Should we use treated pine as a border?

We are building a veggie patch and wonder about using treated pine as the borders. Is it toxic or environmentally friendly?

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7 answers

Pine is treated to prevent rotting, insect and borers. It lasts much longer outdoors than untreated pine.

However, old style CCA treated pine (Copper Chrome Arsenate) contains arsenic, which can leach into the soil. Especially when used in play equipment and outdoor furniture, it has been linked to health risks like cancer. It also can leach into the soil and be absorbed by plants – definitely not ideal, especially if you plan to eat those plants. And isn’t the point of growing your own food to control the chemicals in it?

From 2006, CCA treated pine is no longer used in schools or decking, outdoor furniture, play equipment, handrails etc. This was announced as a precaution. Apparently for normal individuals, there is a pretty low risk. Though if you are pregnant, elderly, immuno-compromised or have children, I’d avoid it. We are also all exposed to a small amount of naturally occurring arsenic in food, and our bodies do seem to tolerate it.

Personally, I would use untreated hardwood sleepers. Hardwood gets an H3 durability rating – just the same as CCA treated pine. Some hardwood even gets an H4 rating. So why risk exposure to toxic chemicals?

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Whatever wood you choose, make sure it is from a responsibly managed forest. FSC (Forest Stewardship Council) certification guarantees this.

Treated pine often comes from a plantation, which is more sustainable than old growth hardwood timber. But then there’s the toxic preservation problem.

New Redgum landscaping sleepers might seem like a good idea – they are quite durable and not treated. However, Redgum is an Australian hardwood that is under threat from logging and environmental degradation. I wouldn’t touch it.

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In some ways, timber preservation is a good idea – it means the timber we use lasts longer. But any benefits of chemicals used in preservation must be balanced against their environmental impact.

If you really want to use treated pine, newer ACQ pine is arsenic-free. ACQ stands for Copper, Quarternary and Ammonium Compound. It resists similar pests and fungus to CCA treatment and functions exactly the same. It looks greenish when new, like CCA treated pine, and fades over time. It is often not stocked by retailers like Bunnings or timber yards, but you can usually order it in.

You might like to look into alternative wood preservatives, like Eco Wood. It uses a different preservation method. However, the product information recommends avoiding direct contact with food and drink, though it claims it can be used safely to stake tomatoes, etc. I don’t know if I would use it in my veggie patch…

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Instead of wood, why not use recycled bricks or stones? Or salvaged railway sleepers?

You could also use plants as a border – try rosemary or curry plants. Then you avoid the problems of timber sustainability and toxic chemicals altogether.

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Cypress Pine logs are a good idea as they are naturally termite resistant. Untreated native hardwood might be a great choice too. Ironbarks are especially hardy. Most hardwood IS sustainably harvested in Australia. Selectively logged native forests, preserve a natural ecosystem and support diverse wildlife. Contrast that with the exotic pine plantations that were usually established by clearing coastal forests and are biological deserts.

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I wouldn't use them anywhere need food that you grow for consumption. In fact I would never use anything so toxic - after living through the bushfires in February 2009 there were so many treated pine posts burnt and toxic green dust everywhere. I hate to think of the effect that this had as it would have ended up in local air and water cycle systems. There are plenty of other options just go free shopping on hard waste day and you will get all sorts of non-toxic materials to build garden beds and fences.

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its beta 2 use woods with high extractive content that can offer natural durability 2 avoid use of preservatives which are risky 2 human health and non environmental friendly.

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