Let it Rock with Hypertufa Troughs

These containers are great for showing off alpine rock garden plants, succulents, dwarf hostas, dwarf conifers, bonsai, sedums etc. Making hypertufa is easy and fun. It’s best done outdoors as the dry ingredients are very dusty. A dust mask and gloves are recommended.

Whereas tufa is a naturally occurring porous limestone, hypertufa is an artificial stone material used to make garden planters. Alpine gardeners originally used antique animal watering troughs, which became rare and expensive, so “hypertufa” was developed.

Supplies

• Mixing tub (mortar tub);
• Sphagnum peat moss (sieved to remove large chunks or stems);
• Perlite;
• Portland cement;
• Concrete reinforcing fibers (optional for large planters);
• Water;
• Container for measuring dry matter (coffee can, bucket, measuring cup, etc.);
• Dust mask;
• Rubber/nitrile gloves;
• Mixing trowel;
• Plastic sheeting (optional if outdoors);
• Plastic, metal, cardboard or wooden container for mold;
• Wire brush for scratching the surface as the project dries (optional);
• Adhesive tape to reinforce flexible shapes (cardboard);
• A small plastic garbage bag to line the formwork for easy removal.

Recipe

There are many recipes for tufa , but I have settled on the 1-1-1/2 mix: one part peat (sifted), part 1 perlite and 1/2 part Portland cement. You can add color by mixing in pigments as you become more comfortable with the project. There are concrete dyes and stains available. I enjoy when moss starts to cover the trough for an aged look.

Procedure

While wearing a dust mask and gloves, mix one part perlite and one part screened peat. Blend together. Be sure to remove sticks from the peat. They can weaken the finished container. Add half a part Portland cement and blend all dry ingredients thoroughly. Make a “volcano” in the middle of the mixing tub and SLOWLY add water. Mix with gloved hands or use tools. Add more water if the mix is too dry. Keep mixing. You are looking for the consistency of a brownie mix. DO NOT ADD TOO MUCH WATER, or you will have to adjust the dry ingredients. Keep mixing until you can squeeze a handful of mix and it will only ooze 2 to 3 drops of water.

Don’t Rush!

Let stand for about 10 minutes for the peat to absorb the water. It will not harden during this time. Simply pack hypertufa mix around your container, or mold it on the inside of a container. Fill your container with the wet mix and form it up the sides and bottom to 1 ½ – 2 inches in thickness. I like to pat down the mix until it becomes smooth and kind of shiny. That’s getting the air bubbles out. Remember to leave space for soil by digging out the middle or use a pot or bowl to form that space. A putty knife or a trowel is great for scooping out the middle. You can add corks, dowels or short two-inch PVC pieces to push in the bottom for holes (for drainage). Remove later.

Drainage Tips

You can add corks, dowels or short two-inch PVC pieces to push in the bottom for holes (for drainage). Remove later. You can also drill several holes in the bottom of the container after 48 hours. The trough will be solid but can be easily drilled. Before adding soil, cut a piece of landscape fabric to cover the holes in the bottom of the trough to keep critters out and soil in.

Objects to Be Used for Forms

You can mold inside a container, or over the outside. A large plastic planter bowl makes a great project, either filling the bowl with a 1 ½ to 2-inch thickness tufa mixture or turning the bowl over and adding the mix to the outside. If using the outside technique, be sure to make a flat, level bottom so the bowl will sit properly. Always leave room inside the project for adding soil to the finished container. Smaller pots with small soil-holding spaces dry out sooner. Try using nursery pots, a large stainless steel or plastic mixing bowl or planter bowl; cardboard boxes (reinforce outside with duct tape); Insulation blue board for larger troughs (make into box with screws and duct tape). Check craft store, junk shops, etc. for baskets, bowls etc.

If desired use a nail or screwdriver for etching a pattern on the sides when your project is released from the mold (usually 24-48 hours). Use a drill and ½ inch bit to drill several holes in the bottom after releasing from mold. No time limit on this.  

Experiment!

 If you have mix left over, experiment! I like to fill the four-packs that plants come in to make feet for the planters. Or half gallon milk cartons cut in half. Just carve out space for soil. It’s a good idea to cover your project with plastic so the troughs don’t dry too fast. Do not put in sun! After 48 hours, the tufa can be popped out of the mold. You can leave it outside to weather (leave indoors if making in Winter).

Use the wire brush to smooth the surface if desired, or use a nail or screwdriver to scratch a pattern in the stone. Plant the tubs with a blend of good potting soil and a gritty cactus mix soil. It’s a good idea to let them weather for a few weeks or more to leach out the lime in the Portland cement, which can leave a gray film on your deck. You can wait to plant or plant sooner. Experiment and enjoy!. Warning: hypertufa is slightly addicting!

Use half and half good potting soil and a coarse mix such as Black Gold Cactus Mix. Great for succulents and alpine plants. Top-dress with pea gravel or other grit after planting for a finished look. I have used aquarium gravel for smaller pots.

The North American Rock Garden Society has a booklet called Handbook on Troughs that you will find useful for learning more on planting troughs. https://www.nargs.org/