Most items that we buy, these days will either be in a cardboard box or there will be an element of cardboard packaging in there somewhere. Modern graphics and printing technology often dresses up cardboard to like something special. We can sometimes be left wondering if it’s cardboard or plastic.
If you are minded to view all materials that you handle with a recycling mindset, then the variety, in appearance, of all the cardboard out there, may leave you wondering what you can do with it.
Most cardboard is recyclable, it can be turned into ‘new’ cardboard. This is done so skilfully, that you don’t realise that the cardboard box that you’re holding, may have been other cardboard boxes in previous lives.
Recycling into ‘new’ cardboard should probably be the first choice of disposal to make the best use of it from a wider community perspective.
But what if you have cardboard that isn’t fit, for whatever reason, to be sent for recycling into ‘new’? Making compost from it may be the only choice left. So, here we ask: is all cardboard biodegradable?
Not all cardboard is recyclable into ‘new’ cardboard but all cardboard is biodegradable. Even if it’s covered with so much print that it’s barely recognisable as cardboard, there will be a fibrous, cardboard element which will break down and disappear into any evolving mass of compost.
Cardboard will become part of the soil
Cardboard is just like wood. All wood is biodegradable. These are transient components of the natural carbon-cycle. Among all the ‘carbon-browns’ that we add to the compost, cardboard is probably the most convenient. Having been formed, originally, from a ground-down log, then pressed into flat panels, we have a ready-made ingredient that does everything that a perfect ‘carbon-brown’ material needs to do.
Does cardboard break down in water?
The thing about cardboard is that, when it’s dry, it can be very strong. Assembled in the right way, it can support a significant amount of weight. But the moment it becomes wet, it will lose all of its strength.
Cardboard will break down in water. It will become soft. It will then extend beyond soft and become a slimy mess. It will lose all resemblances of ever having had any strength about it.
Cardboard juice cartons are often coated in a variety of materials that seal the surface. This is just a surface treatment that usually involves wax or plastic, forming a membrane barrier. The life of this is limited. The protective layer will break down over time and allow moisture to soften the cardboard within.
Cardboard would be no use as a boat-building material. It may work for a short while if it’s been thoroughly coated with an effective waterproofing substance. The same would apply if you tried to mend a hole in a leaking roof. Dry cardboard will be your friend, wet cardboard will become a soggy mess. The best place for wet cardboard is in the compost bin.
Is cardboard a sustainable material?
Cardboard appears to be one of the most sustainable materials that we handle in our day-to-day lives. Cardboard boxes can be reused as complete boxes or they can be opened out into flat sheets to be pulped again and again.
The process of pulping cardboard and pressing it into ‘new’ cardboard is believed to take about half the amount of energy compared to grinding down a whole tree. It also takes considerably less water to make ‘new’ cardboard from old.
The part that we can all play in the cardboard recycling process is to use the recycling facilities that are available to ensure that the sustainable use of cardboard continues.
Does cardboard keep weeds from growing?
As a temporary cover on the ground, cardboard is very effective at stopping anything from growing, including weeds. Any type of cover that stops the sun from seeing the soil will have the same effect. The difference with cardboard is that it will decompose and vanish into the soil.
This is why we have to see cardboard as a temporary weed controller. For a sustained attempt to keep weeds down, you may need to put down 2 or 3 layers.
Spreading sheets of cardboard around in your garden may look untidy to anyone who doesn’t know what you’re doing? Over time, the cardboard will rot down and disappear or this is how it may appear to you.
The underside of the cardboard will be damp, even if it’s dry on the top. This will attract the worms in the soil beneath it. Worms can eat damp cardboard because it’s soft and digestible to them. They will chew at it and convert it to worm casts. All of this is good for the soil and hopefully the weeds will have been slowed down in the process.
There is a warning going around concerning snakes. If you live in a low rainfall district, you will find that the cardboard that you lay down, will survive for a while longer than in damp districts.
This is where you need to look out for snakes. They’re attracted to the damp area between the ground and cardboard. You need to take particular care when lifting up any dry sheets that have been there for a while. Use a long-handled garden fork and just be ready.
Can you use cardboard to kill grass?
Cardboard will kill grass if it can stay in place long enough to stop light and moisture from reaching the ground. Grasses tend to be more resilient than most weeds. Grass will out-survive most plants that are out there. Any attempt to use cardboard to kill grass may result in parts of the grass area surviving. It will depend on how long the cardboard lasts.
From the moment it touches the ground, the cardboard will become damp and then deteriorate. If there are worms in the soil beneath the turf, they will find the damp cardboard and begin eating it. This will become a race against time. If the grass doesn’t expire before the cardboard degrades, then the grass will have a chance of surviving.
