Known for fewer weeds, warmer soil and ease of use, many gardeners choose to build raised garden beds for flowers, herbs and vegetables. While there are several raised-bed systems on the market that can cost hundreds of dollars, it's cheap to build a sturdy bed with cement blocks. When cement blocks are properly placed in a good location, your raised bed can last a lifetime.
Measure out the size of the bed you want to build and place wooden stakes into the ground at each corner. The full size of your bed in inches needs to be divisible by 16 for the blocks to fit in the space you mark off.
Run string around the perimeter of the bed, looping around the corner stakes, or spray a landscaping spray from stake to stake to mark off the bed. Remove the upper sod layer from the ground, if necessary. Dig the soil inside the perimeter and remove the top 4 inches from the surface.
Make the ground as level as possible; if working on a hill, you will need to dig deeper as you work the ground on the slope. Set up a base layer of cement blocks to form the foundation of the bed; set the blocks with the holes facing up and run them around the entire perimeter of the bed.
Build the second layer of blocks over the first, but offset the blocks like bricks so each block on the second row rests on two blocks from the first row. Build a third and any other rows with the same offset until your bed is the desired height.
Place a piece of rebar cut to a foot longer than the height of your raised bed through the holes of the blocks at each corner. Use the rubber mallet to drive the rebar into the ground until it is level with the top of the bed. Fill each set of holes along the sides of the bed with gravel, covering over the rebar on the corners.
Fill the body of the raised garden bed with a three-part mixture of aged manure, loam and compost, or with a garden soil from your local garden center. Fill the bed up to an inch from the top and smooth it out to make it level.