The purpose of a raised bed vegetable garden is usually to increase crop yield and control soil quality. The beds are often constructed such that the bed is 3-4 feet across, 6-10 feet long, and elevated above ground level. Raised beds are usually separated by paths that allow the gardener to plant, weed, and harvest from.
Raised bed gardening allows vegetable gardening to be carried out in any location, regardless of the surrounding soil condition. Additionally, this method of gardening promotes higher crop yields due to condensed planting (vegetables in a raised bed garden are usually planted close to each other) and companion planting. The close proximity of maturing vegetables creates an environment underneath the near-touching foliage, where weeds are suppressed and moisture is retained.
A raised bed garden tends to provide better drainage due to its elevation above the surrounding soil. The elevation prevents water from pooling (this is not an excuse to over-water!)
Raised bed gardening often produces vegetables more efficiently due to the custom-built condition of the soil within the bed. A good mixture of fertile topsoil (or organic potting soil) and compost is the most popular blend. Additionally, the soil in a raised bed vegetable garden will not become compacted from foot traffic and therefore will stay loose, maintaining aeration. The deep, loose soil will encourage plants to root deeply.
A raised vegetable garden will deter crawling and burrowing pests such as slugs/snails and gophers/moles/voles due to the raised nature of the bed. We also recommend that the bottom of the raised beds be enclosed with an appropriate wire mesh to keep animals from burrowing under. See our page on vegetable garden fences to match the mesh with the pests in your area.
The side-walls of a raised vegetable garden prevent soil from being washed away during heavy rains. As an additional precaution, we recommend using as wide a board as possible when building a bed enclosure. This reduces the number of horizontal cracks in the bed walls from which water and nutrients can drain.
The soil within a raised bed will often warm earlier (than the surrounding ground) in spring, allowing vegetables to be planted a bit sooner.
A raised vegetable garden prevents gardeners from bending all the way to ground level, easing back strain. A wide sill around the edge of the walls prevents further strain by allowing the gardener to sit while working. Note: Be sure to build a your beds no more than 4 feet across. This will allow easy reach to the middle of the bed.
The ability to control the quality of the soil within a raised bed garden allows vegetables to be condensely planted. Fertile soil combined with condensed planting will tend to produce higher vegetable yields.
These beds are easy to cover due to their defined area, allowing coverage from; (1) Frost in early spring/late fall, and; (2) The hot sun in mid-summer.
Raised bed gardening is usually carried out by building 4-foot wide enclosures from wood, plastic/composites, concrete or rock. It is best to build these enclosures to support soil that is at least 12 inches of soil. Waist-high raised beds will provide the least amount of bending over to work, preventing back strain. The recommended material for a raised bed vegetable garden enclosure is hardwood. We strongly recommend that treated materials are not used as they tend to leach chemicals into the soil.