This question asks about using corrugated cardboard for mulch. In the comments and the answer there are some questions about glues and inks possibly having "bad stuff" that you might not want in the vegetable garden.

I'm wondering about cereal boxes (this type of cardboard in general). They're printed with glossy inks, which from what I read probably have heavy metals? Does anyone know of literature about what's in these boxes/inks and whether it would be safe for mulching around vegetables?

2 Answers 2


Cereal boxes have been in the news recently, in Europe. According to the latest research, they may leak harmful mineral oils into the foods they contain - oils which originate mainly from the ink in the recycled newspapers that are used to make them and, to a lesser extent, from the printing ink on the box, and may be carcinogenic.

As yet, there is no hard evidence that these mineral oil hydrocarbons that migrate into our foodstuffs are a health hazard ; and even if they are, those that are present in the cardboard might well be converted into harmless substances on contact with the soil, over time. However, given the potential risk, I would definitely avoid introducing them into the food chain by using cereal boxes either as a mulch or a composting material.

There is a very full article about the issue by the UK National Health Service here

  • Thanks for the link. I had seen this issue mentioned in my research but hadn't seen that NHS article which will provide ample fodder for further research...
    – bstpierre
    Jun 30, 2011 at 21:11

I take it you are referring to using cereal boxes as a weed barrier, instead of using some kind of landscape fabric, that you will then cover with some sort of mulch material, e.g. a 50mm/2 inch covering of compost.

If yes to the above (in fact regardless of your answer to the above), I personally wouldn't recommend using any kind of colour/treated cardboard or glossy paper or colour printed paper as a weed barrier.

Why? As such materials are broken down the chemicals used in the original process will leach back into the surrounding soil. Therefore without scientific research and time to see the possible long term effects, why run the risk of any potential problems in the first place...

Generally accepted non landscape fabric web barriers are plain (black & white) newspaper (2 or 3 layer thick) and plain, untreated brown cardboard.

For a lot! of mulching information, take a look at Gardens Alive answers beginning with "M".

  • @Mike: Welcome to the site! Thanks for your answer. To your question: yes, something like that. Possibly also as a component underlaid in paths as a weed barrier. To your answer: I've heard this information before, but never with a reference to something authoritative about the problem with printed cardboard. I'd like to read and understand the science involved so that I can make a decision about whether to use and how to use these materials.
    – bstpierre
    Jun 30, 2011 at 18:47
  • @bstpierre - Unfortunately I don't know the real science behind it, the little I do know is, it is related to the breakdown of the material & the chemicals used in the original process leaching back into the surrounding soil (that can cause problems).
    – Mike Perry
    Jun 30, 2011 at 19:04
  • Colored paper/card is less of a problem than it used to be due to the move towards soya-based inks and less use of metal-based pigments. However, you still want to keep away from many of the treated and coated cardboards - e.g. sealed juice cartons. Those plastic coatings do not break down in a horticultural timescale.
    – winwaed
    Jun 30, 2011 at 19:04
  • @win - Indeed, I use the cardboard milk/juice cartons as seedling containers precisely because they seem to never break down.
    – bstpierre
    Jun 30, 2011 at 19:07

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