Rock gardens rock. But having to lug a ton of rocks around your garden? That part doesn't. But don't give up on the idea just yet. You can lighten your load by DIYing the "rocks" yourself using hypertufa (a cement aggregate that mimics tufa -- a type of limestone) and lightweight materials like styrofoam, plastic, or paper. What's more, it's super easy and fun. Ready? Let's rock!
Things You'll Need
- Portland cement
- Sphagnum peat moss
- Bulky lightweight materials such as styrofoam (our recommendation), empty plastic bottles, balled-up pieces of newspaper, cardboard boxes, etc.
- Chicken wire
- Protective heavy-duty work gloves (for handling chicken wire)
- Rubber or latex gloves (for handling hypertufa mix)
- Cutting pliers
- Garden trowel (optional)
Step 1: Make Rock Form
To make the rock form, you'll need to securely bundle up whatever lightweight material you'll be using inside of chicken wire. If using styrofoam, break it apart into manageable pieces, then group them together to form the basic rock shape you'd like. If using plastic bottles, we recommend wrapping them together with duct tape before bundling up with chicken wire for easier handling. If using newspaper, ball them up for increased bulk.
Cut a piece of chicken wire large enough to completely cover your bundle with some overlap. Then, wrap it all up in the wire, as shown below, bending the overlapping edges inward to hook and secure your chicken wire into place. Make sure to use protective work gloves when handling the chicken wire, as the cut edges will be sharp.
Step 2: Make Hypertufa Mix
The hypertufa mix we'll be using consists of 1 part portland cement to 1 1/2 part sphagnum peat moss to 1 1/2 part perlite. How much you'll make depends on how large your rock form is. For this particular rock shown, 1 part = 2 quarts, and the finished piece measures 12 x 10 x 8 inches. Don't stress about mixing enough hypertufa to begin with, as you'll be able to mix more as needed while you work.
Add the cement, moss, and perlite into a large container and combine well. Gloved hands are the best for the job.
Add a bit of water (about half a cup) and mix thoroughly to make sure that all of the contents have been evenly moistened.
At this stage in the mixing process, it's helpful to use a garden trowel to scoop up and turn over the dry mix at the bottom to make sure that it gets incorporated.
Continue adding water in small increments and mix with your gloved hands until it easily clumps together in a ball as shown below. Take care not to add to much water as you don't want it to be too thin nor dripping wet.
The finished consistency should be easily packed together but still a bit on the crumbly side.
Step 3: Pack Hypertufa Onto Rock Form
Now the fun part! Tightly pack your wet hypertufa mix all over your entire rock form and making sure that no stray pieces of chicken wire are poking through.
Compress it as best you to can to ensure that the hypertufa won't fall off your form while setting.
Once the top part is covered, turn it onto its side and cover the bottom (see tip below). If some of the top pieces of hypertufa fall off while turning it, simply pack it back on.
Note that your rock will be totally flat on the bottom which, needless to say, isn't very realistic. If you plan on leaving the finished rock in this position (flat side down) permanently, this shouldn't make a difference. However, if you're set on having the entire surface appear rock-like, don't apply hypertufa to the bottom of your form just yet. Complete the rest of this tutorial first for the top portion of your rock. Once the top portion has been shaped and set, repeat the entire process for the bottom portion of your rock.
Step 4: Shape Your Rock Surface
Rock form completely covered? Great! Now it's time to get artistic. There are many ways to give your rock a more organic look, but we'll describe two easy methods.
One is to use your fingertips to create little dimples on the surface as shown.
Another method is to create creases using the edge of a garden trowel or other straight-edged tool.
I encourage you to check out some real rocks for ideas on how to make your faux rock appear as realistic as possible.
Step 5: Wait Until Set
Once the rock has been shaped to your liking, it's time to wait at least 48 hours to allow it to set. I like to let them sit in a shady spot outdoors. Allowing it to dry too quickly in full sunlight may compromise the structural integrity of your rock.
Step 6: Brush Off
After 48 hours, your rock should be all set and ready to place in your garden! Before doing so, use a firm-bristled cleaning brush to remove any loose dust or pieces of perlite off the surface. In addition to brushing off, you can also spray it down with a garden hose if you'd like.
You'll notice that your rock will lighten in color (as well as weight) after setting. It will continue to lighten in color considerably after being placed outdoors. To maintain a dark appearance or to tint your rocks specific colors, add the appropriate cement/concrete colorant(s) to your hypertufa mix.
Line them up to create flower bed borders, nestle them among succulents -- whatever rocks your world. (Sorry, couldn't resist.)