Raised Bed Gardening
A raised bed is really just a supersized container.
It can be made from a variety of materials; planks or timber offcuts, logs, stone, railway sleepers, concrete, corrugated sheet material, mounded earth etc.
Using a raised bed system has many advantages, particularly for growing annual vegetables.
Traditionally, you would dig the whole growing area and sow long lines of each vegetable with a path between each row. However, the paths took up an enourmous amount of space and would quickly become compacted. Next year you would start by digging over the whole compacted space again and setting out new rows and new paths. That's lots of digging when the soil is heavy at the beginning of the year.
Raised beds don't get compacted as you never walk on them so are better drained. This is particularly important if you are in an area of high rainfall or on a heavy clay soil.
They provide a much higher yield as plants can be grown closer together and less space is taken up by paths.
Because you don't walk on the beds the soil is easier to work.
Raised beds are ideal for no-dig gardening, you just add a layer of compost on top of your raised bed and let the worms and rain do the work. This also keeps down the annual weeds
It is easier to net brassicas (to keep out cabbage white butterflies) and soft fruit (to keep birds off) as there is a defined base to attach the structure to and secure the netting.
The paths can be covered with mulch, carpet or other materials to keep weeds down.
You can make your raised beds any size and shape to fit into your space. They're normally max 4 feet wide to make sure that you can reach to the middle of the bed from either side.
Raised beds can even sit on top of a solid surface like a patio or parking area.
Setting up costs can be high depending on the materials you choose.
You need to source soil/compost to fill the bed.
There may be more watering to do in dry periods so make sure your soil is 'water retentive'.
There is some maintenence over time as the materials are subject to weather.
Once the beds are in place the layout is fairly fixed (depending on the materials)..
Path width: Will you need to get a wheelbarrow between the beds?
Bed size: Can you reach to the middle of the beds easily?
If your raised beds are quite high (less bending over), you can fill the bottom with rougher earth, and also woody garden waste which will then break down over a season or two, before laying the better soil on top.
If your beds are on hard standing the roots won't be able to penetrate very far down so you may be better off with a higher raised bed if you want to grow anything deeper rooted than salads etc. You will also need to be more aware of the bed drying out.