Independent comparisons. We may earn from shop links. More info

How to mow a lawn

Updated: October 2026

The grass has jumped, the socket is in the kitchen, and you want the job done before the rain. How to mow a lawn in Britain is mostly three limits: dry grass, no more than about one-third off in a pass, and, if the mower has a lead, that lead stays behind you on an RCD. The [lawn mower comparison](/hub/lawn-and-garden-equipment/lawn-mower) matters only when a stated height range cannot make the cut the RHS describes. This page does not rank the eleven machines. Peter F. used RHS guidance and Electrical Safety First’s garden advice, checked against the saved listings on 22 October 2026. A qualifying Amazon purchase can earn us a commission at no extra cost to you.

The grass has jumped, the socket is in the kitchen, and you want the job done before the rain.

Our top picks

Flymo Flymo Speedi-Mo 360C

Best overall

Flymo Flymo Speedi-Mo 360C
9.2/10about £110
View offer
swift swift EB122C 22 cm

Alternative

swift swift EB122C 22 cm
9.0/10about £134.99
View offer
Flymo Flymo Hover Vac 250

Rank 3

Flymo Flymo Hover Vac 250
8.2/10about £75
View offer
On this page
  1. 1.When to mow in Britain
  2. 2.How much to take off
  3. 3.The first cut and long grass
  4. 4.The lead, the RCD and the blade

When to mow in Britain

The RHS treats a conventional lawn as a March-to-October job, weekly or fortnightly, and about weekly in summer if it is growing. In a drought you mow less. Do not mow wet grass or a frost. Woodland Trust figures from Nature’s Calendar put an average UK first cut around 19 March across 2000–2025. That is a citizen-science average, not a date you must be on the lawn. Wait for a dry day and grass that is actually growing. If the mower is already in the shed, set the height before you start the motor.

How much to take off

The RHS one-third rule is the practical limit. Take off no more than about a third of the leaf in one pass. The ordinary targets are about 4 cm in spring, autumn and winter, and about 2.5 cm in summer. A fine lawn is about 6–13 mm. Those are RHS heights, not inch figures from other sites. The swift states 30–50 mm, so it cannot reach 2.5 cm. Most other stated minimums are about 20–25 mm. Only the Hover Vac 250 states 11 mm, on a 25 cm hover. The Speedi-Mo bullets say 20–60 mm while a cell says 20 cm. If the lowest click is above the height you wanted, raise the target or look at another row. Several higher passes beat one scalp.
Flymo Flymo Speedi-Mo 360C

Testsieger

Flymo Flymo Speedi-Mo 360C
9.2/10about £110
View offer

The first cut and long grass

If the sward is rank, strim the worst of it first, or take two or three high passes over a fortnight. Hyundai HYM3313E and Ark Mat reviews include the motor cutting out. That can be a fault, and it can be a first cut that is simply too heavy. Unplug the mower, or take the battery off, before you lift the flap or reach under the deck. A light deck does not change the one-third rule. Wet grass clogs a 15 L hover box even faster than a 30 L bag, and Electrical Safety First is explicit that dew counts as wet.

The lead, the RCD and the blade

A cut lead can kill. Use an RCD and keep the cable on grass you have already cut. An extension has to be an outdoor lead, fully unwound, with a thermal cut-out, and it must not be plugged into a second extension. A reel that stays coiled can be rated far below the 1,200–1,600 W these corded mowers state. If the lawn is further than a stated 10 m or 11 m lead, stop. Do not daisy-chain. The Speedi-Mo and the Bosch do not state a lead length, so measure what arrived before you assume it reaches the far edge. Unplug, or remove the battery, before you clear grass, check the blade, or turn the mower on its side.

Common questions

How often should I mow from March to October?
The RHS says weekly or fortnightly through that season for a conventional lawn, and about weekly in summer while the grass is growing. In a drought, leave it longer between cuts. Skip wet days and frost. No Mow May is optional, for a patch you are treating as meadow, not a rule for a lawn you still want short. There is no fixed weekday in the guidance.
What is the one-third rule?
Do not take more than about one-third of the grass height off in a single pass. If you need to come down from a long spring sward to a summer height, do it over more than one cut, on later days, starting higher. One low pass that exposes soil is not a shortcut. The rule is about the leaf, not about how many minutes you hoped the job would take.
When do I do the first cut?
When the grass is dry and growing, not on a calendar average. Nature’s Calendar puts a UK average around 19 March, and that is not a deadline. Set the mower higher than usual, about 0.5 cm on the RHS March note, and clear stones first. If the lawn is rank, strim or take several high passes. The highest setting on day one beats the lowest click.
Can I mow wet grass?
No. The RHS says not to mow wet or frosty grass, and Electrical Safety First includes dew in that warning for a mains mower. Wet clippings clog the deck and the box, and a damp lawn plus a lead is a shock risk if anything is damaged. Wait for the surface to dry. A light machine is not an exception. Lifting it more easily does not make the grass safer to cut.
What if the motor cuts out on long grass?
Stop, isolate the mower, and clear the deck only once the plug is out or the battery is off. A cut-out on the Hyundai 33 cm or the Ark Mat can be a fault, or a first pass that took too much leaf. Do not lean harder on the handle. Raise the height, let the machine cool, and take less off. Smoke or a switch that trips on short dry grass is a reason to return it, not to finish the stripe.

Related pages

Lawn mower buying guide

Lawn mower for a small garden

Best lawn mower

Lawn mower

Cordless vs corded lawn mower: runtime and the lead

Sources

Public UK sources from the research digest. amazon.co.uk prices, stars and review counts are the saved listings for this set. No lab test was run.

  1. GOV.UK outdoor-noise guidance
  2. Schedule 3, Noise Emission Regulations 2001
  3. GOV.UK Supply of Machinery (Safety) Regulations 2008
  4. Electrical Safety First: lawnmowers
  5. HSE electrical equipment
  6. RHS: lawn mowing
  7. RHS: how to mow a lawn
  8. GOV.UK noise nuisances