Reference
Is Pressure-Treated Wood Safe for Raised Beds?
The short answer
Pressure-treated lumber sold for residential use since 2003 is treated with copper-based preservatives such as alkaline copper quaternary (ACQ) or copper azole, which contain no arsenic. This replaced the older CCA (chromated copper arsenate) lumber, which is the source of most lingering safety worry.
Extension research on the newer copper-treated wood found it raised soil copper only slightly, and only within about an inch of the board, with no measured increase of copper in crops grown in the beds. The main caveat: certified-organic standards still prohibit pressure-treated wood in soil used to grow organic food, so lining the boards or choosing untreated wood remains an option if that matters to you.
Old wood vs. new wood
The health concern many gardeners remember is arsenic from CCA-treated lumber, which was phased out of residential sale at the end of 2003.
Wood you buy today is treated with copper-based systems (ACQ, copper azole, including micronized copper azole). These do not contain arsenic or chromium.
What the research found
Oregon State University research on copper azole-treated raised beds found soil copper increased only slightly and only within roughly one inch of the board edge.
In their trials, copper levels in crops — including root crops — grown in the treated beds were not higher than in untreated-wood beds.
If you still want to be cautious
You can line the inside of the boards with heavy plastic sheeting to separate soil from wood, or simply use untreated rot-resistant species, brick, or concrete block.
Note that certified-organic production does not permit pressure-treated wood in contact with soil growing organic food, per state agriculture guidance — a rule worth knowing if you sell or certify your produce.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- Oregon State University Extension — Pressure-treated wood for raised bed construction — Modern ACQ/copper azole lumber is arsenic-free; soil copper rises only slightly within ~1 inch of the board; no increase measured in crops, including root crops.
- University of Maryland Extension — The Safety of Materials Used for Building Raised Beds — Post-2003 residential treated lumber uses copper-based, arsenic-free preservatives; lining with plastic is an option; untreated and non-wood materials also suitable.