How to Make Flower Pots With Portland Cement, Peat Moss, & Fibers

Make stylish concrete-type planters that are very strong but lightweight.

Prior to the 1800s alpine dwellers used a volcanic rock known as tufa to carve sturdy but lightweight watering troughs and planters for the farm. You can make your own flowerpots that resemble tufa from a mixture called hypertufa, which consists of Portland cement, perlite, peat moss and reinforcing fibers. Using ingredients easily found at home improvement centers, you can easily create sets of unique, matching lightweight planters that withstand weather extremes.

Things You'll Need

• Inner and outer molds
• Plastic trash bag
• Portland cement
• Peat moss
• Perlite
• Synthetic concrete reinforcing fibers
• Water
• Wheelbarrow
• Screen
• Small shovel
• Wooden dowels
• Wire brush
• Rubber gloves
• Dust mask
• Plastic sheet

Instructions

1. Find an outer mold for your flowerpot. It can be anything from a dishpan to a cardboard box. You can use any container that is sturdy enough to maintain its shape until the hypertufa dries. Also find an inner mold that is slightly smaller than the outer mold. It should leave about two inches between all sides when nested into the outer mold. Other mold container ideas include wooden crates, other flower pots, trash cans, cake pans, and plastic food storage tubs. The possibilities are endless, so use your imagination. Line your mold pieces with a plastic trash bag, making sure it fits into all the corners and recesses of the molds.

2. Sift the peat moss through the screen to remove all large pieces. Mix equal parts of the Portland cement, peat moss and perlite in a wheelbarrow, tub or other sturdy container, and mix with a shovel. Add a few ounces of the reinforcing fibers, no more than a handful. Use a folding motion to thoroughly mix the dry ingredients.

3. Add a little water at a time, mixing between additions, until a handful of the hypertufa holds together. Think mud pies. If water freely runs out or the mixture is runny, add more of the dry ingredients in equal parts. The mixture should be easy to sculpt. You will not have to add more fibers.

4. Press the mixture into the bottom of your mold, laying down a 2- to 3-inch layer. Do this a handful at a time, making sure the bottom is evenly covered with the wet mix.

5. Put the inner mold into a plastic trash bag, which will serve as a liner, and press the plastic-covered mold into the bottom layer. Keeping the plastic smooth, pack the gap between molds with the hypertufa mixture. The gaps that will be the sides of your flowerpot should also be two to three inches thick. Make sure to pack the sides well and not leave any air holes. Level the top edge of the hypertufa when the sides are done. You can also poke holes in the top edge with your finger or other tool after it is level to create an interesting design.

6. Position wooden dowels in the bottom of the wet hypertufa to make drainage holes for your flowerpot. If you have an inner mold, you will have to make holes in it for this purpose. Alternatively, you can drill holes with a masonry bit after it is dry .

7. Cover with plastic and allow it to cure for 14 hours. At this point test the hardness. If you can scratch the surface with your fingernail, it is still too soft. Retest every few hours until it is too hard to scratch with your fingernail.

8. Remove your flowerpot from the mold. Brush it with the wire brush to smooth the corners, top edge and all surfaces. You can use the wire brush to texturize it as well, but be careful not to press too hard.

9. Allow the flowerpot to cure in a shady spot for another three weeks and you are ready to use it.

Tips & Warnings

• Buy straight Portland cement, not pre-mixed concrete or mortar.

• You can find synthetic concrete reinforcing fibers at most masonry-supply stores or online.

• Use plastic trash bags that do not have bunched ends to line the molds. The wrinkles in the bag will translate into wrinkles in your flowerpot. Use trash bags with smooth seams.

• The larger your flowerpot, the thicker the walls should be. Very small pots can be as thin as one inch; otherwise, two or three inches is best.

• Pack the wet mixture around the outside of a mold instead of inside it, then sculpt interesting shapes on the outside. You can also press moss, leaves, marbles or pieces of mirror into the wet hypertufa for interest. Make sure to level the bottom of the pot and make drainage holes before the mixture starts to dry.

• Wear rubber gloves and a dust mask to keep the ingredients from harming your skin or airways.

References

• Fine Gardening: Helen Dawson

Resources

• University of Nebraska-Lincoln Extension: Backyard Farmer - Hyper-Tufa Containers