Alternatives to using CCA-treated wood
Cindy Waring asked me privately to post some more information about
alternatives to pressure-treated wood, and I thought others on the list
might be interested as well.
First of all, I need to make a correction to the factoids I posted earlier.
Those random samples from around pressure-treated decks may contain up to 80
times more arsenic than samples taken from surrounding soil, and
pressure-treated wood has been shown to leach 10-35 times more arsenic than
allowed by EPA standards. Sorry for scrambling the data.
Now, according to some of the ORGANIC GARDENING articles in the
aforementioned packet, safer options include
* naturally rot-resistant woods such as cedar and locust (especially native
American black locust, Robina pseudoacacia);
* recycled plastic "lumber" that can be cut and shaped just like wood; and
* wood treated with alkaline copper quat (ACQ), a copper-based chemical
that does not contain arsenic or chromium--not as toxic as CCA.
If you've already used CCA-treated wood, then at least seal it with
polyurethane enamel, acrylic stain, alkyl-resin stain, or spar varnish.
Remember, inhaling the sawdust from CCA-treated wood can be unhealthy, too.
When I assist in the installation of framed raised-bed gardens, regardless
of the situation, I always recommend using yellow pine sealed with this
recipe (from the USDA, surprisingly enough!):
Mix 750ml of boiled (not raw) linseed oil and 30ml of paraffin wax with
enough turpentine to make 4 liters. Dip the wood into the mixture or apply
with a brush. Let dry for a few days before you paint the surface, if you
choose to paint in addition to sealing the wood.
Naturally, in a vegetable garden, I don't recommend painting the wood after
I hope this helps,
Dawn M. Ripley firstname.lastname@example.org
County Extension Agent for Urban Programs www.ca.uky.edu
Cooperative Extension Service, Jefferson County
8012 Vinecrest Avenue, Suite 1
Louisville, Kentucky 40222-4690
(502) 425-0109 fax
community_garden maillist - email@example.com