Raised-bed gardening is a form of gardening in which the soil is formed in 3 – 4 foot (1.0–1.2 m) wide beds, which can be of any length or shape. The soil is raised above the surrounding soil(approximately 6 inches to waist-high), is sometimes enclosed by a frame generally made of wood, rock, or concrete blocks, and may be enriched with compost. The vegetable plants are spaced in geometric patterns, much closer together than conventional row gardening. The spacing is such that when the vegetables are fully grown, their leaves just barely touch each other, creating a microclimate in which weed growth is suppressed and moisture is conserved. Raised beds produce a variety of benefits: they extend the planting season, they can reduce weeds if designed and planted properly and reduce the need to use poor native soil. Since the gardener does not walk on the raised beds, the soil is not compacted and the roots have an easier time growing. The close plant spacing and the use ofcompost generally result in higher yields with raised beds in comparison to conventional row gardening. Waist-high raised beds enable the elderly and handicapped to grow vegetables without having to bend-over to tend them.
Raised beds lend themselves to the development of complex agriculture systems that utilize many of the principles and methods of permaculture. They can be used effectively to control erosion and recycle and conserve water and nutrients by building them along contour lines on slopes.This also makes more space available for intensive crop production. They can be created over large areas with the use of several commonly available tractor-drawn implements and efficiently maintained, planted and harvested using hand tools.
Circular waist high raised beds with a path to the center (a slice of the circle cut out) are called keyhole gardens. Often the center has a chimney of sorts built with sticks and then lined with feedbags or grasses that allows water placed at the center to flow out into the soil and reach the plants’ roots. The charity Send a Cow is promoting the creation of these in Africa.