Why Does Some Mulch Smell Like Manure?

Have you ever noticed that mulch has a very distinct smell? It is often compared to the smell of manure, but why does it smell like this?

In this blog post, we’ll take a look at the science behind the smell of mulch and how adding mulch to your garden or yard can help you create a healthier environment.

The Science Behind the Smell of Mulch

Mulch is made up of materials such as bark, leaves, grass clippings, sawdust, and even manure.

These materials are used to provide protection for plants in the form of insulation from extreme temperatures and moisture retention for dry conditions.

But these same materials are also responsible for giving mulch its characteristic odor.

The scent of mulch is actually caused by anaerobic bacteria which are present in all organic matter.

As plant material breaks down over time due to exposure to air, water, and other elements in the environment, it releases gases including carbon dioxide, methane, and sulfur compounds.

These gases are what give mulch its distinctive “manure-like” smell when they escape into the air around us.

Mulch also provides a great habitat for beneficial organisms such as earthworms, fungi, and bacteria which break down organic matter into nutrients that can be absorbed by plants.

This helps improve soil fertility and drainage as well as aeration which makes it easier for roots to access nutrients from the soil.

Adding mulch to your garden or yard will not only make it look attractive but also help create a healthier environment for plants by providing necessary nutrients for growth and keeping weeds at bay.


Mulch has many benefits for your garden or yard but one thing that comes along with it is its distinct scent.

While some may find it unpleasant, understanding why mulch smells like manure can help us appreciate its importance in creating healthy environments for our plants.

Not only does it protect them from temperature extremes and moisture loss but also provides essential nutrients that keep them healthy and thriving!

READ MORE: Will mulch kill weeds under it?

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