What does mulching do on a lawn mower?

How mulching works

On a normal mower, the blade cuts the grass and airflow throws the clippings back into the grass box. To mulch, you fit a mulching plug (a shaped insert) into the chute, or on some mowers flip a lever. The chute is closed, so the clippings circulate under the deck and are cut several times before they drop down between the grass blades.

Some mowers use a dedicated mulching blade with extra cutting edges or a curved profile to keep clippings in the air for longer. Others rely on the standard blade and the shape of the deck. Check your manual to see whether your mower needs a different blade for mulching.

1. 1

   Remove the battery and safety key.

2. 2

   Remove the grass box.

3. 3

   Fit the mulching plug into the chute, or set the mulch lever, as the manual describes.

4. 4

   Fit a mulching blade if your mower needs one.

5. 5

   Refit the battery and mow at your usual height, in dry conditions.

What mulching does for the lawn

Returning clippings is widely recommended by lawn experts, including the RHS, as long as the clippings are short. Fine clippings break down quickly and return nutrients, notably nitrogen, to the soil. They also act as a thin layer that helps reduce moisture loss in dry spells.

The practical benefit is just as important: no grass box to empty, and no clippings to bag or compost. On a larger lawn this saves a lot of stops. The trade off is that the mower works harder, which uses a little more battery than collecting.

• Returns nutrients from the clippings to the lawn.
• Helps the soil hold moisture in dry weather.
• No grass box to empty or clippings to dispose of.
• Uses slightly more battery than collecting.

When to mulch and when to collect

Mulch when the grass is dry and you are only taking a little off. Follow the RHS one-third rule and do not remove more than a third of the grass height in one cut; our one-third rule tool shows how low you can go today. Short clippings disappear into the lawn; long ones sit on top in mats.

Collect when the grass is wet, long or the first cut of spring, and in autumn when leaves are falling. Wet clippings clump, stick under the deck and can smother the grass. Collecting also gives a tidier finish before an event, and lets you see when the lawn is clear.

Mulching on a damp UK lawn

The UK climate makes mulching harder than in drier countries. Morning dew and frequent showers mean grass is often damp, and wet clippings will not mulch cleanly. If you want to mulch, mow in the afternoon once the dew has gone, and mow more often so each cut is small.

Clean the deck more often when mulching, because fine clippings build up under it. With the battery and key removed and gloves on, scrape it out after each session. A build up adds drag, and can trip a cordless mower's overload cut-out. Our cordless mower not working guide covers that symptom.

Note:Remove the battery or safety key before you touch the blade, clear the deck or tip the mower, and wait for the blade to stop completely. Wear sturdy gloves, as the blade edge stays sharp. Never tip or lift a running mower. Charge batteries only with the maker's charger, away from heat, and stop using any pack that is swollen, cracked or very hot. If in doubt, ask a dealer or service agent.

Cordless mowers with mulching

Many battery mowers in our guides include mulching. The Greenworks 40 V 41 cm mower is listed with 2-in-1 mulching or collection into a 50 L bag. The Ryobi ONE+ mower and trimmer kit includes a mulching plug and 35 L grass catcher. The Yard Force 40 V 37 cm has a mulching plug and a rear roller. The Makita DLM462PT4 is listed as 3-in-1 for cutting, collecting and mulching.

For more options, see our best cordless lawn mower guide and small garden cordless mower guide. Robot mowers mulch all the time by design, cutting a little every day; our best robot lawn mower guide explains them.

Compare mulching cordless mowers →

Frequently asked questions

Is mulching better than collecting? On dry grass cut often, mulching returns nutrients and saves time. On wet or long grass, collecting gives a cleaner result.

Does mulching cause thatch? Short clippings break down quickly and are not the main cause of thatch. Long clumps left on the surface are a problem, so mulch little and often.

Do I need a special blade to mulch? Some mowers only need the mulching plug, others recommend a mulching blade. Check the manual for your model.

Does mulching use more battery? Usually a little more, because the blade cuts each clipping several times. Mowing dry grass and taking small cuts keeps the extra load down.