A raised bed is simply a mound of soil on top of the ground. The soil is usually contained by landscape timbers, rocks, cinder blocks or anything else you can think of. Think of it as a huge container.
The raised bed can be as long as you’d like to make it. It is best, though, if you limit the raised bed width to about 4 feet. In a 4-foot wide bed, you should be able to plant, weed and fertilize your raised bed without ever having to step into it. This eliminates a lot of compaction — which means less time tilling and getting the soil ready to plant. I’ve never tilled my raised bed. Adding organic matter between plantings will keep the soil nice and loose. Depth should vary from 8–18 inches. I try to make the beds at least a foot deep to allow adequate space for plant roots.
Why go raised?
• Quality soil. Many people are limited by problem soil. At first glance, the soil may seem great — the top inch anyway. Upon further inspection many find their soils perfect for rock gardening. You know the type — you pull out one rock only to find five more have taken its place. With a lot of work and patience, these soils can become great vegetable gardening spaces, but many choose to forgo the rock work and build a raised bed. Raised beds are filled with quality potting mixes and organic matter creating a well-drained, nutritious soil. The downside to this is the initial expense of filling the beds with the soil.
• Space concious. Typically, raised beds work in smaller areas than traditional in-ground gardens, which makes them more convenient for those with limited space. In a smaller space, plants are planted a little closer together — more vegetable plants for the space. The dense plant canopy helps keep weed seeds from germinating. Again, for every pro there is a con. When plants are spaced closer together, the incidence of disease and insect damage may be greater.
• Early planting. Raised bed soils will warm up a little faster in the spring. Because of this, planting a little earlier is doable. That’s great news for those in a rush to plant. A word of caution: Because the soils are raised, more attention to watering is necessary. Raised beds will dry out faster than in-ground gardens.
• Economical. The expense of tilling and other equipment is usually nil. Hand mixing the soil mixture is all that is needed. Because of the easy access to the raised bed you can work in it after a big rain or even during a rain. No need to wait until the soil dries to till your garden!
• Stylish. Raised beds can be a focal point in the landscape. I’ve seen many beautiful raised beds made out of huge rocks harboring vegetables, herbs and flowering plants. Of course, I think raised beds made of any materials can provide a great place to grow vegetables that look good too!
There is some work that has to be done before a constructing a raised bed. First remove all the grass and other vegetation from the ground. It is preferable to loosen or spade the soil underneath the raised bed. To a depth of 6–8 inches. This native soil can be used within the raised bed. Blending the two together helps avoid problems that may arise when two different soil layers meet abruptly. Mix it with the potting mixes and organic material within the bed. Acquiring potting mixes and organic material can be a chore if using the small bags. Some municipalities offer composted material from their recycling centers.
Remember a raised bed is still a vegetable garden and the rules of a traditional in-ground gardening still apply. Full sun is necessary, fertilizer is necessary, as is pest control. For more ideas, take a look at the Alabama Cooperative Extension System’s guide on raised bed. In it you’ll find building material plans, costs, planting plans and lots of other great information. Go to www.aces.edu and search “raised beds.”