Raised-bed gardening is a form ofgardening in which the soil is raised above ground level and usually enclosed in some way. Raised bed structures can be made of wood, rock, concrete or other materials, and can be of any size or shape.[1] The soil is usually enriched withcompost.[2]
Vegetables are grown in geometric patterns, much closer together than in conventional row gardening.[2] The spacing is such that when the vegetables are fully grown, their leaves just barely touch each other, creating amicroclimate in which weed growth is suppressed and moisture is conserved.[2]
Raised beds lend themselves to the development of complex agriculture systems that utilize many of the principles and methods ofpermaculture. They can be used effectively to controlerosion 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.[2] 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.
This form of gardening is compatible withsquare foot gardening andcompanion planting.
Circular raised beds with a path to the center (a slice of the circle cut out) are calledkeyhole gardens.[3] 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.
A self watering raised bed known as awicking bed is particularly beneficial in dry climates and are often made by convertingIntermediate bulk container (IBC's).
Lumber is the most common construction material for making raised beds.[2] If using lumbertreated withchromated copper arsenate or CCA (though uncommon since 2004 in the US and Europe[4][5]), it is recommended to use a plastic liner between the wood and soil if the raised bed is intended for growing edibles.[6]
Another material commonly used arerailroad ties, also known as sleepers, joined with steel rods to hold them together. Another approach is to useconcrete blocks, although less aesthetically pleasing, they are inexpensive to obtain and easy to use.
On the market are also prefab raised garden bed solutions which are made from long lastingpolyethylene that isUV stabilized and food grade so it will not leach undesirable chemicals into the soil or deteriorate in the elements. A double skinned wall provides an air pocket of insulation that minimizes the temperature fluctuations and drying out of the soil in the garden bed. Sometimes raised bed gardens are covered with clear plastic to protect the crops from wind and strong rains.[7] Pre-manufactured raised bed gardening boxes also exist.[1] There are variants of wood, metal, stone and plastic.
Raised beds produce a variety of benefits: they extend the planting season,[2] they can reduce weeds if designed and planted properly,[2] and they 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.[7] Waist-high raised beds enable the elderly and physically disabled to grow vegetables without having to bend over to tend them.[7]
Awaffle garden is the inverse of raised beds and is a gardening method by theZuni people. In an arid climate, clay walls are built up around the planting area and plants are watered by filling the bed "cells".[8]
The termsunken garden usually refers to a formal traditionalEnglish garden where the garden is lower than the surrounding land, and may have multiple terraces around it and steps leading down to the garden.[9]
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