[Matt Whalley]

I'm new to this veg growing game but for a first go in the second half of the growing season I've done pretty well with carrots, spring onionsm tomatoes and loads of salad leaves.  I'm a bit limited for gorwing space and so I'm going to create some raised beds to more than double the space I have to grow in.  

I was going to use tanalised timber deck joists (for there weather resistant properties) to create the "walls" but the thought has just crossed my mind as to whether that's safe.  Will whatever they treat the boards with leech into the soil and contaminate the veggies I will grow in there, thus making them unsafe to eat ??  I really don't know now if this is such a good idea.  Can any one give me an idea if this has been done before or if in fact there is something that would do the job of building the structure without the potential harmful effects ??  I've also considered sleepers but there thickness means I will loose quite a bit of growing space and I'm not sure if there is the same contamination issue with them.

Any help greatly appreciated

Confused of Kingswinford   :?

[Matt Whalley]

I think I may have answered my own question with a little further research, apparently the cheicals they use to "tanalise" timber - or also if it called pressure treated timber - include compounds of arsenic, chromium and copper.  Back to the drawing board.

http://files.recycleworks.co.uk/files/Wood%20preservatives.pdf

this is the piece I have been reading, makes for some enlightened thinking re the decking I was going to do !! :shock:

[richyrich7]

Hi Matt welcome to the forums I've not read the link yet but we have grown veg in raised  beds made from tanalised decking boards for about 4 yrs or so and felt no ill effects..
However you could make them out of concrete gravel boards instead if you feel worried about the use of tanalised timber.

[Matt Whalley]

Richyrich

Thanks for the info.  I ran it by my folks who are both a bit green fingered, although they don't eat anything they grow as it's all for show ! - and my mom suggested lining the boards with something like a pond liner or butyl rubber.  This solves both the problems of the potential effects of tanalised timber and the problem of using untreated timber that will rot eventually.  The only concern is, as I was going to do, if you use the ground below the level of the bed to grow into ie carrots parsnips etc,  and consequently the level of the wood,  is the leeching from the boards into the ground below them that the lining of the structure just wouldn't prevent.

We've got a pretty good timber merchant not far from us so I'm heading down there this afternoon to see what they think.

As for the link, I hope it doesn't alarm you to much.  The info it gives relates to the leeching of arsenic from the wood into the surrounding soil, that's the bit that causes me most concern.  The comment regarding the levels of arsenic found in soil under a decked area compared to that found nearby is pretty concerning.  

Matt

[Riala]

Just don't forget holes in the bottom for drainage.

[richyrich7]

As for the link, I hope it doesn't alarm you to much.  The info it gives relates to the leeching of arsenic from the wood into the surrounding soil, that's the bit that causes me most concern.  The comment regarding the levels of arsenic found in soil under a decked area compared to that found nearby is pretty concerning.  

Matt

No it doesn't worry me too much Matt, it is a concern however when you think of the number of play equipment that is made from tanalised timber.

But I don't think it said what levels are absorbed by the plant that's the bit you eat not the soil   so if a plants not absorbing it is there any real worry ?

[Matt Whalley]

Richyrich

You've hit on exactly the bit that is making it hard for me to decide the way to go, does the plant actually absorb it ??

I spoke to the timber merchant and he was none the wiser as whether it would cause a problem, but as he said he's not a gardener he sells decking and fences !!

I've priced it up using untreated wood and it's going to be pretty economical, and the guy in B&Q reckoned you could treat the outside with Linseed oil which would give it some protection.  I reckon this is the winner.

[richyrich7]

You could probably treat the inside with linseed oil as well.  

I'd like to see some evidence 1st about plant absorption of poisons before I get to bothered to be honest. It seems that a lot of half baked claims are made about lots of things esp the environment band wagon.

But you have to do what makes you feel happy with