Cement planters are a durable choice for plants that remain outdoors year round such as containerized ornamental trees for decks and patios. The thick surfaces of the cement planter insulates the roots of the plant against freezing in winter and baking in summer. Cement planters may be made lightweight by mixing the cement with aggregates and loam to create hypertufa, a synthetic stone that takes the place of alpine rock. Building hypertufa planters is simple.
Create a mold by using nesting cardboard boxes. The smaller box should be 2 inches smaller in length, width and height in order to create a planter that is 2 inches thick. If you create a mold from wood, you must line the mold with plastic. Otherwise the hypertufa will stick and become damaged when you try to pull it apart.
Pull on rubber gloves before mixing your hypertufa. Cement is caustic and can cause irritation if it comes in contact with your skin. You may also wish to use a breathing mask to avoid breathing cement dust.
Mix a hypertufa mix by combining equal measures of cement, sand, reinforcing fibers and peat moss in a 5 gallon plastic bucket. Add water to the bucket and mix with a trowel until the hypertufa is the consistency of cake batter.
Stand a piece of three-fourths-inch PVC pipe that is 2 inches long on its end in the center of the large box. This will form the drain hole. Hand-pack the hypertufa mixture around the pipe until it fills the bottom of the box to a depth of 2 inches.
Place the second box inside the first box onto the surface of the hypertufa and the PVC pipe. Pack hypertufa into the space between the two boxes.
Mist the two boxes with a spray bottle and cover with a dry cleaning bag for 36 hours so that the mixture can cure. If the mixture can be scratched with your fingernail, it is not done curing.
Remove the mold and smooth over the planter with a wire brush. Then leave the planter in a shady spot for three weeks to finish curing.