Should I mow the lawn in winter, and when do I stop?

Why there is no last cut date, how to judge whether a winter lawn needs topping, and the two conditions that make mowing genuinely harmful.

Difficulty: beginner
Time: 20 min
Read: 4 min

Short answer

There is no stop date — grass grows whenever soil is above about 5C, and mild UK winters mean it often keeps growing into December and starts again in February. Top it occasionally at a high setting when it is dry and unfrozen. Never mow frozen, frosted or waterlogged grass.

The idea of a final cut in October comes from a colder climate than the one Britain now has. In most of the country the grass slows rather than stops, and a lawn left long and lush through a mild wet winter lies over, mats down and holds moisture against the crown, which is exactly the condition fusarium and other winter diseases want.

What you'll need

A mower with a high setting
Sharp blade

Mowing height through the UK year, and the one-third rule

Step by step

Watch soil temperature, not the calendar.Grass grows above roughly 5 to 6C at the soil surface. In a mild UK winter that happens on plenty of days between November and February.
Judge by length, not by month.If the lawn has grown noticeably since the last cut and looks like it will lie over, top it. If nothing has changed in three weeks, leave it.
Go into winter slightly longer, not shorter.Around 40mm is a sensible autumn finish. Short grass has less leaf area to make the little energy available and is more exposed at the crown; very long grass mats and holds damp.
Only mow when the surface is dry and firm.Wet ground plus mower weight equals compaction and ruts, and compaction is what causes moss, which is what causes next year's problem.
Never mow frozen or frosted grass.Frozen leaf blades are brittle. They shatter rather than bend, and the crushed tissue turns brown and dies back in patches that show for months.
Stay off frosty grass entirely.Walking a frosted lawn leaves brown footprints for weeks for the same reason. Wait for it to thaw.
Top rather than cut.Raise the mower to its highest setting and take only what has grown. This is a tidying pass, not a cut.
Clear leaves before they mat.A layer of wet leaves left on a lawn for a fortnight yellows the grass underneath and gives you a bare patch by spring. Rake or mow them up — chopped leaves make excellent leaf mould.

Tips

The last cut is whenever the grass last grew. In much of southern England that is often December, and occasionally January.
A mild, wet, still December is the highest-risk period for lawn disease. A long, matted, damp sward is the thing to avoid.
Take the mower in for a service in November when the workshops are quiet, not in April when they are three weeks behind.

Common mistakes

A hard final cut in October to 'set it up for winter' — It removes leaf area at the point in the year when the grass can least afford it and exposes the crowns to frost. Finish the season slightly long instead.
Mowing when the ground squelches — The compaction and rutting caused in one pass takes a full aeration programme to undo.
Leaving thick leaf fall on the lawn until spring — Grass under a wet mat of leaves for three months does not come back green; it comes back as bare soil that moss fills.

If it doesn't work

Brown footprints across the lawn

Cause: Walked on while frosted — Fix: Nothing to do but wait. It grows out in spring. Keep off frosty grass in future.

Grey-white slimy patches in a mild wet winter

Cause: Fusarium patch, favoured by lush, matted, damp growth — Fix: Improve air movement, avoid late high-nitrogen feeds, keep the lawn topped rather than long, and improve drainage.

Ruts and tyre lines after a winter cut

Cause: Mowed on soft ground — Fix: Level in spring by lifting the turf, and only mow in winter when the surface is firm.

Lawn yellow and flattened in February

Cause: Left too long, then matted under winter wet — Fix: Rake lightly to lift the sward, top it high once growth restarts, and feed in mid-spring.

Questions people ask

Is there a date after which I should not mow?

No. Grass in the UK grows on any day the soil is above about 5 to 6C, and that includes many winter days. Cut when there is growth and the ground is dry and unfrozen.

What height for winter?

The highest setting you have, aiming for something around 40mm. You are removing excess, not shaping the lawn.

Does mowing in winter damage the grass?

Not in itself. What damages it is the conditions people mow in — frozen leaf, saturated soil, or a blunt blade tearing tissue that has no growth left to repair itself with.

What about a mulching mower in winter?

Avoid it. Mulching relies on fine clippings dropping through the sward and decomposing quickly, and neither happens in a cold, damp, slow-growing lawn. Box the clippings.