How should I use corrugated cardboard for mulch?

Question

I tend to have a lot of corrugated cardboard boxes laying around, due to getting various things shipped to my house. I have heard of using cardboard for a mulching material, but I'm not sure exactly how to do it (maybe I'm overthinking things). Ignoring the option of shredding and composting it:

Should I shred it and treat it like I would straw mulch? Should I rip it into sheets and just lay it down flat on the ground between rows? Should it be covered with anything, or can it just sit out? Is there some other method that I haven't thought of?

Answer 1

If you are trying to simply keep the weeds down, then I think some people do just lay it down flat. You will need stakes (eg. Bent metal pins) to keep them down and stop them blowing around. You could also cover the sheets with something more pleasing - wood chip mulch. The card would act as a barrier against weeds, and the whole lot will eventually break down.

Shredding would aid break down and composting. This is what I would do if I was putting the card in a compost bin/barrel (I put a lot of shredded paper in our barrel). it could also go in the bottom of a trench or pit, to aid water retention (actually this is what I'd do - early spring, till my raised beds and put the card in as low down as I can).

When composting paper and card, be sure to remove all the tape and any attached bits of plastic. Shouldn't be a problem with card boxes, but be wary of glossy inks - these can contain oils and metal-based dyes which might be problem (this problem is diminishing as more and more glossy papers and magazines switch to soya based inks).

Answer 2

I talked about my experience with cardboard as mulch in this answer:

I experimented this past summer by laying down overlapping sheets in the path between two beds in my vegetable garden and weighted it with rocks. It gave very good weed suppression. The only weed problem I had was that some creeping weeds would "hide" under the edges and sneak out the sides; it was harder to hoe these out since the cardboard was in the way. Don't do this if you care about appearance, it's a bit ugly.

Since weeds will poke up through gaps, and a single layer offers excellent weed suppression, I'd recommend against shredding or cutting the cardboard in any way. Just lay down big sheets and overlap the gaps.

Also, I'm going to guess that it's not going to do much for me this coming summer: I think it will be broken down enough that weeds will start to poke through, especially as it tears when I walk on it after everything thaws. I'll probably just put down another layer.

Answer 3

I used to use black plastic weed preventor but got tired of pulling it up when I rotated my vegs. Also it breaks down after a couple of years. One good thing about it though it allowed the water to seep through to the soil. I always covered it with pine needles as well.When I pulled it up in the Spring to move it there were a gazillion worms lying right under the plastic. This year I used corrugated cardboard and it worked like a charm as a weed preventor. I also covered this with pine needles.The problem is when I was pulling up my tomatoes this week(October)I noticed that the soil was dry as a chip and were no worms in sight !The only worms were the ones in the hole where I had planted the tomatoes. My conclusion is this, it works to great to prevent weeds but is a true moisture barrier to the soil beneath.Also it didn't look like it was even beginning to decompose after 6 months of being buried under the pine needles.