Mulching with Cardboard | Pros & Cons

Mulching with cardboard is a fantastic way to start a no-dig garden. Cardboard will smother weeds, keep moisture in the soil and is a cheap way to make garden paths. Cardboard can be used as a base under mulch to improve your soil and encourage worm and microbe growth.

This article will explore how to mulch with cardboard at home including the pros and cons.

Mulching with Cardboard – Pros

Cardboard smothers weeds

Cardboard is fantastic for smothering weeds and forms the first layer of the no till garden method. When using this method, layers of cardboard are placed over weeds which will stop them from getting light and they will eventually die off under the cardboard. This is particularly good for soft weeds that do not have runners like clover and chickweed.

Layer the cardboard without leaving any gaps and place it straight over the weeds. Layer compost, straw or wood chips over the top of the cardboard to hold it in place and stop it from drying out. The cardboard will break down over time killing off the weeds. This will create fantastic soil to grow fruit trees, vegetables or flowers.

To start a no dig garden, check out this great video below that uses cardboard as a mulch.

Cardboard adds organic matter to improve your soil

Cardboard is a high carbon material and contains air pockets between the layers. This allows microbes to come in and start breaking down the cardboard into your soil. Worms will be attracted to both the cardboard and the bacteria and will continue the breakdown process.

Check out this video for a quick guide to using cardboard in your garden as mulch.

Laying cardboard down as a mulch will help to keep moisture in the soil creating the perfect environment for microbes and worms to thrive.

Mulching with Cardboard – Cons

Cardboard can be plastic coated

Some cardboard contains a plastic coating and colored ink which will get into your soil and take a long time to break down. Adding this to your garden can cause moisture build up and you could be adding chemicals into your garden that you don’t want. Choose plain cardboard to use as mulch in your garden instead.  

Boxes with a plastic coating are not great for mulching.

Cardboard can be covered in tape

Depending on the box structure some cardboard can be closed with plastic tape. This is common for moving boxes where they have been closed at home using packing tape. You should remove the tape from the cardboard before putting it in your garden. The tape will take a long time to break down and can end up in your soil.

Cardboard can attract bugs

Anytime you lay something flat on the soil surface it becomes a hiding place for insects and creatures. You may find that slugs, snails, spiders, lizards and ants can all enjoy living underneath your cardboard. While this is not a problem, be very careful if you live in an area with snakes as they may make a home under the cardboard as well.

To be as safe as possible, do not lift the cardboard with your hands, particularly in warm weather. You should not need to lift your cardboard at all as once it is laid you should put wood chips or straw over the top to hold it down.

Use cardboard instead of weed fabric

Cardboard is the perfect way to stop weeds from growing through your garden beds. Brown, thick cardboard can be laid on your soil and topped with compost or bark mulch. To create a fantastic vegetable garden bed layer compost and straw mulch and allow it to break down.

Using cardboard to create paths

Using cardboard as a base to create a natural, movable path is a fantastic idea. If you have an area between vegetable garden beds or down the side of your house that you would like to turn into a path then using cardboard is a fantastic way to do this.

Step 1: Pick the area that you want to lay the path and rake the area flat.

Step 2: Cut the cardboard into the shape of the path and lay it down where you will want to walk.

Step 3: Lay bark chips over the top to hold the cardboard in place.

This simple method of making a path using cardboard is a great way to stop weeds from growing through. The cardboard will stop the weeds from getting light and growing through your bark chips. Make sure that you don’t leave any gaps when laying your cardboard and it will work well.

Check out this video for more on making paths with cardboard and wood chips in your vegetable garden.

Different types of cardboard to use in the garden

Cardboard comes in many thicknesses, coatings and colors and some are great for using in the garden. Amazon boxes are a thin cardboard with minimal ink on them so they are a great choice. Flattening out plain shoe boxes or other plain cardboard is also a great choice.

Cereal boxes are fine to use in your garden and will break down. Most will be Tissue boxes and cookie boxes also come with a plastic coating so are not a great choice for your garden.

Egg cartons are a fantastic carboard for your garden as they are a soft cardboard and will break down quickly.

Egg cartons made with plain cardboard can be a great mulch or added to your worm farm

Mulching safely with cardboard

To mulch safely with cardboard choose a cardboard that is plain and does not contain large amounts of ink. Some cardboard can contain a plastic coating or adhesive and will take much longer to break down. Egg cartons and plain brown cardboard make great mulch in your garden.

How long cardboard takes to break down in a garden

Cardboard can take anywhere from 3-6 months to break down in your garden. This will vary depending on how thick the cardboard is and the conditions. In warm moist conditions cardboard will be broken down in around 3 months if laid under bark chips or compost. Microbes and worms will break down the cardboard and mix it in with the soil.

Using shredded cardboard as mulch

Shredded cardboard can be a good mulch if mixed with wood chips or compost. Shredded cardboard on its own will become too dry and can blow away. Mix it together with other mulch types to hold it in place.

Mulching with cardboard – Summary

Cardboard is a low cost or completely free way to stop weeds and mulch your garden. When used in combination with bark chips it can make a fantastic path or no dig garden. Keep moisture in your soil and support microbe growth by laying cardboard as a mulch in your garden.

Happy mulching.