What is a raised bed
A “raised bed” is created by adding a layer (at least a foot) of soil on top of the existing soil, using a frame to keep the soil in place. Instead of digging down in to the soil therefore, you are effectively raising the level of it up by a foot. The raised bed is therefore an ingenious cheat to provide good quality, deep, fertile soil that’s perfect for planting.
Why use them
Generally speaking you need a good spade’s depth of quality top soil in order to grow decent veggies. Urban and suburban GIYers face the issues of poor soil quality in their garden, and lack of time to spend improving the soil quality. In most housing estates in Ireland for example the ‘soil’ was created by departing builders throwing a miserly inch-thick layer of top soil on top of the builder’s rubble, good luck growing anything nutritious in that.
Benefits of raised beds
Designing your raised beds
You must be able to reach the centre of the bed from the sides. A 1 metre wide bed is therefore considered ideal, depending on the length of your arms I suppose, because the centre of the bed can be reached from both sides. But don’t push it up against a wall!
The beds should be a minimum of 25cm deep. You can go as deep as you want, even up to waist height. Deeper beds have the advantage of being easier to work at, no bending or kneeling. But if they are expensive to fill with soil, they drain very quickly and are therefore difficult to keep watered in summer. A false bottom in a very deep raised bed might be a bit more complicated to make but it raises the bed to a very convenient height and cuts down considerably on the amount of soil and water needed.
A typical argument against raised beds is their cost. In reality, you can spend as much or as little as you want. You can buy raised beds flatpack, have them made for you by a local tradesman or make them yourself from old scaffolding planks or salvaged timber (we use recycled pallet wood).
The Basic 5 Step Plan to Make Raised Beds
1. Measure out the lengths of wood needed, cut them to size and screw them together.
2. Support from the inside using wooden pegs at each corner, then screw the planks to the pegs for support.
At this point move your raised bed to its proposed location. Check you can access all the way around it and that you can reach the centre.
3. Place a thick layer of wet cardboard and/or newspaper on the ground beneath to kill off grass and weeds.
4. Fill with compost and top soil. A mix of about 70 per cent soil and 30 per cent compost is ideal.
5. Fill the beds to within about 10cm of the top so that the sides of the bed act as a windbreak.
You can buy top soil in garden centres but it will be expensive. Specialist soil mix providers like Enrich sell larger quantities (1-tonne bags). Ask at your local GIY group, gardening club, or allotment organisation. Failing that, keep an eye on local papers, adverts sites and social media for people getting rid of topsoil. Ask to see the soil before it’s delivered, you do not want a lorry load of subsoil full of stones and weeds.