A "raised bed" is a gardening term referring to an elevated box, usually for growing flowers or vegetables but also trees or shrubs. The sides of the raised beds may be made with landscape lumber, railroad ties or concrete blocks. Raised beds can be beneficial to the people who use them and the plants that grow in them.
The height of the raised bed can be beneficial to a person who desires to garden sitting down. Some raised bed designs include a ledge on which the gardener may sit, or the gardener may be in a wheelchair. That elevation also promotes faster warming, so the raised bed can be planted one to two weeks earlier in the spring than a ground-level garden. A tall elevated bed may also deter dogs from digging in the soil.
Many gardeners face soil composition high in clay and stones. Clay soil, which compacts easily, needs to be amended to produce robust plants. Raised bed owners can choose what type of soil they want, such as rich top soil, potting soil or other humus blends, and all without stones. The soil of a ground-level garden will become compacted from foot traffic while in a raised garden, the soil remains more loose, allowing oxygen and nutrients to more readily reach plants' roots.
The roots of flowers and vegetables typically reach no more than 12 inches below ground. Heavy rains that can leave ground soils saturated will not impact a raised bed, so the plants' roots are not standing in water. When watering a ground-level garden, the water can run horizontally away from the roots, requiring longer sessions. Water is confined horizontally within the sides of a raised bed.
Plants that tend to spread easily, like lily-of-the-valley, Mexican evening primrose or mint, will not make their way out of a raised bed, saving the rest of the landscape from an evasion.