How to put mulch in a compost bin | 7 Mulches

Put mulch in a compost bin with the other ingredients including old compost and food scraps and mix it through with a garden fork. Mulch including straw, dried leaves and sugar cane all be put in a compost bin. Bark mulches like pine or cedar mulch can also be added a compost bin but will take longer to break down.

Bark mulch will take up to 6 months to break down in your compost compared to fall leaves which will only take 1-2 months. Add a variety of mulches to your compost bin for a great mix to add to your garden.

Since I have moved to my tiny townhouse I have been buying pine bark mulch in bags. I also grabbed some more potting mix for my next garden project.

Using old mulch as compost

Old mulch makes fantastic compost. If you have mulch that is partly broken down in your garden bed you can scrape this up and add it to your compost bin. The other option is to dig it into your soil and lay new mulch on top. If there are still larger bark pieces from pine or eucalyptus, I would suggest adding it to your compost bin first. Then you can leave it for a longer time to break down.

Here I have added new pine bark mulch next to older mulch. The old mulch is darker in color and has started to break down. You can also see my first orange Viola for the season,

As the mulch breaks down, it will use up a small amount of nitrogen in your garden bed. A good tip is to add some pelletized chicken manure into your garden bed as you dig the mulch in. This will add extra nitrogen and build up your garden bed full of nutrients at the same time.

Best mulch to put in a compost bin

The best mulch to add to your compost bin is mulch that has been sitting on the top of your garden bed and has begun to break down. If the mulch has already started to turn a dark brown or black color it is already halfway to making compost. It will usually still have some larger pieces in the mix so will still need to be added to your compost to break down fully.

Here are some other great mulches to add to your compost bin:

  • Pine bark mulch
  • Eucalyptus mulch
  • Sugar cane mulch
  • Lucerne mulch
  • Fall or autumn leaves – mix of brown and green
  • Shredded cardboard or paper
  • Chicken manure/straw mix

Mulch that should not be put in a compost bin

Don’t add mulch to your compost bin that is treated with chemicals or pesticides. If you know that mulch has been sprayed for weeds or pests, don’t add it to your compost bin. I would let it break down in a flower bed or under a tree and dig it into the garden bed.

Mulch in Compost Bins – FAQ

Do I need to remove mulch from my garden beds before adding compost?

Once your compost is ready, you will need to scrape back or remove the mulch that is already sitting on top of your garden beds first. You can then add it back on top of the garden bed once you have dug the compost in. The mulch should always sit on top of your garden bed. It will stop moisture from being lost from the soil, protect it from blowing away and encourage worms and microbes. Mulch helps to attract worms to the surface of your garden bed which helps to aerate the soil.

Camelia petals have fallen down around my Hawaiian Snow Bush. These will dry and make a great mulch on top of my soil.

Can I use mulch instead of soil?

You cannot use mulch instead of soil in your garden. Mulch is a fantastic addition to the top of your garden beds to keep moisture in. There are a few reasons why mulch should not be used instead of soil.

  • Water will drain quickly through mulch because it has lots of air pockets. If you plant straight into the mulch, water will run straight through.
  • Mulch is low in nutrients. It won’t have enough nitrogen to support plant growth on its own.
  • Mulch is not as stable as soil. It is lighter so moves around and can expose the roots of your plants.

Can I put mulch in the bottom of my compost bin?

Mulch is a fantastic base for the bottom of your compost bin. You could place shredded cardboard or paper on the bottom layer 3-4 inches thick. A a great choice is pine bark and leaf mix, dried fall leaves and sugar cane mulch.

I’ve added compost first then some pine bark mulch underneath my new strawberry plant.

Mulch will create air pockets at the bottom of your compost bin. This allows air to enter and flow through the rest of your compost. You can then layer on top a small amount of garden soil, vegetable scraps, clean tree trimmings and then more brown materials like leaves and straw.

The addition of mulch on the bottom of your compost bin will also allow good bacteria and worms to find their way into your compost. This will help to break down the compost quickly and prepare it to be added to your vegetable garden or flower beds.

What else can I do with old mulch from my garden?

If you have old mulch from your garden you can add this straight to your compost bin. Mix it in with the compost you have and it will break down over a few months. Old mulch will be partly broken down and part the way to turning into compost. If you see that the color of the mulch had turned darker then that is a great sign, and you know that it has started the break down process.

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