Hypertufa is a method of creating garden troughs, pots and containers that mimic the look of tufa, an alpine stone. Hypertufa mixtures are made of organic materials such as peat moss, which decompose and leave behind a porous texture much like tufa stone. There is no one correct recipe or method for making hypertufa, although if you wish to create a hypertufa container that looks as good as it possibly can, there are certain steps that experts say that you should follow.
Choose a simple container design if you have never made a hypertufa container before. According to The Artistic Garden, a simple container design such as a trough or square pot made by sandwiching hypertufa between two boxes will yield the best results if you have never tried to cast a hypertufa container before.
Obtain two cardboard boxes for your hypertufa moulds. The smaller box should nest within the larger one with several inches between the two to create a hypertufa container that is several inches thick. The website Fine Gardening advises against using wood or metal containers because the hypertufa will stick to the mould unless you line it with plastic.
Mix together 1 part Portland cement, 1 part peat moss and 1 part perlite in a wheelbarrow or plastic bucket. Add water from a garden hose until the mixture is the consistency of a mud pie. According to The Artistic Garden, this is a basic hypertufa mixture that is best for any beginner. As your experience with creating hypertufa grows, you can vary your mixture according to your personal preference.
Place the 2-inch-long piece of PVC pipe in the centre of the largest box. This will become the drainage hole of your hypertufa container.
Pack the hypertufa mixture into the bottom of the container around the PVC.
Place the smaller box on top of the hypertufa mixture.
Pack the remaining hypertufa mixture into the space between the two box walls.
Spray the hypertufa and the cardboard boxes evenly with water from a garden hose until the boxes are saturated with water. The presence of water helps the concrete harden to a stronger consistency as it dries.
Cover the mould with a plastic tarp and allow it to set for one week in warm weather. According to Washington State University, the best temperature to cure hypertufa in is over 12.8 degrees Celsius. Never allow hypertufa to freeze. If you are trying to cure hypertufa at temperatures between 4.44 and 12.7 degrees C, allow the mixture to take up to two weeks to set.
Peel the cardboard boxes away from the inner and outer sides of the container.
Brush the container with a wire brush to smooth out the surface and give it a weathered appearance.
Spray the hypertufa container with water until the surface of the container is dark with moisture. Cover the container with plastic and allow it to cure and harden for another two weeks.
Uncover the container and spray it consistently for 5 to 10 days to allow the water to leech out alkalinity. Spray the container until it is coated with water. Allow the water to drain away and the surface to dry before spraying it again. This will help to keep plants that grow inside of the container from being affected by the alkaline cement in the container. Alternatively, you can simply leave the container under a steady stream of water, such as a dripping faucet.
Mix 1/4 cup vinegar to 1 gallon water in a large washing tub. Submerge the hypertufa container in the tub filled with vinegar solution to neutralise its alkaline surfaces. The container should be ready for planting after this point.
Cement is caustic and can harm you if left on your skin or inhaled. Always take protective precautions, including wearing long, rubber gloves, a plastic apron, safety goggles and breathing protection, when working with cement. For large hypertufa containers, add 1 cup of reinforcing fibres to the mixture to improve the strength of the container.