If you want to kill grass by placing a sheet of anything over it, a favourite suggestion is black plastic. This won’t deteriorate, nothing will eat it. It will out-last any grass. Why use black plastic? Black plastic will do more than just block out light and moisture. Being black, it will become hot when it absorbs heat from the sun. The heat will build up underneath the sheet and all vegetation, including grass, will be, effectively, cooked.
If you use this method to clear a patch of ground, you can almost be certain that you will kill everything. When you remove the sheet, you will find a patch of bare earth and it will probably be as dry as dust. You may also find snakes, depending on where you are in the world.
About using cardboard in the garden
Is cardboard good for gardens?
Cardboard is an organic material. It will disappear into your garden very quickly. It will leave no trace but will have a good effect. This despite the fact that it’s the product of an industrial process. It’s essentially wood that’s been pulverized into usable fibres that are stuck together to give us a convenient material for making boxes.
When cardboard becomes damp, it will start to decompose or be eaten by worms. Every garden has a population of worms in it somewhere. Almost all the uses that cardboard may have in the garden, will ultimately end up with decomposition. But before it gets to that stage there are a few, limited, things that the structure of cardboard can be useful for.
You can plant things in soil that’s contained in a cardboard box. This can only be a temporary phase before they break down completely. The box and plants can be planted straight into the ground. The roots from plants will grow through wet cardboard. There is nothing bad about allowing cardboard to find its way into the soil structure. It won’t add anything to the soil structure because the worms will reduce it all to worm casts.
Can cardboard be used as mulch?
Cardboard can be used as a mulch but it may look a little unsightly if you use it in this way. It will work perfectly well by itself but you may need to make it wet or add some weight to stop the wind from blowing it around.
The only problem with using cardboard as a mulch is that it tends to be appetizing to worms. The structure of moist cardboard is ideal for worms to eat and unlike most materials that we mulch or compost, moist cardboard doesn’t need to go through the stages of going mouldy then rotting sufficiently to be attractive to worms.
To cover the cardboard that you want to use as a mulch, many people suggest that you could add a layer of leaf mould or lawn clippings. This would help if you don’t have enough cardboard to be able to have more than one layer. A layer of cardboard alone will suppress weeds very effectively for a short while.
If you add another layer of leaves on top, it will look better and do more for the mulching area. It will take longer for the worms to start eating leaves and lawn clippings because they will have to wait for it to rot. Cardboard as a mulch, can be eaten by worms from the moment it becomes damp.
Is it safe to use cardboard in a vegetable garden?
Cardboard is safe to use in the vegetable garden. There’s nothing in cardboard that’s in any way toxic. It can decompose and disappear into the soil. It will have no ill effects on the soil or threaten any of the vegetables that you want to grow.
It can be used in a number of ways. I’ve heard stories from people who have used a cardboard box to provide temporary shelter for delicate plants. They cut out the bottom of the box and place it over the plant. This has been found to be a useful way to protect plants like parsley.
Others have managed to shred cardboard enough to be able to place it around strawberry plants, although shredded paper is more preferable for this as it’s softer.
The best idea that I’ve found while looking into the subject is using cardboard when planting potatoes. This is to do with slug-control. If you are growing a line of potatoes in a vegetable patch, this normally involves digging a shallow trench.
The seed potatoes are planted in the trench. Then, if you’re unlucky, the slugs move in and either attack the seed potatoes or infest the developing crop.
Place strips of cardboard along the bottom of the trench and part-ways up the sides. Then plant the seed potatoes on top of the cardboard. Fold the cardboard in from the sides, cover with soil and water thoroughly. The cardboard will provide a solid barrier against any slugs for long enough to allow the potatoes to grow through the cardboard. The cardboard will be consumed by worms and disappear into the soil. It’s always good to get one over on the slugs.
Is cardboard ash good for soil?
Cardboard is, basically, wood ash. Everything about cardboard or wood ash is good for soil. There is a list of ingredients in wood ash that will make any experienced gardener smile.
The main part will be a calcium compound. Some will tell you that it will be calcium carbonate but, remember, we’re talking about ash here. Calcium carbonate that’s been subjected to heat, will degenerate to calcium oxide. This component needs to be handled with care. It would be wise to use rubber gloves if you’re handling a lot of wood ash.
When analysed, wood ash, typically shows a 25 to 45% inclusion of calcium oxide. The remainder will be other useful elements which include potash (about 10%), phosphates (about 1%) and a low level of metals including iron, zinc, manganese and copper. All of this will be good for the soil in any garden.