Raised beds have become popular features in the home landscape. They are both functional and attractive and can be used to grow flowers, vegetables, and small fruits.
Raised beds provide several advantages over conventional garden areas. Wet, poorly drained sites can be improved by constructing raised beds. A properly prepared raised bed increases drainage, thereby promoting plant growth and increasing crop yields. Additionally, raised beds dry out and warm up earlier in the spring which allows earlier planting. Raised beds are more convenient for elderly gardeners or physically challenged individuals who have difficulty bending over to the ground. The raised height of the garden allows these individuals to continue their gardening activities.
While generally minor, raised beds do have some disadvantages. Raised beds dry out faster than level garden sites. Accordingly, they have to be watered more frequently in dry weather. Initial construction of the raised bed may take more effort than maintenance of the conventional garden.
Raised beds may be permanent or temporary structures. Temporary raised beds are shallow beds (6 inches or less in height) constructed within the existing garden. After the garden is tilled in the spring, the loose soil is raked into raised beds. Permanent beds are usually higher than 6 inches in height, have side supports, and are built to last for many years.
The walls of permanent beds can be constructed of decay-resistant wood (such as cedar or redwood), concrete block, rock, or brick. Treated wood and old, weathered railroad ties are other possibilities.
While there are few rules that must be followed, some guidelines should be kept in mind when planning and constructing raised beds. Raised beds should be constructed so an individual can reach everything in the bed without stepping into it. If a raised bed is placed against a building, fence, etc., making it accessible from only one side, the maximum width should be 1 1/2 to 2 feet. Beds accessible on both sides can be 3 to 4 feet wide. The length of the bed is determined by space limitations, personal preference, and convenience. If constructing several raised beds, the pathways between adjacent beds should be wide enough to accommodate garden equipment.
Raised bed soils should be light and well-drained. An excellent soil mix can be prepared by mixing equal parts topsoil, organic matter (well-rotted manure, compost, or peat), and coarse sand.
Before filling raised beds, remove the grass sod (if present) and work up the existing soil with a rototiller or spade. Add a few inches of the soil mix, then incorporate it into the existing soil. Continue to add and incorporate additional soil mix until the raised bed is filled. Incorporating the soil mix into the existing soil prevents the formation of distinct layers in the raised beds. Distinct layers of soil impede water movement and discourage root growth.
This article originally appeared in the May 10, 2002 issue, pp. 57-58.
Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Horticulture and Home Pest News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on May 10, 2002. The information contained within may not be the most current and accurate depending on when it is accessed.