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Is Treated Wood Safe for a Vegetable Garden?

Cedar Fencing
Nothing lasts forever, not even cedar fencing or decking materials. No matter how many times you reseal and re-stain, that cedar fence or deck will eventually succumb to the elements. Fortunately, there are plenty of ways to reuse old fencing and decking materials. One of the most popular applications is to turn old fences and decks into raised vegetable garden beds.

If you’re eco-friendly enough to prioritize reusing rather than simply trashing old fencing and decking materials, you’re probably also earth-smart enough to recognize the potential hazard of using pressure treated wood in food production. Pressure treated wood is created in a tank; the air is vacuumed out, and then preservative chemicals are added in a highly pressurized setting. Because there is no air barring their way, these chemicals go deep into the wood pulp, thereby extending its durability.

Pressure Treated Wood in Fencing and Decking

Cedar fencing and decking professionals rely on pressure treated wood to stand up to soil moisture. Pressure treated wood is preferred for posts and framing materials that will be in direct contact with the earth. Non-treated wood quickly rots in these conditions, especially in moisture-prone areas like the Pacific Northwest. Rick’s achieves excellent stability and durability in our cedar decking and fencing by using pressure-treated wood for posts and framing materials.

Potential Hazards of Pressure Treated Wood in Vegetable Gardens

A little less than a decade ago, chromated copper arsenate (CCA) was the preferred chemical bath for treating wood. Copper was chosen because it prevents fungal growth. A form of arsenic called arsenate was used for its insecticide properties, and chromium was needed to bind the chemicals to the wood pulp.

However, in 2003 the US wood industry voluntarily stopped using CCA, in agreement with the EPA. Given that arsenate and other forms of arsenic are carcinogenic, older pressure treated wood should be handled with care. If you decide to use CCA pressure treated wood in vegetable beds, it’s wise to line each bed with an impervious material such as plastic. That way the chemicals can’t leech into the soil, and your veggies and fruits won’t be tainted.

However, modern pressure treated wood is primarily treated with copper azole, which is safe for food applications. Copper is often used to amend soil, and azole is also used in food growing operations. Both ingredients are harmless for vegetables and fruit; if you grow food in copper azole pressure treated beds, your family will be safe.

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