Guide
Do robot mowers collect grass?
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In short
No, robot mowers do not collect grass. They cut little and often, so each clipping is a tiny piece that drops into the lawn and breaks down quickly, a method called mulching. Clippings only become noticeable if the grass has grown long between runs, so the answer is usually to mow more often, not to collect.
Products for this job
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Check price on AmazonAffiliate linkMammotion Yuka 1500: 1,500 m² with leaf sweeping
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Many people expect a robot mower to have a grass box, and are surprised to find it does not. Collecting would mean emptying a box every hour or so, which defeats the point of a robot. Instead, robots rely on frequent, light cuts. This explainer covers how that works, why it is good for the lawn, when clippings can be a problem and how to manage the spring flush and autumn leaves.
How robot mulching works
A robot mows a little every day or every other day, trimming just a few millimetres off the grass. The clippings are so short that they fall between the blades of grass and decompose within days. That returns nutrients and moisture to the soil. Because the cut is so frequent, the lawn always looks freshly mown.
Why there is no grass box
A robot's body has to be low, light and stable. A grass box would add weight and need emptying constantly, which would stop the robot working unattended. A few commercial machines and concept models have collected, but mainstream garden robots do not. Some robots, such as the Mammotion Yuka 1500 in our guides, add leaf sweeping or collection features, but they are the exception.
Is mulching good for the lawn?
Generally, yes. Short clippings feed the lawn and help it hold moisture in dry spells. It does not cause thatch on a healthy lawn when clippings are short, because they break down quickly. The RHS notes that clippings can be left on the lawn when mowing frequently in summer.
When clippings become a problem
Clippings only show when the robot cuts long grass. That happens in the spring flush, after a break in the schedule, or when the robot has been off due to rain. Long clippings can clump and sit on top of the lawn. They can also get trodden indoors.
| Situation | What to do |
|---|---|
| First cut of spring | Mow with a normal mower and collect, then start the robot |
| Fast spring growth | Increase the robot's running hours |
| After a wet spell | Let the robot catch up over a few days on a higher setting |
| Autumn leaves | Rake or blow them off; robots shred only light leaf fall |
Setting cutting height and hours
Set the height a little higher at first and lower it gradually over a couple of weeks. Make sure the robot runs enough hours for your lawn size; an under sized robot struggles to keep up in May and June. Our lawn-area calculator helps check that the rated area fits your lawn.
Dog mess, leaves and debris
Robots do not collect anything, so they also spread anything left on the lawn. Pick up dog mess before scheduled runs. Clear fallen fruit and heavy leaf fall in autumn, as wet leaves clog the deck. Small amounts of light leaf fall are usually shredded without trouble.
If you prefer a collected finish
If you like a striped, collected lawn, a cordless mower with a grass box and rear roller may suit you better, or you can use one alongside a robot for a special occasion. Our robot mower vs cordless mower comparison explains the trade off.
Mulching and lawn health
Mulching suits most lawns, but a few situations need care. If your lawn has a lot of moss or thatch, scarify in autumn and let the robot mow little and often afterwards. If you have weeds that spread by seed, such as some lawn weeds in late spring, short frequent cuts actually help by stopping them flowering.
In very dry weather, raise the cutting height and reduce the robot's hours. Longer grass shades the soil and the fine clippings help hold moisture. In autumn, when growth slows, reduce the schedule and stop for winter once growth ends.
If you are choosing a robot for a large lawn, make sure its rated area is comfortably above your lawn size, so it can keep up with growth and keep the clippings short. Our guide to robot mowers for slopes also lists rated areas for each model.
Frequently asked questions
Do robot mowers leave clippings on the lawn? Yes, but they are tiny and break down quickly, so they are rarely noticeable.
Is there a robot mower with a grass collector? Mainstream garden robots do not collect grass. A few add leaf sweeping as a separate feature.
Do robot mowers cause thatch? On a healthy lawn, frequent short clippings decompose quickly and are not a significant cause of thatch.
What about the first cut of spring? Use a conventional mower with a grass box for long grass, then let the robot take over.
What you need
- Check price on AmazonAffiliate link
Ecovacs Goat O1000 RTK: wire-free, about 1,000 m²
- Check price on AmazonAffiliate link
Gardena Sileno minimo 250: UK plug, 57 dB(A)