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Why Does Mulch Smell Like Poop – with 3 ways to fix it!

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Are you absolutely tired of the horrible stench that is coming from your garden after applying a fresh layer of mulch and you are wondering why does mulch smell like poop?’ Who wouldn’t!

That stuff can smell horrible, one could even say that it smells like poop. Have you been wondering ‘why does mulch smell like poop?’ Why something that is so good for your soil and plant smells this horrible? Well then keep on reading cause we’ll be telling you exactly ‘why does mulch smell like poop?’.

As growers, we all have preferences for what our garden looks like. Some prefer a neater look, while others like to add a splash of eccentricity to theirs’. But no matter what you want your garden to look like, one thing we all have in common is that we don’t want our gardens to reek of poop.

This goal can be hard to achieve when the mulch we add to help the plant in growing gives off the worst scent ever. So not only will we be telling you ‘why does mulch smell like poop?’ but we’ll also be helping you in ridding you of this huge dilemma. 

Why Does Mulch Smell Like Poop
Mulch via Flickr

Why Does Mulch Smell Like Poop?

Some people think this may be because mulch contains manure in it but that’s untrue. Mulch doesn’t contain any manure in it and the reek coming from it can actually be because of the following reasons:

The Mulch Has Become Anaerobic

Most of the time your mulch stinking like poop can be because of anaerobic conditions in it. It’ll smell like rotten eggs, strong vinegar, or even ammonia. Well, that’s a trio of scents to haunt you but adding these to the smell of manure already coming from the mulch can make anyone upset.

This can especially occur in commercial mulch which is produced in huge amounts and can be at times ill-packed. The airtight bags also contribute to perfecting the anaerobic conditions.

When the mulch decomposes in such conditions it produces acetic acid or hydrogen sulfide, which is what produces the odor. But that is not the only harmful factor, since this decomposition also causes the pH to fall from 6.0 to 2.0 which does more harm to your plant than any good the mulch could’ve done.

Decomposition Of Mulch

If your mulch smells like poop, another reason for it can be its decomposition, especially if it’s organic. This happens because of the microbes like bacteria and fungi present in the mulch. You can solely blame the actinomyces for this.

Actinomyces thrive in anaerobic conditions and break down the organic matter to produce humus, carbon dioxide, heat, and water. On rare occurrences, they also produce some chemicals that cause a foul smell in your garden which can be confused for manure.

However, actinomyces are also very beneficial for the plant as they produce some very important nutrients.

They play a major role in the decomposition of complex mixtures of polymer in dead plants, animals, and fungi, which results in the production of some very important extracellular enzymes that help with crop production.

They contribute to biological buffering of soil, nitrogen fixation, breakage of strong hydrocarbons in soil, etc.

The smell produced by the decomposition of mulch is not as strong as when this decomposition happens in anaerobic conditions.

Colored Mulch Can Smell Bad

If you are using colored mulch, then that can also explain any presence of a foul odor. The dye in colored mulch can produce red oxide. It does produce rust alike scent but it isn’t as strong as the foul, manure-like smell produced by the two former cases.

Why Does Mulch Smell Like Poop 2
Mulch Mania – via Flickr

How Should Good Mulch Smell?

A strong and foul odor coming from your mulch is not a good sign. If the scent it’s giving off is rotten, overpowering, and very hard on the nose, then it’s a clear sign that the mulch has gone bad.

Mulch that is in a good condition should smell like fresh compost. Smelling mulch is the best way to define if it’s good anymore or not. If it smells repulsive, then it’s most probably not in good shape, but if it’s giving off a woody scent then the mulch is fresh and good to use.

How To Keep Your Mulch From Smelling Like Poop?

If you’re exhausted from having to smell this pungent scent every time you enter the haven you’ve created in your garden then we’re here to help! Here is how you can prevent this from happening:

Say No To Air Tight Bags!

This will not only help you to prevent any decomposition from occurring in anaerobic conditions but will also help promote a cleaner and plastic-free lifestyle. Poorer air circulation in these bags helps grow the anaerobic conditions within the mulch.

You should make sure that the mulch is well-aerated. Fluff the material up to maximize airflow which will create air pockets in the mulch and help you prevent any foul smell from spreading in your garden.

Spread Your Mulch

This is also a great way to make sure that the mulch is getting maximum contact with air. Spread the mulch in an open area with good air circulation and make sure that the sun hits the mulch so that all toxins such as acetic acid, methanol, or hydrogen sulfide can be removed.

This will help remove any smell that is already present in your mulch.

Use Natural Mulch

If you’re a progressive grower, with a forward-thinking mindset, then using a natural mulch should be your go-to! It is easy to incorporate with growing medium, reduces waste, and is easy to use while also being highly valuable for your plant. Some natural mulch options are cedar bark chips, pine tree bark/straw, etc.


Mulch will start smelling excessively foul and unbearable when it is piled up or anaerobic decomposition is occurring within it. But there are still methods to prevent this from occurring or to solve this problem if it has already started happening in your garden.

It is better to use natural mulch than using store brought/processed mulch to have an eco-friendly gardening experience and also a fresh and odor-less garden!