There are only a few guidelines to follow when constructing a raised bed vegetable garden. Keep the beds narrow and match their length to watering systems. A north-south orientaion is best for lower growing crops, allowing sunlight to both sides of the bed. An east-west orientation is best for taller growing vegetables such as pole beans, corn, caged tomatoes and okra. Thus lower growing vegetables could be planted on the south side of the bed and still recieve full sun.
Avoid the use of creosote or pentachlorophenol-treated lumber as these agents are toxic and will leach into the garden soil and injur plants, and you as well. Use pressure treated lumber, stone, wall blocks, or brick.
The soil in the bed should consist of at least one-third native soil, even if it is heavy clay. Blend the native soil with plenty of compost adding sand if you like to achieve sufficient soil level in the bed. Have a soil test done to test for pH or add about 40 lbs of pelletized lime per 500 sq. ft. of bed space to adjust ph.
Raised bed possibilities are endless. Beds of 24" or higher require very little bending to work in the garden. Benches can even be built to make working in the garden even easier. Because raised beds warm up quicker than the ground they can easily be used as a cold frame by covering with clear plastic, allowing then to be planted earlier and protected during a late cold spell. Supports for poles, cages, or trellises can be mounted to the frame for longer life and ease of installation or removal.
Perhaps the easiest and most practical way to build a raised bed is with landscape timbers. Treated landscape timbers, as shown in the diagram below, are available in several sizes make an attractive bed and last for many years. Research has shown that the treatment used on these timbers does not leach into garden soil and injur plants. However, if you want to be on the safe side, line the timber sidewalls inside the bed with thick plastic sheeting. Drill holes into timbers every 4 feet as you build the bed walls so that you can drive rebar through the top to a depth in the soil equal to the height of the wall.
If you use dimensional lumber such as 2x8's to build the side walls with you will need to use decay-resistant wood stakes to hold the wall in place. Attach the stakes with screws to the inside of the wall and they will not be noticed.
For a unique-looking raised bed cut landscape timbers off at a length of 2-4' and set the posts vertically in the ground, half buried and half above the ground.
Modern wall blocks are also great for use to build raised beds. Wall blocks will cost more, but last much longer. Make sure that the blocks you use are interlocking and suitable for use at the height you want to build to.
After building your raised bed walls and have backfilled with the soil mixture you are ready to plant. Below is a listing of vegetables that perform well in Zone 8.
