A mower with adjustable height
• Sharp blades

Step by step

1. Apply the one-third rule.Whatever the current height, take off no more than a third. Long grass therefore needs two or three cuts a few days apart to get back down, not one scalping.
2. Set 25 to 40mm for an ordinary lawn.Lower than 25mm only suits fine ornamental turf that is fed, watered and cut twice a week. A family lawn cut at 20mm will thin out.
3. Raise the height in hot dry weather.Going up to 40 to 50mm shades the soil, keeps roots cooler and slows moisture loss. It is the cheapest drought protection a lawn has.
4. Raise it in shade too.Grass under trees or beside a north wall has less light to work with, so leave it more leaf. 45mm or more is realistic there.
5. Cut more often rather than shorter.Weekly in April to June and again in September, fortnightly through midsummer. Frequency is what makes a lawn dense, not height.
6. Start high in spring and finish high in autumn.The first cut of the year should just top the grass. The last cut before winter should leave it a little longer, since short grass going into a wet winter invites disease.
7. Keep the blade sharp.A blunt blade tears rather than cuts, leaving a whitish frayed tip that browns off and lets disease in. Sharpen once or twice a season.
8. Vary the direction.Mowing the same way every week presses the grass over and creates ruts. Alternate at right angles or diagonally.
9. Leave the clippings when you can.Short clippings from frequent cutting fall between the blades and return nitrogen to the lawn. Only box them when the grass is long, wet or full of weed seed.

Tips

• The rule is a third off, not a target height. A long lawn needs several cuts, days apart.
• Raising the height in a dry spell does more for a lawn than watering it.
• A blunt blade shows as a whitish haze across the lawn a day after cutting.

Common mistakes

• Cutting short so it can be left longer between cuts — It is exactly backwards. Scalping weakens the grass, so it thins, moss and weeds fill the gaps, and the lawn needs more work not less.
• Mowing wet grass low — Wet grass compresses under the roller and cuts unevenly, and the clippings clump and smother what is underneath.

If it doesn't work

Questions people ask