Wednesday, 8 January 2014

Is it safe to grow veggies in Styrofoam boxes?

I know that many gardeners around Australia and possibly elsewhere in the world, grow vegetables in Styrofoam boxes especially if they are renting or don't have a lot of space to put in larger gardens. We recently saw a couple of episodes on the ABC's Gardening Australia where the boxes were made into self-watering containers. As it is very dry here in SE Queensland at the moment and we are always on the look-out for any gardening methods that will save us water, we bought some broccoli boxes from a local greengrocer to give it a try.

We were quite interested to see on  Gardening Australia recently that a young couple living in rental accommodation were growing heaps of vegetables in Styrofoam broccoli boxes. The programme was called A Small Kingdom. In an episode later on in the year, Jerry Coleby-Williams showed viewers how to make a self-watering container also using a broccoli box.

My husband, being a tad deaf, thought that Jerry said you could use either gravel or Styrofoam (he really said pearlite) in the base of the Styrofoam box so had a scout around the back yard for old Styrofoam boxes and I was given the job of breaking them into pieces to put in the base. However, I got tired of doing that so finished off filling the water reservoir section with some of the leftover cypress chips from our watersaver garden.

A hose had already been placed in the bottom of the box to deliver water as needed once the box had been set up.

A drainage hole was cut into the side and then water was added to the base and filled until it reached the drainage hole.

As this was purely an experiment with different materials, the gardening CEO decided to then cover the base with weedmat whereas Jerry used shadecloth to hold the soil. Then the homemade potting mix was added. I had some beetroot seedlings which really needed to be planted out and, although they probably aren't the best plants to use in this system which is ideal for leafy vegetables,we wanted to see how they would cope with the extreme heat during the forecast heatwave.

So just before the heat hit I planted a few beetroot seedlings last Thursday the 2nd January...

and they survived the record breaking heat during Saturday when it nearly reached 40 degrees here. I took this photo yesterday, 7th January, and they still looked quite healthy.

The CEO decided then that he would make another large watersaver garden as someone had offered him the base and that he would use Styrofoam pieces in the water reservoir which would make it cheaper than buying more cypress woodchips so he has been collecting more Styrofoam. I told him that Jerry had said Pearlite on the show not Styrofoam so he said to check it out so I clarified that issue after watching the Gardening Australia programme again.

While still on the computer, I thought I would do some searches to see what other people used in their water reservoir if they were using the same type of boxes and suddenly I remembered that it is always a 'no no' to drink hot drinks out of Styrofoam cups so started searching about whether it was actually safe to grow food in this product at all.

Firstly, I read on the ABC message board that it was probably safe to use it.  Then a search on the safety of Styrofoam came up with a search result which linked to the US breast cancer website which was a bit unsettling to say the least although there was some good information about plastics as well.
This website was a bit confusing as it sounded like it was okay to use it for growing plants but then someone in the comments section says it is definitely not safe to use when growing vegetables. Then the CrossRoads website says this:

 Styrene is classified as a possible human carcinogen by the EPA and by the International Agency for Research on Cancer (IARC). 
I would rather err on the side of caution but was wondering if anyone reading this has looked into the safety of growing food in Styrofoam boxes. I know you can't believe everything you read on the internet but I wouldn't even know where to go to find out the real facts.
Can any of my readers enlighten me or am I just being paranoid? :-)

16/4/14 If you would like to read more about this issue there is an updated post here.



  1. Good question Nanna Chel. Sorry I cant answer it though. As I was watering my potted herbs this morning, I started to think about the plastic pots they are in. The are probably no good either. I will be interested to see if anyone knows about the foam boxes :)

  2. Yes Tania, it does get you thinking. I was wondering about the plastic pots too and then there is the black plastic used in the base of wicking beds. I think I have opened up a can of worms for myself :-)

  3. I wrote a long spiel in reply to this an hour or two ago but it wasn't accepted. Maybe too long? I'll try rewrite parts of it later and come back then!

  4. Thanks Ree. Not sure how much you can add in a comment box. Do you want to email your reply and I will add it to the post?

  5. I am in the dark too. I guess what we buy is stored in these containers for weeks at a time but it does not mean they are safe. I have been wanting to make some of these but our neighbourhood garden seems to get all the boxes :) It's on my to do list which is getting rather lengthy!

  6. I think it can may be safe but I am not pretty sure as I have not tried it ever . But I will try in futute this type of experiment and according to me styrofoam boxes will definitely help in growing these.

  7. I'm not sure I've not heard anything and I am pretty paranoid about heath at the best of times. I actually grow all my seedlings in Styrofoam boxes but then replant into the garden, I more use mine at a hothouse with the glass sheets on the top. Sorry not much help.

  8. The issue with Styrofoam is extreme heat. Small containers subjected to extreme heat are a problem, whereas large containers that stay reasonably cool are quite safe. this explains why a hot drink in a small container is quite different to a large box full of cool water and earth. I hope this helps the conundrum.

  9. Thanks Phil. I will keep that in mind.

  10. Thanks for the great article and raising the issue. I'm about to create a massive, irrigated garden in my back yard using the styrene boxes. I'm cautious, though from what I've read online, Phil Pogson is right. It depends on extreme heat and volume of container.

  11. A good mineral to add to the soil then would be selenium as that has been proven very effective against cancer. There is a really good youtube video here:

  12. They are toxic. See what happens when you burn them. Any plant you eat isnt safe. As someone that grew up on a farm and uses these boxes only as storage for produce to ship out. As a country fire member, I have seen how toxic they are. I have a firm belief what is in the foam will leak out into the soil and food. How much is the question you are asking. Need to test it after and see if there is a difference in toxics before and after a while. However, my motto is, if its a slight risk, do not use it. What most people dont do, is test their soil before hand for bad chemicals. If you are using your dirt as well as potting mix, you should get it tested.

  13. I was thinking of using styrofoam as my medium for growing herbs hydroponically and that's how I found this sight...wanting to know about food safety. Then I read all comments and thought, well gee...people pour boiling beverages and microwave food in styrofoam and eat drink it, I don't, I'm not a fan of plastic and glass is widely recyclable so anyway it doesn't seem it would be that bad with tepid water but I think I'll transfer them to clay marbles when they get s good stalk. Thanks all:)

  14. "Although some chemicals in the foam can leach out if it gets overheated -- such as when you heat a foam cup of coffee in the microwave -- it doesn't leach chemicals under normal temperature circumstances, according to Dr. Andrew Weil, a pioneer in the field of integrative medicine. The soil in the container -- and therefore the foam under the soil -- doesn't get hot enough to cause a problem since it normally stays cooler than the ambient temperature." -


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