Guides / Garden · Updated
Is pressure-treated wood safe for raised beds?
From Oregon State, Missouri, Minnesota, Clemson and UF/IFAS extension publications and the EPA, checked November 2026.
Short answer
Today's pressure-treated lumber is generally considered fine for vegetable beds. It's treated with copper (CA, MCA or ACQ), not arsenic, and in Oregon State's study copper rose only within an inch of the boards and not in the vegetables. Buy it rated for ground contact. Avoid old lumber that may be CCA-treated and railroad ties.
What's in treated lumber now
Oregon State Extension: "The most common wood preservatives used for lumber are copper azole (CA-C), micronized copper azole (MCA) and alkaline copper quaternary (ACQ)." Missouri Extension notes ACQ "does not contain arsenic or chromium. It does, however, contain copper."
The arsenic-based one, CCA, is gone from home use: the EPA says manufacturers "voluntarily discontinued manufacturing chromated arsenicals-treated wood products for homeowner uses" in December 2003.
What the research found
Oregon State built raised beds from treated lumber and tested the soil and the crops. Copper rose "only within 1 inch of the bed edge", with "no increase in copper concentration in each of the vegetables and herbs." Their advice: buy lumber treated for "ground contact" and paint the fresh cut ends. Clemson adds that the American Wood Protection Association recommends lumber rated UC4A or higher for horticultural use.
Liners
Extension services differ. Utah State says to put a plastic barrier between treated lumber and the soil; Minnesota suggests lining the edges to cut copper leaching; Missouri and Kansas State call it optional if you're unsure. Given Oregon State's results, a liner is extra caution, not a must. If you use one, line the sides only, so the bed still drains.
What to avoid
- Old treated lumber. Oregon State: "Reusing or salvaging lumber that is over 20 years old may risk introducing CCA-treated lumber." UF/IFAS says not to use treated lumber bought before January 2004 for edibles.
- Railroad ties. They're treated with creosote. Oregon State, Illinois, UF/IFAS and Minnesota all say not to use them.
Not sure? Cedar, redwood and cypress resist rot without treatment (Clemson). Either way, theraised bed plan builder gives you the cut list, andhow deep should a raised bed be covers sizing.
Where the numbers come from
- Oregon State Extension EM 9879, pressure-treated wood in raised bed construction (rev. April 2026)
- EPA, chromated arsenicals (CCA)
- University of Missouri Extension G6985, raised-bed gardening
- University of Minnesota Extension, raised bed gardens
- Clemson HGIC 1257, raised beds
- UF/IFAS ENH1211 (rev. Feb 2025)
- Utah State University Extension, raised bed gardening
- Kansas State MF2134, raised bed gardening