[Scottish Mike]

This IS a noob question, but I am one! Also, I haven't had much luck at finding a consensus online, so I thought I'd just ask:

Developing our plot has reached a bit of a standstill as I've realised it's time to get the raised beds constructed. Having looked around here and on other sites, the advice is for raised beds to avoid certain types of treated wood as this can damage the soil.

Are planks of timber from Wickes/B&Q/Homebase appropriate? Treated with something like cuprinol? What sort of treatment is alright/safe to use and what sort should be avoided?

Any advice would be great thanks

[surbie100]

I use decking from Wickes. It's treated with Tanalith-E and is supposed to be ok for growing veg:

TANALISED E pressure treated timber is suitable for the construction of compost bins and for use as earth retaining structures for organic vegetable beds. The Soil Association (www.soilassociation.org (link is external)) states that if the timber used for organic vegetable beds is preservative pre-treated then there are no issues in terms of organic status. If, however, the wood is treated once the raised bed has been built (brush applied preservative) then this would affect the status of the land.

I have painted them with shed paint to increase the waterproofing, and where the bed is not in use over winter I pile the soil away from contact with the boards. My possibly feeble reasoning is that it will stop the boards being so wet (my plot is very very claggy) and keep them from rotting as quickly.

[Kristen]

I've put damp proof membrane (pond liner would be an alternative) on the inside face of my planks - to reduce the contact with the earth, to prevent leach of potentially unpleasant chemicals into soil/crops, and to make the boards last longer.

Dunno if the plasticisers in the sheeting are more of a threat than the tanalised wood preservatives though

[surbie100]

Dunno either Kristen. 

Mine have heavy-duty mypex fixed half-way down with clout nails. This goes under the board, lines the path and is fixed again to the neighbouring bed. Wood chip on top. Again, it's to cut down on plot weeding/mowing, which I just don't have time for.

[Kristen]

I plant all my veg plants THROUGH Mypex too ... more plasticisers being absorbed into the food to worry about ...

Would that be allowed for organic growing / by Soil Association I wonder?

[Annen]

I use untreated (by me) scaffolding boards and, if I remember, I do what Surbie does and pull the soil away from the boards through the off season.
I don't know how long they last, but it is much less trouble and worry than treating or lining and I am all for less worrying 

[Kristen]

it is much less trouble and worry than treating or lining

I thought about the using scaffolding boards, they seem cheap to buy (if you can find a source locally-ish), but the effort of building the beds - soil to the middle, and upright support pegs, and get it all fairly level - was quite significant for me - numerous days, rather than a few hours, and I made my choice based on not having to do that again any time soon!

[mumofstig]

I plant all my veg plants THROUGH Mypex too ... more plasticisers being absorbed into the food to worry about ...

Would that be allowed for organic growing / by Soil Association I wonder?

According to garden organic organic gardeners do use them

. Black polyethylene mulches are widely used for weed control in organic and conventional systems in the UK

http://old.gardenorganic.org.uk/organicweeds/weed_management/show_wman.php?id=18

[Annen]

it is much less trouble and worry than treating or lining

I thought about the using scaffolding boards, they seem cheap to buy (if you can find a source locally-ish), but the effort of building the beds - soil to the middle, and upright support pegs, and get it all fairly level - was quite significant for me - numerous days, rather than a few hours, and I made my choice based on not having to do that again any time soon!

I'm not very handy at the DIY stuff, but all I did was drill three holes about an inch from the end of one plank then butt the end of another plank to it and hammer some 4/6 inch mails through the drilled holes. They have only been in 2 years but as long as you don't do anything silly like lever it with a spade they should stay together okay.  At least that is what I am hoping. As for filling them, I manoevred them into position ( another pair of hands is useful here) levelled them as best I could and dug out a path around them, throwing the soil into the bed. They were only half full so one at a time I did the lasagne bed thing and with the addition of a load of council soil improver, they are nearly all full.

A word of warning about scaffolding planks though, they seem to be a disappearing resource, as more scaffolding companies seem to have gone over to metal staging.  Our allotments planks for sale have gone from £3 to £7 per plank with no profit, and we are finding it hard to source any more.

[LotuSeed]

I used pressure treated decking boards for all of my raised beds. PT lumber used to be (and I believe still is in some parts of the world)  treated with Chromated Copper Arsenate (CCQ), which some believe to pose a health hazard. Nowadays, PT lumber is treated with a water based wood preservative called Alkaline Copper Quaternary (ACQ), which doesn't carry the potential hazards of the arsenic-containing CCQ lumber. Prevalence and availability, I'd imagine, will vary from region to region. All of the pressure treated lumber I use for raised beds is marked ACQ and is sold under the brand "Yellawood".

For more reading
http://en.m.wikipedia.org/wiki/Chromated_copper_arsenate