One is good enough. The plural of box may be used because of area: I don't have a single box that would cover a reasonable garden bed area by itself. (well, the box that my flatscreen came in, but the bunnies hang out in it).

If you have extra cardboard- then use it as a second layer... just to get rid of the cardboard, not because it's needed.

A lot also depends on your climate. The higher the humidity, rain, etc. the quicker the layers break down.. In our dry climate, a couple pages of newspaper is sufficient.

Maybe you could call a furniture store and ask if they get boxes on mattresses or refrigerators. That would cover a lot of ground--quick.

ItÂs been my experience that corrugated cardboard does not last as long as multi-layers of newspaper (about 10-15). Even two layers of corrugated cardboard will barely get you thru one season. So in a vegetable garden it would work fine. In a perennial garden newspaper seems to work betterÂfor me anyway.

Maybe I didnt say it in a sensible way...I was thinking that I would cut the boxes open and lay the cardboard out flat which would be a single layer on the ground... but then when I thought about the word "flattened" ... well my boxes are already flattened ... which is double layers.(like front and back) Should I leave them in flattened double thick form instead of cutting them open and laying out a single layer?

Glenna,

I would say go with the "flattened", double layers, not cut opened into a single layer box.

1 "layer" (a box cut opened and laid out to a single layer) will not last the season, I made that mistake last year. I am in PA and it is humid and damp here, if you are in Ohio you will have the same conditions.
So, if you have enough cardboard to cover everything without cutting up the boxes and spreading them out in 1 layer, do that.

I have a side question about using cardboard. I have a bed that is overrun with weeds and have been thinking of using cardboard to smother them, but there are shrubs planted in the bed and I was wondering if rain will penetrate or will the shrubs die of thirst?

I think it depends on the thickness of the cardboard. If you are using say appliance boxes that are 1/4" thick, go with one layer. If you are using uncorrugated cardboard go with more. I don't think you can over do it. If you need more cardboard, stop at an appliance or furniture store. I grabbed over 60 refrigerator boxes for my beds. Could have had twice that many if I wanted! I did go double thick around the edges, since I did not use any edging material like bricks, or plastic edging etc.

One layer of cardboard is sufficient. How long that will last on your soil depends on how healthy your soil is. But most all "weeds" should be dead in about 6 to 8 weeks, although very aggressive "weeds" may not succumb even in two or three years. There should be no reason to need newspaper or cardboard that lasts more than one growing season.

Kimmsr, I hope you are right as I am almost finished with my first and large project using cardboard and I only used one layer. I will be so disgusted if all the grass and weeds come back!

Thanks to all for the feedback. I went ahead and used 2 layers for this small veggie patch just to be on the safe side.
timshaw... I already built a small bed around some existing plants about 3 or 4 weeks ago. (only 1 layer of cardboard) I put some bulbs in it yesterday and the cardboard was soggy... I think that the existing plants should be fine. All of the layers of material and the card board should absorb and hold lots of moisture. but that was my first bed so I cant swear to this yet. haha