Q. Dear Umbra,

I am constructing a garden bed for a local preschool and am considering the various materials I could use. The beds need to be raised and protected by a rigid border. This has aroused two main concerns: the safety of the children and the durability of the materials. I feel the best long-term way to keep large splinters out of tiny hands would be to use the plastic/wood composite decking. However, I have reservations about the volatility of the material, though the EPA report says it is safe. I have read that the Polyolefins in the composite are mostly inert, but am concerned, as the garden may be used for vegetables. Have you any related information?

Thanks a bunch,
Richard G.
North Carolina

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A. Dearest Richard,

I’m a big fan of wood for raised beds, and part of me wants to reassure you that there are ways to get around splinters. If you purchased planks that were slightly finished, for instance, it would be more expensive than rough planks, but the splinter index would go down. Also, kids can learn to handle garden tools without beaning their friends, so surely they can learn to be near wood without getting endless splinters.

My reasons for preferring wood are hardly scientific. Children are learning to touch the soil and raise plants, and for me that experience should be mediated through a natural material. Which one? Well, cedar is long lasting but expensive, pine is cheap and first to rot. Whatever wood you chose, the beds would not last quite as long as the fake wood. But I personally dislike the texture of plastic lumber — I don’t find it welcoming. If you think this aesthetic revulsion sounds crazy, then perhaps it is only my pet peeve.

My little anti-plastic moment aside, the wood-plastic composite “lumber” does appear to get good marks from all the resources I checked with: extension offices, state governments, safe playground advocacy groups, agriculture advisors. The plastics used (often HDPE, or recycled materials) are apparently non-leaching. They are solid, long-lasting, and easy to work with.

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A couple of other notes for all ye out there building raised beds for any purpose: do not use wood treated with Chromated Copper Arsenate (you shouldn’t have access to buying it new anyway). Although there are treated lumber products on the market that do not contain arsenic and are less toxic, I would also eschew these. The newer preservatives are understood to be less toxic, but I say why risk it. Also, avoid railroad ties, which may have been treated with creosote.

Other than plastic lumber and wood, good materials for raised beds include cement blocks and broken sidewalk pieces, which you would get from your public works department, not from jackhammering your sidewalk. ‘Tis the season for raised bed building, and may it be a merry season for all.