Raised garden beds are a very simple and effective way to establish beds that provide a fertile ground for your plants, drain well, and are easily accessible. Raised beds are especially suited to areas with heavy rainfall (such as the humid tropics) as they ensure that your plants won’t drown during wet season. If you live in an arid region you should consider making sunken beds instead (which are essentially the same, except that you dig down first and make them level with the surrounding soil).
All you need to make raised garden beds is some cardboard, some material that will act as a wall around your bed (logs and branches are great because they decompose, adding more nutrients to the soil, but rocks, bricks, or empty glass bottles also work), some compost or fertile soil to fill in the bed, and some mulch material to put on top.
Select the spot in which you would like to establish your raised bed and loosen the soil with a hoe or a spade as to allow the roots of your plants to penetrate it. Make sure that your bed will be easily accessible later by making it not too wide and having paths around it.
Soak your loosened soil with plenty of water, then thoroughly cover it with sheets of cardboard (make sure to remove all tape and plastic wrapping) – this will prevent unwanted weeds from penetrating into your bed from below. Soak the cardboard with water.
Now you can pile your compost / fertile soil onto the cardboard and build your little wall around it to keep it in place. In the image above we used branches that we had lying around as a border