Can I use sawdust as mulch?

by Daniel Berry | Last Updated: 23/12/2020

If you do a lot of woodworking you will inevitably be left with a lot of sawdust and maybe thinking of useful ways to reuse that sawdust. We would all rather reuse something if it can be used well for another purpose, but can you use sawdust as mulch?

Well, that depends, on a few things. Firstly on the wood that the sawdust itself has come from. Different woods will have different pH levels, thus when you use them as a mulch they will affect the pH level of your soil. This can be a positive or a negative thing, depending on the original pH of your soil and also what plants you are trying to grow. Learn more about soil pH level here.

Then there is also the fact that if the wood you are using has been treated then there will be all kinds of chemicals in there. These chemicals can be toxic to your plants, so another thing to watch out for!

Another issue with using sawdust as mulch is that it uses up nitrogen as it decomposes, this draws nitrogen out of your soil. Nitrogen is an essential nutrient for plant growth, so removing it from your soil is not ideal if you want strong healthy plants.

On the other hand, this makes sawdust an ideal mulch if you are trying to suppress plant growth, for instance, if you have a patch of garden that is always full of weeds then using sawdust as a mulch will help kill them off. It will firstly block light from getting to the plant, then it will draw nitrogen out of the soil and finally, it will change the pH level of the soil, potentially hurting the weeds.

For this reason, I would not recommend sawdust for use on plants you are trying to grow but it does make a brilliant weed suppressor.

Hey, I'm Dan, I studied computer science with artificial intelligence at Loughborough University. I try to bring my tech knowledge to the posts where it is needed while also offering a DIY view to go with Sam's professional view on tools. I am a very keen DIY'er and have experience of doing everything the completely wrong way.