Cement planters are a practical container for rooftop and patio gardens as well as for trees or other large container plants that are impractical to bring indoors. The sturdiness and thickness of a cement planter insulates the contents from high winds and from freezing at the root line due to winter cold. One easy way to construct lightweight cement planters is to cast them in cement. Hypertufa is a lightweight cement mix that gives planters an aged stone look.
Create a cement planter mold by digging a pit in the soil and filling it with sand. The sand in your mold should be 2 inches wider and deeper than a plastic waste basket.
Place the waste basket into the hole and compact the sand by leaning all of your weight onto the waste basket and twisting it.
Cover a 2-inch diameter, 3-inch-long piece of dowel rod in vegetable oil. Insert the dowel rod 1 inch deep into the sand at the center of the hole.
Mix a cement mix that contains 2 parts peat moss, 1 part cement and 1 part perlite. Mix with water until the mixture is the consistency of a mud pie.
Pack the cement around the bottom of the mold to a depth of 2 inches. The mix will be level with the dowel rod.
Insert a cement reinforcing tube into the center of the hole. Center the tube inside the hole.
Pack cement around the space between the tube and the walls of the hole. Spray the tube and the hole with water and cover with plastic sheeting. Allow the cement to dry up to four days.
Reach into the sand and pull the planter out of the sand. Push the dowel out of the bottom of the planter. Grasp the tube and pull outward while twisting to free it of the cement. Be very careful not to break the cement planter. It will still be brittle at this point.
Brush the planter's surfaces with a copper bristled brush to smooth the rough edges. Place the planter aside to allow it to harden and cure for another two weeks before planting.