Temporary raised beds made with a tractor and a bed shaper.

Two basic types of raised beds are used today. One uses some type of border to maintain the shape of the bed. These are referred to as permanent beds. The other is borderless and, although less expensive to build, by its very nature is temporary.

Temporary beds are usually formed with a tiller or tractor-powered bed shaper. Much of the commercial vegetable production around the world is achieved on temporary beds. This production tends to be located on Class 1 soils — typically well-drained, loamy soils. These qualities enable them to be worked over a wider range of soil moisture conditions. Therefore, as a rule, permanent raised beds can't be justified on these types of soils. Permanent beds are ideal, however, on sloped ground or on soils that possess a high clay content and drain poorly. Permanent beds effectively overcome the drainage limitations of tight clay soils. Erosion can be controlled on hillsides with the use of terraces and permanent beds.

The Bootstrap Community Garden, built of 1-inch by 6-inch lumber, in Ardmore, Okla.

Permanent beds utilize borders to contain the growing medium. Without borders, temporary beds are susceptible to erosion from rainfall and need continuous reforming. Unlike temporary beds dependent on fair weather for bed formation, permanent beds are always ready for service, even during periods of heavy rainfall. Seeding, transplanting and harvesting schedules can be maintained to a greater degree during adverse weather.

Some additional advantages of permanent beds involve bed height and versatility. Many individuals are not able to work in a typical raised bed garden due to physical limitations. Permanent beds can be adjusted to chair height or even waist height to accommodate gardeners with special needs.