Can You Use Sawdust as Mulch? Here’s What You Need to Know

There are a lot of discussions in the gardening world about whether or not sawdust is a suitable mulching material. Some say it’s great for weed suppression and moisture retention while others say it can do more harm than good. So, what’s the right answer?

In short, yes, sawdust can be used as mulch. As long as you’re careful not to let it touch the base of your plants and as long as you add extra nitrogen to your soil to prevent major nutrient deficiencies, sawdust can prove to be quite useful to vegetable gardens.

Read on to learn everything you need to know about using sawdust in your garden and how you can best prevent nutrient deficiencies and damage to your crops. I’ll also share some other ways to incorporate sawdust in the garden without using it as mulch.

Why is mulching important?

In my opinion, mulching is one of the most important things you can do to maintain the life and health of your garden. Several benefits come from mulching and there are so many different materials you can use as mulch.

In short, the purpose of mulching is to protect and improve the quality of your soil. Not sold on mulching yet? Here are just some of the ways that your garden will benefit from the use of mulch.

Weed suppression

Leaving soil exposed makes it much easier for weeds to germinate and spread. By laying down mulch, weed seeds have a much harder time growing through this thick layer of organic matter. It also limits the amount of sunlight that reaches the soil surfaces, limiting the growth of weeds.

Moisture retention

Laying down a good layer of mulch locks moisture into your soil to help prevent it from drying out during the hot summer months. Making sure your soil stays adequately moist will help to prevent stress among your garden plants.

To learn more about moisture levels and keeping your plants hydrated, check out this article on the best time of day to water your plants. 

Erosion control

Exposed soil also has the risk of being washed or blown away through natural occurrences like rain or wind. But, topsoil is crucial to the health of plants because it’s where they get most of their nutrients from. A good layer of mulch will help prevent weather from wearing away your topsoil.

Soil temperature regulation

Much like me and you, plants need temperature regulation within the soil to thrive. Layering mulching over your garden in the winter helps to keep the soil warm until it’s time to plant again in the spring. Similarly, mulching your garden in the summer helps to keep the soil cool.

Addition of organic matter

Lastly, adding organic mulches like straw, shredded paper, wood chips, dry leaves, or sawdust will give your soil a healthy boost of nutrients. As these mulches break down over time, their nutrients get added back into the soil and become new organic matter. 

How to use sawdust as mulch

Sawdust has the potential to provide all of the above-mentioned benefits to your garden, but only if incorporated properly. 

The first thing I’ll say about using sawdust as mulch is to not let too much of it touch your plants. Especially around shrubs or trees. Leaving sawdust built up around the bottom of your plants can cause burns and ultimately kill them.

To prevent this from happening, create a ring of mulch about an inch or two from the base of the plants so that it is not touching them. 

Sawdust is a great mulching option for plants that love acidic soils because it can lower soil pH. You can use sawdust to mulch around the base of plants like blueberries, azaleas, hydrangeas, and nasturtiums to make the soil more suitable for them. 

Sawdust tends to break down relatively quickly so it will have to be consistently reapplied as needed. If you’re able to see your soil or weeds start poking through, it might be time to reapply. You can expect sawdust to break down in about four to six months. 

My preferred way to use sawdust as mulch is to mix it in with something like straw or dead leaves. That way, I don’t have to worry too much about over-applying the sawdust and causing major nutrient deficiencies in my garden. 

It can also be difficult for me to find enough sawdust to cover my whole garden so having a supplemental mulching option proves to be quite helpful to me. 

Preventing nitrogen deficiencies

One thing that can be a concern with sawdust mulch is the potential for nitrogen deficiencies in the soil. As sawdust decomposes, it tends to take up nitrogen, leaving very little in the soil for other plants. 

Nitrogen is an important macronutrient for plants (it’s the “N” in NPK!) and is crucial for a plant’s ability to photosynthesize. If you’re worried about sawdust causing nitrogen deficiencies in your garden, consider adding a nitrogen input to your soil. 

