For poor soil, for gardening on rooftops or balconies or just to cut down on weeding, mulching and tilling, a raised bed can be an asset for gardeners. Raised beds can also elevate the soil level so that the elderly or arthritic can easily grow gardens. When given the right soil and water conditions, many types of plants can grow in a raised bed.
Each vegetable plant needs a minimum of five gallons of soil. In containers, there is often not enough soil, but a raised bed provides more than enough soil for vegetables to thrive. According to the Phoenix Permaculture Guild, vegetables are ideally suited to raised beds in areas where rodents such as squirrels and gophers live. The raised beds can be protected at root level with barrier cloth, and can be caged with chicken wire to prevent access from the outside. In cooler climates, raised beds heat up faster than the ground, which can extend the growing season of veggies.
In the article "Garden Spaces for Small Places," Dorothy Ainsworth states that fruit trees can be grown in raised beds if the trees are grown against a fence or wall for support. This type of tree is known as an espalier. The key to growing an espalier in a raised bed is to cut off any branches that do not grow laterally. This way the tree can fit into compact spaces. Fruit trees may also be trained so that their branches grow in a fan shape by staking the branches for a short time against a wall to train them.
If you have leftover brick from a home project, or if you purchase brick retaining wall pavers, you can construct raised beds for shrubs or other ornamental plants. Brightly colored annuals can be planted in raised beds to raise them up and make them more noticeable. Roses will do well in raised beds because you can more precisely control the conditions of the soil around them, as well as staking climbing roses to the side of your house to give them support. Finally, ornamental shrubs such as boxwood that do not like wet soil will do well in a raised bed where proper drainage can be assured. This is particularly the case for homes where the lawn does not have a proper grade to insure that the drainage in the ground is adequate.