Raised Vegetable beds - Knowledgebase Question

Jackson, Mi
Question by lwolff1962
March 3, 2011
I sent a question in b4 & never rec'd an answer.
Building raised veggie beds can we use treated lumber if we line the inside with tarpaper? How much top soil over fill dirt do we need?

Answer from NGA
March 3, 2011


Sorry you did not receive the answer to your question. I remember answering it so the email either got lost in cyberspace or ended up in your junk mail box. Here's the original answer:
There are two sides to the story concerning the safety of pressure treated wood in gardens. One says such products are safe, and cites studies showing little or no leaching of arsenate for years. The other side has it's own studies and says heavy metals and toxins do leach at dangerous levels. So, I err on the cautious side and recommend gardeners not use pressure-treated wood, especially for food plants. Try cedar, redwood, hemlock, plastic wood or cement blocks as alternatives. If you already have the wood and want to use it, line the inside of the planter with plastic to reduce the risk of the chemicals leaching into the soil, then fill with the topsoil of your choice. I'd go a step further and not plant root vegetables such as carrots, potatoes or radishes close to the edges of the beds. Above-ground veggies should be just fine. So as not to waste space, I plant sturdy annuals such as marigolds along the edges of my raised beds - it's attractive and will sometimes keep insects at bay. You'll need at least 18 inches of soil to provide adequate root room for your veggies. Fill the bed and mix your top soil over the fill dirt so the depth is at least 18 inches. Hope you have a bountiful harvest!

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