Guide

Mowing in wet grass: clippings caking under the deck, and what owners do about it

Wet grass sticks to the deck and clumps on the lawn. What owners who mow wet most of the year do: cut little and often, test the grass tops, avoid standing water, clean the underside on a schedule, and where the trouble moves to slopes and turns.

Models: Cross-model
Last updated: 24 Oct 2026
Affects: Robot body — not the app

Cross-modelDetails

Models: Cross-model
Last updated: 24 Oct 2026
Affects: Robot body — not the app

What to do next

If you can, wait until the grass and the ground are dry, and start after the morning dew has gone. If the ground is muddy or the mower leaves wheel tracks, pause and mark that part as a No-Go Zone until it recovers.

Stop and get help if
do not leave it running through standing water or mud.

More about this step

Applies when: the grass or the ground is wet.

Worked if: no wet clippings built up under the deck, and no tracks in soft ground.

Didn't work? Next: step 2 — Mow more often and take less each time. An owner who mows in wet...

Method: Mammotion's own fall-care post
Mow more often and take less each time. An owner who mows in wet grass takes only 10 to 15 mm every second day; another says the mower does best when it is only removing a couple of days' growth. If the grass has got long after rain, raise the cutting height for the first pass and cut lower on a second pass.

More about this step

Applies when: clippings drop in clumps, or the underside is caked after a wet mow.

Worked if: fewer clumps on the lawn and less caked under the deck.

Didn't work? Next: step 3 — Judge wetness by the tops of the grass, not the soil. An owner's...

Method: owners in two threads, in Ireland, the UK and Australia
Judge wetness by the tops of the grass, not the soil. An owner's test is whether the tops are dry, and says the blades below being wet matters less. Keep the mower out of standing water and mud: one owner who let it run through puddles had clippings jammed under the blade guards so badly the guards had to be partly taken apart to clean.

Stop and get help if
do not leave it running through standing water or mud.

More about this step

Applies when: you cannot always wait for a dry day.

Worked if: the mower mows on days that look wet without clogging.

Didn't work? Next: step 4 — Clean the deck and the blade area after wet mows. Owners put it...

Method: owners in the first thread
Clean the deck and the blade area after wet mows. Owners put it at weekly when mowing wet, or about every 10 days to a fortnight for lighter use. An owner who let it go says the height-adjustment error appeared until the underside was cleaned.

More about this step

Applies when: you mow in wet grass at all.

Worked if: clippings never build up enough to jam the cutting height or the blades.

Didn't work? Next: step 5 — If the lawn has slopes, expect the trouble to move from the deck...

Method: five owners' accounts across the two threads
If the lawn has slopes, expect the trouble to move from the deck to the turns. Wet ground tears under turning wheels. Mow those parts when the ground is firm, and read the page on turns tearing up the lawn.

More about this step

Applies when: the grass is torn at the turns or the wheels are caked with mud.

Worked if: you spot lawn damage as a turning problem, not a cutting one.

Method: an owner's account of slopes in the second thread

On this page

What to do next
The problem
What Mammotion says
What owners do
Where the trouble moves
Sources

Mammotion says wait; owners often cannot. Mammotion's own fall-care post tells owners to wait until the grass and the ground are dry¹¹. Owners in wet climates disagree about whether that is possible. What follows is what Mammotion says, and what owners who mow wet say they do, from three threads in October 2026.

The problem

A LUBA 3 AWD owner in Ireland, where the grass is wet most of the year, finds that waiting for it to dry lets it get too long, and then chunks of grass are left behind; mowing wet, grass sticks and builds up under the mower where the blades are. Others in the thread say the same¹. A LUBA 2 owner says it clogs within minutes in wet grass⁷, and another owner puts it more generally: most robot mowers, with spinning blades and no suction, handle wet grass worse than conventional mowers do⁸.

What Mammotion says

Mammotion's fall-care post, from its own account, says to wait until the grass and ground are sufficiently dry, because wet conditions can build up grass under the mower, clog the cutting disc, reduce traction and damage the turf¹¹ ¹². It suggests scheduling after the morning dew has gone¹¹, and, if the ground is muddy or the mower leaves wheel tracks, pausing and marking that area as a No-Go Zone until it improves¹³. A Mammotion staff account repeated the advice in a later thread and added that the guard and the area around the cutting disc should be checked and cleaned regularly¹⁵.

What owners do

Cut little and often. One owner in Queensland mows wet grass every second day and takes only 10 to 15 mm⁴. Another says the mower does best when it is only removing a couple of days' growth¹⁰. Another says to mow as often as you can, especially the day or morning before rain, to raise the height for the first pass after several rainy days, and then to change the angle of the path on later passes³.
Use the highest height and fastest speed for a quick trim, then a second pass lower. An owner in Ireland does that after a few dry days, so the mower trims the lawn quickly before the rain returns¹.
Test the tops of the grass. One owner's rule is that if the tops are dry, the mower is fine, whatever the blades below. The same owner learned not to mow through standing water, which jammed clippings so hard under the blade guards that they had to be partly disassembled².
Expect the guard to clog even when you mow dry. A LUBA 3 owner at the minimum 25 mm height, mowing every 2 to 3 days and starting tasks by hand when the grass is dry, says the guard brackets still fill with grass every two weeks. The discs then fail to return to position and the mower throws an error¹⁴. An owner in Ireland, where it rains most of the year, blows the mower out with an air compressor every other day¹⁶.
Clean the underside on a schedule. One owner scrapes the deck at least weekly when mowing wet⁹, another cleans about every 10 days. An owner in the UK says that if it is left, the height adjustment eventually errors out and forces a clean⁵. The deck page covers what to look for when you clean it: blade and deck maintenance.

Where the trouble moves

The deck is the easy part. On slopes, an owner who has used a LUBA mini 2 says that if the mower must turn on a slope, tank turn or multi-point, it will tear the grass and the wheels will fill with mud⁶. That is the same tearing described on the turns page, and wet ground makes it worse.

If you mow wet and see a pattern, such as a particular height that does not clog or a turn that always tears, tell us.

Sources

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