HOW TO BUILD A RAISED BED GARDEN
Picture building your raised bed garden as if you were making up your idea of the most comfortable sleeping bed in your bedroom at home. A raised garden is 'built' by systematically layering the growth medium from bottom to top beginning with the first or bottom layer.
The surface on which you place your bed is your floor or garden surface. Here you will begin by preparing your bed by layering a carpet in old cardboard on your bedroom floor or garden surface. The importance of this layer is to kill any pre-existing weeds or prevent unwanted plant growth before these can germinate and grow up through your bed.
Now for your bed or base layer of larger logs (the older and more porous, the better). Depending on space available, these logs or tree branches will be layered first. You may find these in some forgotten corner of your yard or nearby vacant land. This base layer will act as a sponge for moisture and home for beneficial bugs in the microbial world.
The mattress layer in your bed will be a mixture of thinner, finer mulch, leaf or bark chips. It is important to note that each layer is complementary and beneficial to each other in terms of creating your own perfect 'bio or ecosystem', for your plants.
This second to the last layer is your compost, sod, or topsoil. The thickness of compost or peat in a reasonably large raised bed of about 800mm or 30 inches need only to be as thick as the root requirements of your vegetables or flowers you choose to plant. I suggest 40 centimetres foot or two of your best available peat or compost.
Finally, once you have planted your seeds or seedlings into your raised garden bed, a warm covering of straw or cut grass as should be used as a top layer. This layer will protect your compost from harsh direct sunlight and moisture loss that your seeds need to germinate into healthy plants.
As time passes your underlying base logs, sticks and mulch will biodegrade down, and the top layer will subside or sink. Top up your raised bed with compost as this happens. Eventually, depending on the size and age of material used to make your garden, all the beneficial microbes, insect and worms will turn your raised garden into an increasingly rich and fertile Eden. This process may take years and many harvests. When this 'final breakdown occurs is the end of the hugelkultur process and will be time to re-build your bed.