On Jan 8, 10:34 am, wrote:
On 7 Jan, 15:19, "Janice" wrote:
I am going to make some raised beds in my garden to grow vegetables as the
present soil is heavy clay. I already had a small raised bed made from 2ft
by 6in edging slabs and the difference in yeild was startling. I imagine
lengths 8in by 2in timber would be ok so what would be the best and
prefeably cheap timber to use? And what should it be treated with?
Jan
Use CCA [Copper Chrome Arsenic] (sorry its not called that any more)
Tanalth but make sure you get the timbers the size you want either by
special request or using standard sizes for your bed
Don not cut it! do not nail it but bind it in other ways or use copper
nails on stainless strapping
Matty is not correct in that the 'A' is no longer allowed and the
heavy metal ions are chemically fixed to the hydroxyl groups and
cannot leach out - that is the idea!
That is why it is OK for kiddies playgrounds
The only removal is by fungi translocating and you are not likel to
get that in you carrots!
Some people disagree that CCA is OK for gardens and playgrounds. In
fact many countries ban CCA timber in playgrounds. If there is a non-
CCA alternative I'd use that instead.
http://www.garden-nz.co.nz/forum/30153.html
"Tanalised, pressure treated or CCA timber are all terms for a wood
preservative system based on copper, chrome and arsenic. For years we
at HDRA have advised our members not to use tanalised timber to edge
vegetable beds and make compost boxes, simply because we felt that the
chrome, a toxic heavy metal, and arsenic, a poison used in the
preservative had no place in an organic garden
These worries were confirmed in spring 1997 by alarming reports from
the USA. Researchers found that decks made from tanalised timber can
leach high amounts of arsenic into nearby soil. Samples taken from
beneath treated decking contained up to 80 times more arsenic than
surrounding soil and as much as 35 times the legal limit for arsenic
in the soil. The study found that arsenic leaches quickly from treated
wood..."