Lawn mower not mulching properly – How to Fix It

Mulching lawn mowers help to keep your lawn healthy and green by recirculating and re-cutting the grass clippings under the mower deck to produce a fine mulch. The mulch setting is an option on your mower, so you can decide to use it or not.

The special curved blade that will mulch your grass has several sharp edges that cut the grass clippings into small pieces as it moves under the mower. Mulching blades are designed to chop the grass finely and drop it back on your lawn to help feed your lawn. These blades are only designed for this specific purpose, but they can stop working properly because of several factors like a dull or damaged blade, wet or long grass, or a slipped clutch.

Different types of mowers that can include mulch settings

Type of mower
Powered by
Mowing capabilities
Push mowers
Gas or electric
Self-propelled mowers
Gas or electric
Zero-turn ride-on
Electric or gas
Lawn tractors

Reasons why a lawn mower won’t mulching properly

Damaged blade

A damaged blade will not only affect grass cutting but also the collection of the grass clippings. When mowing the blades may hit sprinklers, toys, stumps, stones, and rocks which can bend and damage the metal blade. The blade may be okay, but it could be worn-out. Don’t repair or bend the blade because it’s specially treated and interfering with it can cause it to shatter. A bent blade can cause vibrations that can damage your engine and lawn scalping. When replacing a blade get a new bolt and washer.

Dull blade

If the mulching blades are dull, they’ll leave uncut grass and damage your lawn. It will tear the grass and leave it with jagged edges that will turn the grass tips yellow. To avoid this, sharpen your blades at least once per season or more times if needed. There are 2 main types of blades, mulching blade, and the lift blade.

Mulching blade. Designed to finely chop and disperse grass clippings. Most of the latest lawn mowers are designed with a hybrid mulching blade also called 3-in-1 because it will collect, discharge, or mulch. These blades are ideal for regular dry weather cutting but might struggle if the grass is tall. Mulching blades work well when the grass is cut dry, in small amounts, and regularly.

Lift blade. This is a 2-in-1 blade for collection and discharge. This blade uses a lot of power and a higher lift blade will need a mower with a more powerful engine. The trailing edge of the blade curves upwards creating a lift, so the steeper the curve the more powerful the lift. You can use these blades to bag wet or dry grass.

Slipped clutch

Tractor mowers are fitted with a clutch system that transfers the engine power to the blades. If the clutch fails to start, it slips and this causes the blades not to turn with the normal speed and power. You will notice this when you’re trying to cut tall thick grass. Some walk behind mowers also use the cutch setup where you use separate controls to engage the blades, but this system is cable operated so you’ll only need to adjust the tension on the cable. If you don’t have a clutch but have a separate lever to control the blades, your blades are controlled by a tensioned belt, and pulling the bail lever will tighten the tension in the belt which will make the blades spin.

Tall and wet grass

Ideally, your mower shouldn’t cut grass that is more than one inch and tall grass is a tall order on your mower, especially if you want it to cut the lawn tight with just one cut. Tallgrass will cause your mower to clog which will affect its cutting quality. If the cutting height is set too low, you can adjust the height. To keep your grass short, cut regularly, and clean your mower deck to remove any dry grass to prevent it from clogging. You can also coat under your deck with a non-stick coating to prevent clogging.

Grass is a lot heavier when wet and most mowers will have a hard time mulching wet grass because it will tend to stick underneath the deck. This will cause clogging and the blades will not be as effective as they should. The bottom line is mowers don’t cut wet or tall grass very well, so it’s best to stick to cutting dry grass.


Mulching will not only reduce your work, it will also help the mulch to breakdown faster into organic fertilizer for your lawn. If you hate raking and bagging grass clippings after mowing, mulching is the best option.


How long do mulching blades last?

Most mower blades can last about 20-25 hours before they need to be sharpened. Their overall lifetime is about 100-200 hours and some even last 400 hours.

Is it better to mulch or bad leaves?

Shredding leaves with a mulching mower will save you time and money and the decomposing leaves and grass provide cover to the soil.

William Smith

William Smith has been rendering his services to a botanical garden for the better part of his adult life and has recently moved to landscaping firms. His love for gardens has been nurtured since he was a kid, evident from the various garden centers and estates that have benefited from his services. Smith is a natural when it comes to gardening and when combined with his acquired degree in landscape design, you can expect a high-quality professional job, thanks to his experience and expertise. During his free time, Smith does gardening as a hobby and runs forums where he offers expert ideas on gardening.

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