The addition of good compost or a nitrogen-based fertilizer can help prevent any major nitrogen deficiencies within your soil. 

Where can you find sawdust?

If you or someone in your home is a crafty person, then you probably have your own supply of sawdust somewhere. Saving your sawdust from any home project is a good way to build up a sawdust supply.

But, if you’re like me and you’re not very good at woodworking projects, then you’ll have to find a sawdust source elsewhere. There are plenty of places you can check to see if they have sawdust available. 

The first place to look would be with any local sawmills or woodworking shops if you have them in your area. There’s a chance that these places will give you sawdust for free or at a significantly discounted rate. 

If you don’t have sawmills or woodworkers in your area, you can check at any local hardware store like Lowe’s or Tractor Supply where they will have bags of sawdust for sale. 

A note on treated wood

While many of the places I mentioned above are great resources for free sawdust, it’s important to check if the sawdust comes from treated wood. Treated woods are those that have had preservatives added to them in the form of some pretty harsh chemicals in an attempt to increase the longevity of the wood. 

These chemicals can be harmful to plants and humans and therefore should not be used in a garden growing edible food. A quick ask of your sawdust provider will let you know if the wood you’re getting has been treated. 

If you’re using sawdust from wood you have at home, check the tags of your wood. It will be clearly labeled as treated with the chemical additives listed. 

Other uses for sawdust in the garden

There are a lot of other great ways to incorporate sawdust into your garden if you’re not quite ready to use it as mulch. Here are some methods to try!

Sawdust for garden pathways

Our team here at TGH has found great success with using sawdust for suppressing weeds and mulching garden pathways. While you need a lot of it to spread a thick layer on your garden paths, it does compact in time, and forms a nice fluffy ‘crust’ that keeps weeds at bay.

Sawdust is dirt cheap, or free if you can get your hands on it, so you can repeat this process every year. The old sawdust on the garden paths will be semi-composted in a year or two. All you have to do is dig it out from time to time, throw it in your compost pile, and add new cardboard and fresh sawdust to your pathways.

Check this article that explains garden path options in detail.

As brown matter in compost

The second option would be to incorporate it into your home composting system. To make good compost, you need to have the right ratio of green matter to brown matter to water. Green matter includes things like kitchen scraps, weeds, or any other plants pulled from your garden.

Sawdust falls under the brown-matter category but this category could also include newspaper, straw, or dried leaves. The ratio that I like to use in my home compost system is to add three parts brown matter to every one part green matter I put in. 

We have a lot of great articles available about composting so start here if you want to learn more about the compost world:

• What’s the Difference Between Manure and Compost?
• Why Does Compost Disappear Over Time?
• Best Ways to Reuse Old Compost
• What Happens if You Don’t Turn Your Compost?

For root vegetable storage

Another good use for sawdust in the garden is to use it as a storage medium for root crops. In the winter, many of us like to put our root crops in long-term storage to ensure some food for the cold season. 

Similarly to how we might store things like carrots or potatoes in buckets with sand, sawdust can be used in much the same way. To do this, you’ll want to choose a storage container like a large plastic bin where there’s room to lay your root veggies. 

• How To Store Fresh Carrots For Winter
• How to Store Fresh, Firm Beets for Winter

Place a layer of sawdust in the bottom of your storage container and then place your veggies on top. Make sure they’re not too close to each other to help prevent rot. Then you can add another layer of sawdust to cover them.

This probably goes without saying but make sure to wash your veggies very well after they’ve been stored in sawdust. This way you won’t end up eating any by accident. 

To recap, sawdust can be a great mulch option, but only if you use it properly and take the necessary precautions to prevent plant burns and major nutrient deficiencies.

Creating a sawdust-free ring about an inch or two from the bottom of your plants will prevent the sawdust from burning your plants. Also, adding a boost of nitrogen fertilizer to your soil will help prevent nitrogen loss from the sawdust. 

Everyone has their own opinions about whether or not sawdust should be used in the garden. But at the end of the day, it all depends on what works best in your garden. If sawdust seems to be doing more harm than good, try a different mulching method.