Are grow boxes made from treated pine safe for plants?

ozzy

I've made some training boxes from pine treated with copper chrome arsenate, do you think they'll be safe for use with Bonsai?.

My local Bonsai shop owner says she's had plants growing in treated pine training boxes for years without any problems, does anyone else have any experience in the use of treated pine grow boxes.
Correct me if I'm wrong but aren't copper and chrome trace elemants anyway, and I've done some basic research on arsenate and I've found its actually quite a common element in garden soil.
What are your thoughts on this?

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Joanie

Can't help you with your basic question, but from the picture it looks like the wooden bottom slats are too close together. If you leave a little gap and cover it with mesh, you will have excellent drainage, which is one of the best points about using growing boxes.
Joanie

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ray hernandez

Hi, Ozzy- I have several nursery containers that were treated w/copper chrome arsenate on the inside. they're supposed to keep the roots from circling in the pot kind of self pruning the feeder roots. So far so good, its been six months since I've using them-I'll let you know how they work out. As for the grow boxes I don't see any reason why they wouldn't work the same way. Ray

Alasdair

Having an understanding of chemistry and knowing how poisonous copper and arsenic can be i would steer well clear of this treated wood. In the short term it may have little effect on your trees but over extended periods (years) it may slowly build up and poison your tree. I found some info on it here which mentions up to 13% of the chemical leaching into the soil and binding with it. In the small amount of soil held in your box, this could be a worry.

Al

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ElGringo

Copper, chromium and arsenic are pretty poisenous to plants. They don't possess cytochrome enzymes and metallalothioneins that we do that help us detoxify poisenous stuff in our bodies.

Toxic metals compound sorb (temporarily stick to) soil particles, especially fine, silty organic particles like clay. Clay only looks red, because it has so much iron oxide stuck to it. If the soil in your box was really gritty, then the toxic componds in the pine would have nothing to sorb to, and would be flushed out each time you water. When they stick to soil particles near to a root, there is a chance that they can be absorbed by the tree of course.

I have a crazy idea! Put charcoal around the inside of the box. Any toxic metal compounds that leach from the pine will preferentially sorb to the charcoal and not the soil. As long as the trees roots don't infiltrate the charcoal, it should be ok.

But, if you're really concerned, plastic pond baskets are safer (but not as robust). But you know that already!

What do you think Alistair? I have a biological background really, not so much chemistry.

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Richard


If I was a lady, would I be 'LaGringa'?

ozzy

Thanks for the replies ...

Joanie ... I made some boxes last year out of old pallets and did like you said and left plenty of gap with mesh covering the holes but no matter how much I watered the water just seemed to pour out everywhere, not just out of the drain holes but out of all the seams too and leave dry areas in the soil, this time I have hardly any gaps at all and the water takes a while to drain out but seems to wet out the soil better, I'll see how it go's, if need be I'll drill some more holes in the bottom.


Alasdair ... I would have thought any chemicals leaching into the soil would be easily flushed out but as you have said it appears that the chemicals can actually bind to and hang on to the soil.

El Gringo ... I do tend to use coarse gritty mix so this could be beneficial in flushing as you suggested.

I also just noticed an interesting post by matt down below in the Similiar threads list about grow boxes thats very interesting ... http://forum.bonsaitalk.com/showthread.php?t=1803

Graydon

CCA treatment is to control insect infestation primarily termites and carpenter ants. I have read lots of stuff by manufacturers stating it's fine for plants and people. Then I saw a local (to me) story where a playground had to be closed because of ultra high levels of arsenic in the soil leeching from the PT wood from the structures. If the manufacturer thinks it is safe than perhaps they wouldn't mind eating all of their food from CCA treated wooden plates. Remember this is a chemical combination designed to KILL THINGS. CCA does not prevent rot.

Why don't you use regular (non treated) pine? It is cheaper, less toxic and just as available and the splinters do not hurt nearly as much.

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Alasdair

I would still be cautious though. Treated wood around crops in the ground is very different to growing a bonsai in a box for lets say 3 years. Amny crops grow for opnly one season before the whole plant is ripped up and replaced next year, giving only a few months of exposure.

Something else which has just sprung to mind: how might the CCA react with fertiliser? The arsenate group is very similar to phosphate and they may substitute each other.

Personally i would not expose my trees to this treatment, but thats my opinion. I think the arsenic in particular causes enough concern.

ElGringo, I'm rather familiar with biology too (going to study plant biology at university next month). What you said is correct, but the arsenate would also adsorb onto the plant roots and intefere with the phospholipid bilayer around each cell.

I'd steer clear.

Al

edit: in the link i posted before (only just noticed) that a spoon full of ash from CCA treated wood is a toxic dose for a human. That can't be good.

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I can feel another "I wish that was my tree" moment coming on...
Currently studying BSc Plant Biology at the Universty of Wales, Aberystwyth

ozzy

I guess the safest thing to do would be to just line the box with a plastic liner, I have managed to find some more information on treated pine and some of it makes very interesting reading, particularly the animal and vegetable tests.

See the sections

The arsenic in CCA
Leaching

in the following scientific report ... http://www.ffp.csiro.au/TI-CCAFactSheet.asp