If you have a secret hankering to join in whenever the kids make mud pies, you'll love creating your own stone flower planter box from a material called hypertufa. Similar in weight to the light, porous volcanic rock known as tuff, hypertufa is made from cement, peatmoss and a third ingredient such as sand, perlite, vermiculite or coconut fiber, each of which gives the final product a slightly different quality and finish. Stone planters made from hypertufa are lighter than the real thing and provide better drainage. You can plant directly into them, and leave the plants in place for five to 10 years.
Sieve the peatmoss to remove any sticks or lumps.
Put on rubber gloves and a dust mask, and mix 1 part Portland cement, 1 part sand or perlite and 2 parts peatmoss in a wheelbarrow or large plastic container. Planters made with sand are more durable but planters with perlite are lighter. Perlite can irritate lungs, so keep the dust mask on while working with it in a ventilated space.
Add 1 part water and mix in well. Add more water if necessary until you achieve a sticky consistency similar to cottage cheese.
Spread a 1- to 2-inch layer of hypertufa mixture on the bottom of a large cardboard box. Place a smaller box inside. Center the small box so that the gap between the two box walls measures the same all around. Pack hypertufa into the gap to the brim, and smooth it off. Alternatively, turn an earthenware container upside down and cover it in hypertufa, working from the ground up. Make the top smooth and level because this will be the base of your planter. Squeeze out air bubbles as you go.
Cover the mold filled with hypertufa with a plastic sheet and leave it to cure for 36 hours. Scratch a small area of hypertufa with a screwdriver or knife. If it doesn't leave a mark, remove the plastic sheet and mold. If the hypertufa is still soft, check again every four or five hours.
Leave your new stone planter in a shady place outdoors for three weeks to finish curing. If the weather is dry, spray it with water two or three times a day.
Smooth off any sharp edges or protruding areas with a stiff wire brush. Scrub the surface to create an aged, roughened effect, if desired.
Fill your planter with water and let it drain, doing this repeatedly for 10 days to remove alkalinity from the cement. Mix a solution of 3/4 cup of vinegar in 1 gallon of water, use this to rinse the planter before filling it with soil and plants.