Garden Notes·Raised Garden Beds
Raised Garden Beds: Sizes, Materials and How to Fill Them
How wide, how deep and what to build them from — plus a simple way to work out how much soil a raised bed needs.
By GardenHelm Editors··2 min read
Raised beds warm up faster in spring, drain better than heavy ground and put plants within easier reach. They are one of the most practical upgrades for a vegetable garden. Here is how to plan them.
Width: reach the middle without stepping in
Keep beds narrow enough to reach the center from either side — around 3 to 4 feet wide works for most people. Against a fence or wall, where you can only reach from one side, keep it nearer 2 feet. Not stepping on the soil keeps it loose.
Depth: match it to what you grow
Shallow-rooted crops such as lettuce and herbs manage in about 6 to 8 inches of good soil. Most vegetables are happier with 10 to 12 inches, and deep-rooted crops such as carrots and tomatoes appreciate more. If the ground underneath is poor or compacted, a deeper bed helps. Taller beds also mean less bending, but need more soil.
Paths
Leave paths wide enough for a wheelbarrow or garden cart — often around 2 feet or more. Mulch, gravel or pavers keep them clean and weed-free.
Materials
- Untreated rot-resistant wood such as cedar is a common choice. It weathers to gray over time.
- Metal (often galvanized or coated steel) beds last a long time and suit modern gardens. They can warm up in direct sun.
- Composite boards resist rot and need little upkeep.
- Stone, brick or block beds are permanent and sturdy.
If you are considering treated lumber for an edible garden, read the manufacturer’s guidance and your local extension service’s advice first.
How much soil do you need?
Multiply length × width × depth in feet to get cubic feet. For example, a 4 × 8 ft bed filled 1 ft deep needs about 32 cubic feet of soil — a little over one cubic yard (27 cubic feet). Bagged soil is sold by the cubic foot; bulk soil is sold by the cubic yard. Soil settles, so plan to top up after the first season.
What to fill it with
A blend of quality topsoil and compost is a common starting point, and many suppliers sell ready-made raised-bed mixes. Avoid filling a bed with straight potting mix, which is designed for containers. A soil test from your local extension service tells you what, if anything, to add.
Placement
Most vegetables need at least 6 to 8 hours of direct sun. Place beds where you can reach them with a hose or drip line — raised beds dry out faster than ground beds, so easy watering matters.