(Whether you're starting your first garden or switching to organic, Rodale’s Basic Organic Gardening has all the answers and advice you need—get your copy today!)
WHAT CAN GARDENERS MAKE OUT OF HYPERTUFA?
Lots of things! The rock that forms during this process is lighter, more porous, and less likely to be damaged by freezing than typical concrete is—making it a great choice for pots, planters, fake rocks, and garden ornaments. That being said, hypertufa is also weaker and less wear-resistant than typical concrete, so it's not a particularly good choice for stepping stones that will get a lot of traffic or walls and supports that need to hold a lot of weight. And, being porous, it isn’t a good choice for birdbath basins or ponds.
Related: Make Your Own Upside-Down Tomato Planter
HOW TO MAKE A HYPERTUFA POT
A pot is a classic starter project for working with hypertufa—you can gift your finished product, or just keep your pot for your own use!
Gather Your Tools And Materials
To make a pot, you'll need:
- A mold
- Mixing container—a plastic pail or a dishpan will work for small projects; for larger projects, a wheelbarrow or inexpensive mortar mixing pan is perfect
- Heavy spoon or trowel
- Plastic trash bag or tarp to cover the project while it cures
- Rubber dishwashing gloves
- Dust mask
- Optional: A coarse sieve or piece of ¼” wire mesh for sifting the peat moss and stiff wire brush for smoothing rough edges.
- Portland cement (NOT pre-mixed concrete or mortar)
- Perlite OR Vermiculite
- Peat moss OR the more environmentally-friendly coir
- Optional: Synthetic concrete reinforcing fibers OR straw (these add strength for very large projects)
- Optional: Concrete colorant (if a pale browny-gray pot doesn’t appeal to you)
You have a few options for your mold: the simplest is just two cardboard boxes, one enough smaller than the other so that there is a 1” to 2” space all around the smaller one when you nest it inside the larger one. Another option is to use two plastic nursery pots—pick ones that are thin and flexible so you will be able to cut and remove them once the hypertufa hardens. You can also craft a hypertufa pot freehand over a shaped mound of moist soil covered in plastic, but a mold made from two boxes or pots is easier for most people to start with.
Related: How To Build A Simple Raised Bed
Set Up Your Pot-Making Space
Set up a place to work where you can be a bit messy, protecting surfaces with tarps. If you work outdoors, pick a shady area—sunshine may make your pot harden too fast, increasing the risk of cracking. If outdoor temps will be less than 45°F over the next day or so, you will need to work indoors. In cooler temperatures, the concrete doesn’t harden as well and your pot may crumble or fail prematurely.
When it comes to hypertufa, exact proportions are not critical, so don’t obsess over them.
- 2 parts (by volume) portland cement
- 3 parts (by volume) perlite
- 3 parts (by volume) sifted peat
- Water (more on how much later)
How much to buy:
This, of course, depends on the size of your project. A large pot might take about 12 pounds (about 1⅓ gallons) of dry Portland cement and about 2 gallons each of perlite and peat.
Related: How To Grow Eggplants In A Pot
Hypertufa mix doesn't harden instantly, but you can't mix it and set it aside for hours either. When you've gathered up all your materials and supplies, and are ready to form your pot, here's what to do:
1. Put on rubber dishwashing gloves and a dust mask as protection—cement can burn your skin and neither perlite dust nor powdered cement are lung-friendly.
2. Place your peat into your mixing container, pick out any large sticks, and break up any lumps (or sift it).
3. Add your other dry ingredients and mix thoroughly. (Follow label directions for adding colorant.)
4. Add water, a little at a time, and mix it in well until everything is just barely moist and crumbly. You have added enough water when a ball you make between your gloved hands holds together when you squeeze it. Be careful not to make your mix too soupy, as excess water makes for a weak finished product that may fail prematurely.
5. Press a 1" to 2" thick layer of your mix firmly into the bottom of your larger box. Then center the smaller box on top of that and firmly press handfuls of mix into the space between the boxes' sides until you get to the height you want. Level and shape the top of the moist mix as desired.
6. Rinse your gloves, tools, and mixing container immediately with water to remove anything that would otherwise harden onto them. Avoid putting solids down any drain! Scrape them into the trash or let them harden on a sheet of plastic before discarding.
Cover your project with a tarp or plastic bag and let it sit undisturbed for 24 to 36 hours. Then test to see how hard it is—if you can scratch the surface with a screwdriver, re-cover it and check again after 12 hours or so.
Once you can’t scratch the surface, carefully tear or cut away the inner and outer molds. If desired, now is the time to round or smooth sharp edges and texturize the surface with a wire brush or trowel. Work gently, as the center of your hypertufa is still softer than the surface.
Leave your finished pot undisturbed in a shady location for three weeks to allow it to harden completely.
At the end of the three weeks, you need to soak it in a tub of water or run water over it repeatedly for a week or so to remove any residual free lime, as lime is very alkaline and will harm most plants. Leaving your pot outside in the weather for a few months works, too, if you get regular rains.