What are Raised Beds?
Raised gardening beds are constructed "containers" which hold the soil and
plants higher than the level of the ground. They can be as low as 4 to 6
inches to separate the area from a lawn, or higher so older gardeners can
sit down while they garden and people in wheelchairs can easily reach their
Why have Raised Beds?
There are several good reasons to build raised gardening or planting beds
as part of a greening project.
- While a ground-level bed requires stooping and kneeling to reach the
plants, raised beds bring the plants up to a level where they are easier to
reach for people with physical disabilities.
- Raised beds allow you to garden on top of pavement. In many instances, it
is less expensive and less complicated to build raised beds on top of
asphalt or concrete than it is to break up, remove and dispose of these
- Soil with high levels of lead are unsuitable for vegetable gardening.
Again, instead of removing the soil which contains lead, you can garden
successfully in a raised bed with newly-purchased topsoil.
- Raised beds effectively separate planted areas from active areas where
people walk, play, drive, or do other things which might damage plants. In
playgrounds or next to pathways, raised beds keep plants on another level,
away from feet and wheels.
- A raised bed concentrates the topsoil into the planting area. Move the
good soil from the paths and walkways into the beds and lay other
surfacing, such as woodchips or stone dust, down where you aren't growing.
- 18 to 24 inches is a perfect height for a seat. The edge of a raised bed
often doubles as a seat or bench for people to rest upon and enjoy the
garden or outdoor space.
- Soil in raised beds dries out more quickly than soil at ground level and
will require more watering. This soil also warms up more quickly, giving
early spring plantings a head start.
Building Raised Beds
Size and shape: A raised bed can be any shape, but typically they are
rectangular or square because they are constructed with lengths of wood.
When designing or building a raised bed it is important to remember that
gardeners will probably need to reach the center of the bed from the edge.
Therefore, it is recommended that you keep the width of the beds narrower
than four feet wide for gardens. They can be as long as you like. If the
bed holds another type of planting, such as trees and shrubs, they can be
wider. The higher the bed the more expensive it will be to construct and
fill with soil.
Hint: If your bed is deeper than 18 inches, use stone, sand, gravel, or
another clean fill as the bottom layer and save on topsoil costs.
Materials: Wood is a good, relatively inexpensive material to choose.
Keep in mind that wood eventually rots when it sits in contact with water;
therefore you should consider approved types of pressure treated wood. CCA
40-year wood has been approved by the FDA for use in contact with garden
soil. (CCA stands for copper chloride arsenic and the wood is rated to last
outdoors for at least 40 years.) If you wish to take further precautions
against the chemicals in the wood you can line the inside of the bed with
plastic before you fill it with soil. Do not use old wood that has been
painted with lead paint, used rail road ties, or unapproved
pressure-treated wood. These may add contaminants to the soil.
Stone, brick, cobblestone, or other masonry is also suitable for low beds.
It is more difficult to construct taller beds with these materials. Poured
concrete is quite an investment and is not as asthetically pleasing, but
will last a long time. Do not use asphalt as an edge for a bed. It
contains petroleum products that may contaminate soil.