Are pressure-treated timbers safe for vegetable gardens?

Modern ACQ-treated timber is generally considered safe, but many gardeners prefer cedar or line the inside with plastic as a precaution.

How do I stack landscape timbers?

Offset joints between courses and pin together with 12-18 inch rebar or structural timber screws every 4 feet.

Landscape Timbers

Landscape & Outdoor

Borders & Edging

Budget: $5-$8 each (3x5x8 treated) | Mid-range: $10-$18 each (4x6x8 treated) | Premium: $20-$40 each (6x6x8 treated or cedar)

Landscape Timbers: Pressure-Treated Wood for Borders & Raised Beds (2026)

Prepared by Lumberama's Building Materials Team

|Last updated May 25, 2026|Sources & methodology

Landscape timbers are milled wood beams used for garden borders, raised beds, small retaining walls, and outdoor steps. Standard dimensions are 3x5 or 4x6 inches in 8-foot lengths. Pressure-treated timbers resist rot and insects for ground-contact applications, while cedar offers a natural alternative.

Key Features

Pressure-treated for ground contact; Standard 3x5 and 4x6 sizes; 8 ft standard length; Stackable for raised beds and walls; Natural and treated options available

Specifications

Sizes: 3x5x8 ft

4x6x8 ft

6x6x8 ft | Material: pressure-treated pine

cedar | Treatment: UC4A ground contact rated | Weight: 30-60 lbs each | Fastening: rebar or timber screws

Applications

Garden bed borders and edging; Raised garden beds; Low retaining walls (under 2 feet); Outdoor stair construction; Playground borders

Installation Overview

Level ground and lay first course of timbers. Drill holes every 4 feet and drive 18-inch rebar through timber into ground. For stacked courses, offset joints and pin with timber screws or rebar. Use landscape fabric behind walls to prevent soil migration.

Pros & Cons

Pros

✓ Easy to cut and install; Affordable border material; Stackable for height; Long-lasting when treated

Cons

✗ Pressure treatment chemicals near food gardens debated; Heavy to handle; Can twist and bow over time; Not suitable for tall retaining walls

Top Brands

Available at all major lumber yards (generic commodity)

Code Requirements

Retaining walls over 4 feet require engineering in most jurisdictions. Ground contact requires UC4A treatment minimum. Check local codes for setback from property lines. Food garden proximity to treated wood debated - use UC4A or cedar.

Buying Tips

Hand-pick timbers at the store - reject any that are severely twisted, bowed, or cracked; Use 18-inch rebar stakes to pin timbers securely to the ground; For vegetable gardens, consider cedar timbers or lining treated timbers with food-safe plastic