Mulching blades do not work properly with side discharge chutes
Mulching blades are designed to work only with a closed deck and a mulching chute or bag. When you attach mulching blades to a mower set for side discharge, the blades will still cut grass, but they will not mulch it. The grass exits the side chute as whole clippings instead of being chopped into fine pieces and redeposited on the lawn.
The reason is mechanical. Mulching blades have a curved design that lifts clippings upward and recirculates them through the cutting chamber multiple times. A side discharge chute bypasses this chamber entirely—clippings go straight out the side opening before the blade can process them. You lose the mulching benefit and end up with the same scattered windrows you would get from standard blades.
If your mower has a side discharge chute and you want to mulch, you need to either close the chute and attach a mulching kit, or switch to a mower with a mulching deck. Using mulching blades with the side chute open is a mismatch between blade design and deck function.
Key Takeaways
- Mulching blades require a closed deck to recirculate clippings multiple times; side discharge chutes prevent this recirculation from happening.
- Attaching mulching blades to a mower with an open side chute produces the same result as standard blades—whole clippings scattered across the lawn.
- To mulch with a side discharge mower, you must close the chute and install a mulching kit designed for your deck.
- Mulching blades work best on mowers built with a mulching deck from the factory, not retrofitted onto discharge-style machines.
How mulching blades actually work
Mulching blades have a distinctive curved or scalloped edge that creates a vacuum effect inside the mower deck. As the blade spins, it pulls clippings upward and holds them in the cutting chamber longer than standard blades do. The clippings are chopped, then lifted again, then chopped again—sometimes four or five times—before they fall back onto the lawn as fine particles.
This repeated processing requires the deck to be sealed. Air cannot escape through a side chute, or the vacuum collapses and clippings exit before they are fully processed. The closed environment is what makes mulching blades function. Without it, they are just curved blades that cut grass the same way a standard blade does.
What happens when you use mulching blades with side discharge
If you install mulching blades on a mower with an open side chute, the blades will cut the grass, but the deck design works against them. Clippings are pulled upward by the blade curve, but instead of being recirculated, they when ready encounter the open chute and exit the mower. The vacuum effect never builds because air is flowing out the side opening.
The result is clippings that are only partially chopped—some may be cut into two or three pieces, but most will be whole or in large chunks. You will see the same windrows and scattered clippings you would get from standard blades. The mower will not clog, and it will cut normally, but you will not get the fine mulch that makes the process worthwhile.
Your mower will also work harder than necessary. Mulching blades are heavier and more curved than standard blades, which increases blade drag. On a side discharge mower, you are paying the fuel and engine cost of mulching blades without getting any mulching benefit.
Closing the side chute to use mulching blades
Many side discharge mowers have a chute cover or plug that can close the opening. If your mower has one, you can close it and install mulching blades. However, closing the chute alone is not enough—you also need to may support air can escape from the deck in another way, usually through a mulching kit.
A mulching kit typically includes a baffle plate that redirects clippings back into the cutting chamber instead of letting them fall straight down. The kit also has vents that allow air to escape without creating backpressure. Without the kit, closing the chute will cause the mower to clog because clippings have nowhere to go.
Check your mower's manual to see if a mulching kit is available for your model. Not all side discharge mowers can be retrofitted. Some decks are not designed to handle the airflow changes that mulching requires, and forcing the conversion can damage the mower or create a safety hazard.
Standard blades versus mulching blades on side discharge mowers
On a side discharge mower, standard blades and mulching blades perform almost identically. Both cut grass and eject clippings out the side. The main difference is that mulching blades are heavier, more curved, and more expensive. You pay extra for a feature that cannot work on your mower.
Standard blades are the correct choice for side discharge mowers. They are lighter, cheaper, and designed for the way your deck actually functions. If you want to mulch, the solution is not to buy mulching blades—it is to change your mower or retrofit your deck with a mulching kit.
When mulching blades make sense
Mulching blades are worth buying only if you have a mower with a mulching deck or a side discharge mower that you have retrofitted with a mulching kit. They are also the right choice if you are buying a new mower and you plan to mulch regularly. On a properly designed mulching mower, mulching blades will reduce clippings to fine particles and return nutrients to the soil.
If you have a standard side discharge mower and you are considering mulching blades, ask yourself whether you actually want to mulch or whether you are just looking for a different blade option. If you want finer clippings, mulching blades will not deliver that result on your current mower. A mulching kit or a new mower is the real solution.
Frequently Asked Questions
Will mulching blades clog my side discharge mower?
No. Mulching blades will not clog because clippings exit through the side chute before they can accumulate. However, they also will not mulch, so you are using the wrong blade for your mower type.
Can I use mulching blades if I just close the side chute?
Closing the chute alone will cause clogging. You need a mulching kit with a baffle plate and proper venting. Check your mower's manual to see if a kit is available for your model before attempting this conversion.
What is the difference between mulching blades and standard blades?
Mulching blades have a curved design that recirculates clippings for repeated chopping. Standard blades are flat and designed for side discharge. On a side discharge mower, both produce the same result—whole clippings scattered on the lawn.
Should I buy a new mower if I want to mulch?
Not necessarily. If your current mower can accept a mulching kit, that is usually cheaper than buying a new mower. If no kit is available for your model, then a mulching mower or a mower with a mulching deck would be the next option to consider.
Do mulching blades work on bagged mowers?
Mulching blades work best on mowers with a dedicated mulching deck, not on bagged mowers. A bagged mower is designed to collect clippings, not recirculate them, so mulching blades do not function as intended on that deck type either.