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What is grass mulching?

The vast majority of lawn mowers work in the same way: they use a blade to cut grass, blowing the clippings into a collection box at the back, which you then empty into a compost heap or a garden waste bag. The alternative option is mulching, where the grass clippings aren’t collected but are returned to the lawn. Here’s what you need to know about the process.

What is grass mulching?

Mulching is any material spread over the surface of soil and used for covering. There are many types of mulch, but here’s we’re looking at grass mulching specifically. Mulching involves cutting the grass clippings into tiny pieces that aren’t collected in the grass collection box but are returned to the lawn instead. 

It’s not like when you use a grass trimmer and end up with long bits of grass that manually have to be collected; instead, the grass clippings are so small that you won’t even notice them on your lawn, and the bits won’t stick to your shoes.

Why use grass mulching?

Grass is full of nutrients and moisture, so removing these in clippings doesn’t make sense. Using mulching, the clippings break down and return the nutrients and moisture to the soil. It’s estimated that grass clippings contain around 25% of the fertiliser your lawn needs yearly. That saves you money on lawn feed, as well as being kinder to the environment.

Mulching also saves time, as you don’t have to stop to empty the grass collection box on your lawn mower.

What do you need to mulch grass?

You need a lawn mower that’s capable of mulching. Some mulching lawn mowers are designed specifically for this task, but many other models in our guide to the best cordless lawn mowers can be upgraded with a mulching kit, such as the excellent Stihl RMA 339 C

A mulching kit consists of a plug that blocks access to the collection box’s chute, and it replaces the blade with a mulching one: this is designed to cut grass into fine particles. Robot lawn mowers are all designed to mulch, using fine blades to shred the grass, so you never have to collect any cuttings.

Husqvarna Automower 405X underneath

When shouldn’t you mulch grass?

If you’ve got very long grass, such as before the first cut of the season, you should use a traditional lawn mower to remove the cuttings. A mulching lawn mower won’t be able to cut down the grass finely enough, so you’ll end up with long bits of grass on your lawn. 

Mulching does require some vigilance, and you should cut your lawn more regularly than with a traditional lawn mower: that’s the ethos behind robot models, which cut more regularly, but only take a tiny amount off the grass each time.

Be careful if you have lots of weeds on the lawn, too. Mulching will help them spread, so treat your lawn before switching to mulching.

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