Cement planters are durable, attractive additions to a porch, patio, rooftop garden or deck. The stone protects tender plants from freezing in winter or being blown over by wind year-round. Although cement planters may cost a considerable amount, you can create one at home for far less than the purchase price. Some manufacturers make cement molds for casting projects. You can also create your own casting form by hollowing out sand or using plywood.
Measure, mark and cut the ¾-inch plywood into two pieces that are 18 inches long and 10 inches wide. Cut two additional pieces that are 15 inches long and 10 inches wide. These will make the sides of the mold for the planter.
Measure, mark and cut the 1 1/2-inch plywood into a piece that is 20 by 17 inches. This will be the bottom of the mold form.
Cut a groove into one side of each end of the 18-by-10 inch plywood pieces. The grooves should be located 1 inch from the end of the plywood and should be ¾ inch wide by ¾ inch deep.
Fit the ends of the 15-by-10 inch pieces into the grooves of the 18-by-10 inch pieces. Wrap the exterior of the box with a bungee cord to secure it.
Center the box over the 20-by-17 inch bottom piece. Trace around the interior and exterior walls of the box. Remove the box and cut grooves into the bottom piece between the marked lines. The grooves should be ¾ inch wide by ¾ inches deep.
Fit the wooden box into the grooves. This will be the mold for your container. Drill a hole into the center of the bottom piece. Rub oil over a piece of dowel rod about 2 inches long and insert it into the hole to create a drainage hole for your container.
Fill a cardboard box that is about 15-by-12 inches wide and 8 inches deep with play sand. Coat the exterior of the box and the interior of the wooden form with oil.
Mix equal parts sand and cement in a bucket with water until the mix is the consistency of cake batter. Add cement dye if you choose to make your planter a specific color. Stir in a handful of concrete reinforcing fibers. Pour the mix into the bottom of your mold until it is flush with the top of the dowel rod.
Place the box onto the surface of the poured cement and center it so that the space between the box and the plywood walls is equal. Pour cement into the space between the box and the walls. Tamp down the cement with a tamping tool such as a plastic stirring rod to remove air pockets from the box.
When the concrete has set, remove the mold and cardboard box. Mist the planter with a spray bottle and cover with a plastic dry cleaning bag. Allow the planter to harden and cure for 48 hours. Brush the sides with a copper bristled brush to remove any rough edges.