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Treated Timber

Natural timber is best

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Should organic gardeners use treated timber when building structures in the garden? JUSTIN RUSSELL shares his experience.

It’s confession time. When I built my vegie patch seven years ago, I made the raised beds from CCA treated pine. It wasn’t a spur of the moment decision. I did lots of research before splashing out on a big pile of sleepers. My decision was based mostly on research done by the CSIRO, which suggests that while it is possible for chemicals to leach from treated timber, the amounts are likely to be minute, and there’s a very low risk of vegies becoming contaminated.

In hindsight, I wish I’d opted for good old, untreated hardwood. Not so much because I’m worried about the health risk, but for a range of other reasons. For one, I thought the treated sleepers were a bargain at just $11 a pop for 200mm by 50mm by 2.4m units. In reality, the sleepers were unseasoned, warped badly in places and despite longevity claims by the manufacturer, some have already started to rot. Untreated hardwood used in other parts of the garden is still going strong after being installed 30 years ago.

Second, I try to make a point of following the guidelines laid out in the Australian Organic Standard, the document that lists all the inputs that are allowable on certified organic properties and those that aren’t. While I haven’t yet applied for certification, I’m considering doing so in the future and under the standard, treated timber is most definitely, out.

My third dilemma is that if I now want to replace the treated pine with hardwood, there’s an issue of disposal. Treated timber can’t be burned, so it would have to be dumped in a landfill. That’s a serious waste of resources as far as I’m concerned, so for now, the treated stuff will remain in the garden.

Contrary to popular belief, CCA timber hasn’t been banned. It’s been restricted for use in some applications, and is still available to purchase at your local hardware store. Other preservative options are available, but they are still based on toxic chemicals and therefore not allowed under the organic standard.

To be honest, I regret my decision to use treated timber, and I’ve learnt from my mistake. I now use untreated recycled timber wherever possible, and if I have to buy timber for an outdoor project, untreated hardwood fits the bill perfectly. I’d encourage you to do something similar.