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How to Build a Raised Garden Bed for Vegetables

A raised garden bed is a contained growing space built above ground level, typically 8-12 inches high and filled with quality soil mix. You'll build a rectangular frame from cedar or composite boards, level it on your chosen site, fill with a blend of compost, topsoil, and amendments, then plant your vegetables in the improved drainage and soil conditions.

Ingredients

Step by step

  1. Choose your location and measure. Pick a spot that gets 6-8 hours of direct sunlight. Mark out a rectangle no wider than 4 feet so you can reach the center from either side. Common sizes are 4x8 feet or 4x4 feet. Clear the area of grass and weeds.
  2. Cut your lumber. Use untreated cedar, redwood, or composite boards that are 2 inches thick and 8-12 inches wide. For a 4x8 bed, cut two pieces at 8 feet and two pieces at 45 inches (to account for the thickness of the end boards).
  3. Assemble the frame. Lay the boards on a flat surface. Drill pilot holes through the short boards into the ends of the long boards. Secure with 3-inch exterior screws or galvanized carriage bolts. The frame should form a tight rectangle.
  4. Level the ground. Place the frame on your marked area. Use a level to check all sides. Dig out high spots or add soil to low areas until the frame sits evenly. The top edge should be level all around.
  5. Prepare the base. Lay cardboard or newspaper inside the frame to suppress weeds. Poke holes for drainage if using cardboard. This barrier will decompose over time but prevents grass from growing up into your bed.
  6. Fill with soil mix. Fill with a blend of 1/3 compost, 1/3 topsoil, and 1/3 coarse vermiculite or perlite. This creates loose, well-draining soil. Fill to within 2 inches of the top edge. Water thoroughly and let settle for a few days.
  7. Top off and plant. Add more soil mix to bring the level back up after settling. The soil should be loose and crumbly. Now you can plant your vegetables according to their spacing requirements.

Tips & troubleshooting

Variations

Questions

How deep should a raised bed be for vegetables?
Most vegetables need 8-12 inches of soil depth. Lettuce and herbs can manage with 6 inches, while root vegetables like carrots need at least 12 inches. Tomatoes and deep-rooted plants prefer 18+ inches.
What type of wood is safe for vegetable gardens?
Cedar and redwood are naturally rot-resistant and safe. Avoid pressure-treated lumber as the chemicals can leach into soil. Composite lumber made for garden beds is another good option.
How long will a cedar raised bed last?
A well-built cedar bed typically lasts 10-15 years before the boards need replacing. The bottom boards that touch soil will rot first, usually after 7-10 years.
Do I need to remove grass under the bed?
No need to dig up grass. The cardboard barrier and soil weight will kill the grass underneath. The decomposing grass actually adds organic matter to your growing area.
How much soil do I need to fill a raised bed?
Calculate length × width × depth in feet, then multiply by 7.5 to get gallons needed. A 4x8x1 foot bed needs about 240 gallons of soil mix.

Further reading