How to build a raised garden bed
- Pick a sunny, level spot. Most vegetables want 6–8 hours of direct sun. Set the bed where you'll walk past it — out of sight is out of mind.
- Size it so you can reach the middle. Keep beds 3–4 ft wide and any length. Leave 2 ft paths between beds for a wheelbarrow.
- Build the frame. Untreated cedar, hemlock, or composite lasts longest; a 2-board-high frame (about 10–12 in) suits most crops. Corner posts or brackets keep it square.
- Loosen the ground and lay cardboard. A layer of plain cardboard on the soil smothers grass and weeds while letting roots and worms through.
- Fill with a good mix. Use the calculator above for quantities. Mel's Mix — ⅓ compost, ⅓ peat or coir, ⅓ vermiculite — is the gold standard, or blend quality topsoil with compost 50/50.
- Water it in and top up. Soak the bed, let it settle a day, then add more mix to bring it back to the top.
How deep should a raised bed be?
- 6 in — fine for lettuce, herbs, radishes and other shallow-rooted greens if the bed sits on open soil.
- 10–12 in — the all-purpose depth for most vegetables.
- 18 in+ — best for deep feeders like tomatoes, carrots and potatoes, and a must if the bed sits on concrete, gravel or a deck.
The best soil mix for raised beds
Raised beds live or die by their soil. Don't just shovel in native dirt — it compacts and drains poorly in a frame. Aim for a light, rich blend:
- Mel's Mix — equal parts (by volume) compost, peat moss or coconut coir, and coarse vermiculite. Drains well, holds moisture, feeds plants.
- Simple 50/50 — good-quality screened topsoil blended half-and-half with compost, if buying the three-part mix isn't practical.
- Feed it every year. Add 1–2 inches of fresh compost each spring to replace what the last crop used.
What grows best in a raised bed?
Almost everything — but raised beds shine for crops that love loose, warm, well-drained soil: tomatoes, peppers, lettuce and greens, carrots and root crops, bush beans, herbs, and strawberries. Use the planting calendar to time each one to your zone, and keep the deer-resistant plant finder handy if deer share your yard.
Raised bed FAQ
- How much soil do I need for a 4x8 raised bed?
- A 4 ft × 8 ft bed filled 12 inches deep holds 32 cubic feet — about 1.2 cubic yards, or roughly 21 bags of 1.5 cu ft soil. At 6 inches deep it's half that. Use the calculator for your exact depth.
- Can I use bagged garden soil to fill a raised bed?
- Yes, but read the label — "garden soil" and "raised bed mix" are formulated to fill beds, while "potting mix" is lighter and pricier and better for containers. For a big bed, bulk soil by the cubic yard is far cheaper than bags.
- Do I need to line the bottom of a raised bed?
- No plastic — it traps water. Lay plain cardboard or several sheets of newspaper to block weeds; it breaks down and lets roots reach the soil below. Add hardware cloth under the bed only if burrowing rodents are a problem.
- How wide should a raised bed be?
- 3–4 feet, so you can comfortably reach the center from either side and never have to step in the bed and compact the soil.