MCA Treated Timber sold as safe for community garden beds please advise

Asked June 12, 2019, 11:20 AM EDT

Are timbers pressure treated with MCA safe for community garden beds? HOME DEPOT recommends these for vegetable gardens, as in 8 ft by 4x4 timbers, using rebar as a connector. Our original beds were built with 12x4ftx2in lumber, untreated, using deck screws, as recommended by your community garden advisor from Harford County Extension Office. We are planning to build this Saturday, must get the Purchase order in today to get the check for Home Depot. I have not seen plans to build with 4x4 timbers using rebar, and would like an answer today. please call 443-807-9770.

Harford County Maryland

1 Response

We do not have information indicating that wood treated with Micronized Copper Azole (MCA) should not be used for constructing vegetable garden beds. MCA is a water-based wood preservative that uses less copper than other preservatives. There is some copper naturally in soil and plants need a little bit of copper for good growth. The National Pesticide Information Center is a good resource for current information on wood preservatives and their use in gardens.