An excellent way to grow vegetables is in beds with raised borders, usually called raised beds. This page looks at both the advantages and disadvantages of raised vegetable beds.
LESS WATER RUNOFF
Ground vegetable beds will inevitably form sloped mounds as they are turned and manure is added. When these mounds are watered or it rains, a proportion of that water will run off the sides of the beds and onto the paths in-between them. Whereas the soil in raised beds remains a flat surface and the top edges of the raised beds form a natural water barrier. This combination insures that almost all the water applied to the raised beds will end up in the beds and not on the paths.
Raised beds have better drainage than the ground below, this is especially so if the ground is low lying or of a heavy clay base.
As the warm of the sun’s rays will be absorbed both on the top and through the sides of raised beds they tend to have warmer soil than vegetable beds at ground level. The advantage of this is that in winter plants will grow faster and in summer, heat loving plants (such as eggplant and capsicum) will be more vigorous.
LESS BENDING WHEN GARDENING
Raised beds mean that you do not have to bend down as far to tend your vegetables, the higher the raised beds the less bending. High raised beds (60 to 80 cm high) will make gardening much easier for the elderly or people with bad backs.
Raised beds remove the sloping sides that develop in ground vegetable beds, which reduces the amount of water runoff.
Raised beds are warmer than ground beds, the higher the raised bed the warmer the soil will be.
Raised beds a more costly than ground vegetable beds. Today there are a range of premade raised beds that are easy to set up and can look very stylish. However, good quality premade raised beds are expensive. You can make your own raised beds for less but the materials are still expensive and there is cost in time required to make them.
Although raised beds offer some flexibility they are less flexible than garden beds on the ground. Beds in a ground vegetable garden can be easily reshaped to move paths around.
HIGHER EVAPORATION RATES
Warmer soil increases the evaporation rate. As raised beds are warmer than ground beds the evaporation rate is higher. The higher the bed, the higher the evaporation rate. If the sides of your raised beds are made of wood evaporation will also occur through the wood, especially if the wood is softwood. As the sun’s rays dry the timber moisture is drawn from the soil through the timber in an osmotic process. If you have wooden sided raised beds higher than 20 cm then it is a good idea to line the insides with builder’s plastic to prevent this happening.