Building a raised garden bed: the complete plan for beginners
The raised garden bed has many advantages: no digging, warmer soil in spring, easier access for people who struggle to bend down, and fewer slugs. Building a raised garden bed in boards is a simple project, achievable in a weekend, for about thirty euros of materials. Here is a 120 × 80 × 40 cm plan, easy to adapt.
The dimensions and the soil volume
A 40 cm high bed suits most vegetables and herbs; 50 to 60 cm is better for carrots and long roots, and more comfortable for gardening standing or seated. The width must stay under 120 cm to be able to reach the center without stepping on the soil. For a 120 × 80 × 40 cm bed, allow about 380 liters of potting soil and compost.
- 4 boards of 120 × 40 cm for the long sides
- 4 boards of 80 × 40 cm for the short sides
- Or 200 × 30 cm boards, to be cut to your dimensions
- Stainless steel or galvanized screws of 4 × 50 mm
- Metal brackets to reinforce the corners
- Vegetable potting soil and compost for the filling
Wood suited to contact with the soil
Since the bed is in direct contact with a damp ground, choose a wood that does not rot too fast. Douglas fir and larch are naturally resistant; autoclave-treated pine class 4 is economical. Avoid railway sleepers or woods treated with harmful products, some substances of which could migrate into your vegetables. A geotextile liner at the bottom holds the soil while letting water pass.
- Douglas fir or larch: natural resistance, medium price
- Autoclave-treated pine class 4: economical and durable
- Geotextile or weed-control felt at the bottom, 1 to 2 m² depending on the size
- To avoid: old creosote-treated wood or railway sleepers
The assembly in six steps
- Cut the boards to the chosen dimensions and sand the edges
- Assemble the 4 sides with screws to form the frame, checking the squareness
- Reinforce the corners with metal brackets
- Place the bed in its final location (6 hours of sun per day minimum for vegetables)
- Line the bottom with a geotextile, fixed with small staples
- Fill with vegetable potting soil and compost, mixing roughly
The filling: the layering method
To save potting soil and improve drainage, fill the bed in layers: at the bottom, branches and twigs (about 20% of the volume), then coarse compost, and finally the vegetable potting soil on the surface. This method creates a reserve of organic matter that feeds the plants over the seasons. At the end of the year, top up with 3 to 5 cm of mature compost.
What to plant in a raised bed?
The 40 cm depth and the soil warming faster in spring allow a wide variety of vegetables and herbs to be grown. Combine plants that complement each other: deep roots and shallow crops coexist well in a well-filled bed.
- Lettuce, spinach and arugula: fast growth, harvest within a few weeks
- Tomatoes, cucumbers and zucchini: one or two plants are enough per bed
- Carrots and radishes: then plan a height of 50 to 60 cm
- Aromatic herbs: basil, parsley, chives and mint (in a pot for the latter)
- Strawberries: very productive in a raised bed, easily accessible
Watering and maintenance
A raised bed dries faster than a classic vegetable garden, especially in summer: the soil heats up and the water evaporates faster. Water at the base, preferably in the morning or evening, and mulch to retain moisture. Add mature compost on the surface in spring and autumn to maintain fertility. At the end of the season, remove the wilted plants and leave the soil in place, fed by the year's layers.
The mistakes to avoid
- Filling only with commercial potting soil: the excess peat dries out quickly
- Placing the bed in the shade: most vegetables need 6 hours of sun a day
- Forgetting the drainage: a bottom that holds water rots the roots
- Using treated wood in contact with vegetables without a protective liner
Building a raised garden bed is accessible to all DIYers: a weekend, a few boards of Douglas fir or treated pine, stainless steel screws and a geotextile liner are enough. You get a productive vegetable garden, easier to maintain and warmer in spring. Choose a sunny spot, fill in layers and enjoy healthy vegetables harvested at hand height.