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Raised Bed Gardens: Basic Construction

Raised bed gardening is very popular and offers gardeners several advantages. One major advantage for the Ozarks is that you can garden anywhere, whether you have good soil or not. Raised beds offer improved internal water drainage, where water drains from the soil surface down to the layers below the roots. It is more difficult to inadvertently walk on your garden area and compact the soil when the bed is surrounded by a frame. You can grow more plants in a smaller space due to the addition of enriched soil/media. There is no need to till or weed between rows as in a traditional vegetable garden and raised beds are easier to weed due to higher density planting and a richer, “fluffier” soil mix. Last but not least, the soil in a raised bed will warm up earlier in the spring giving you a jump start on the season.
There are some disadvantages, however. The beds will dry out faster and are more expensive initially than a traditional garden in the ground. If you have cats, they may get the mistaken notion that you have constructed a giant litter box just for them! The advantages of raised bed gardening, in my opinion, outweigh the disadvantages.
Of the three types of raised beds – raised ground beds, supported or framed raised beds and raised bed planters – the most common are raised beds supported by a frame. Here we cover where to site your raised bed and basic frame construction.
First, you need to decide on a site for your raised bed. You want to locate it in full sun (6-8 hours of sunlight per day), accessible to the house and close to a water source. You need to include at least 2 feet of room between the beds in order to kneel and work. If you plan to mow in between the beds, the distance between them needs to accommodate the width of you mower.
Raised beds should be at least 6 inches high, although you may want to have them 12 inches high if you are growing root crops. You can make them higher and narrower for wheelchair access if you need to. Keep the width of the beds no more than 4 feet so you can reach into the center from either side of the bed. If your bed is located against a wall or fence, make them only 2 to 3 feet wide. If the length of the bed is longer than 6 feet, you may need additional bracing (a stake or other reinforcement) every 4 to 6 feet or so.
The frame for a raised bed can be made of many different materials including cedar, unplanned, untreated boards with thicker, 2 inch sides, landscape timbers, recycled plastic boards or left over composite decking material, metal, cinder blocks, landscape brick, and rock. Some references do not recommend pressure treated wood while others do. The ACQ pressure treated wood is recommended for use in garden structures by the EPA. Using wood treated with creosote or CCA is not recommended.
There are several ways to build the corners of your box. Use galvanized nails to secure the corners, lapping the board ends or using a stake to reinforce the corners. I like the grow-box raised bed pallet style corners since they are easy to use for someone who does not do a lot of woodworking (like me). These are available from Lee Valley http://www.leevalley. com/en/garden/, but there are also a lot of raised bed kits or corner sets on the market.
Remember, fall is a great time of year to construct your raised beds and fill them with soil and organic matter before spring. Raised bed kits also make excellent gifts for the gardeners in your family. So, grow on and give raised bed gardening a try.
Direct comments or questions concerning this column to Marilyn Odneal via email at  write to Missouri State Fruit Experiment Station, 9740 Red Spring Road, Mountain Grove, Mo. 65711; or call (417) 547-7500. Visit our Web site at