Raised beds warm up earlier in spring, drain better on heavy clay and save your back. Paired with a greenhouse, they give you room outside for everything the greenhouse raised from seed.
How wide?
Keep a bed no wider than about 1.2 m. You then reach the middle from both sides without stepping on the soil, which keeps it loose. Against a wall or fence, keep it to about 60 cm, as you only reach from one side.
How deep?
- 30 cm: enough for salad leaves, herbs, radish and onions.
- 45 cm or more: better for carrots, parsnips and potatoes, and you bend less.
- On a hard surface such as a patio, go deeper still, as roots have nowhere else to go.
Metal or timber?
- Galvanised or powder-coated metal: lasts many years, goes together with bolts, warms up quickly in spring.
- Timber: looks natural and is easy to cut to size, but untreated wood rots in a few years. Line the inside with a membrane to make it last longer.
On soil, choose a bottomless bed, so worms and roots move freely between the bed and the ground below.
How to fill a raised bed
Filling a deep bed with bought compost gets expensive. Build it up in layers instead:
- Branches, twigs and coarse prunings at the bottom.
- Turf turned upside down, leaves and garden waste.
- Topsoil.
- A top layer of good compost, at least 15 to 20 cm.
The lower layers break down over time, so top up with compost every spring.
Layout
- Leave paths wide enough for a wheelbarrow between beds.
- Put beds in full sun where you can.
- Run beds north to south, so both sides get the same light.
With a cold frame
A cold frame on top of a raised bed gives you an early start in spring. Some, like the Christow Raised Bed Cold Frame, come as one unit.
Our picks for metal raised beds are below. More kit under grow your own.
