How to Build Concrete Block Raised Planters

Choose a site for the first raised planter. Select a bright, sunny and level site with good air movement. Measure out the garden according to your needs; vegetables do well in 2- to 3-foot-wide gardens while large shrubs such as roses need larger 10- to 20-foot-square plots. Calculate border lengths to accommodate a set number of concrete blocks to avoid having to break the blocks.

Dig a trench around the borders of the raised garden 3 inches deep and wide enough to fit the blocks. Keep the trench at an even depth around the garden to keep the wall even.

Lay the first layer, or course, of blocks in the trench. Fit them end-to-end for tight seams, with the solid sides facing outward and the holed sides facing up and down.

Mix quick-set concrete in a bucket, per the directions on the package. Use a trowel to transfer concrete into the holes of the concrete blocks. Fill each hole three-quarters full to add security to the wall.

Put a second course of concrete blocks on the first. Start each side with the first block centered over the first seam in the bottom course to stagger the seams for better security. When you reach the end of the wall, turn the last block so it sits on the corner, with half on the end of the first side of wall and half on the second side of the wall. Repeat the concrete step with the second course of blocks. Finish the wall with this course or add a third course, according to personal preferences. Allow the concrete to set overnight.

Fill the garden with a mixture of 50 percent organic compost and 50 percent topsoil or garden loam. This loose, nutritious mixture gives plants a good base for growing. Turn 10-10-10, 13-13-13 or 5-10-10 fertilizer into the soil, per manufacturer directions, for starting nutrition.