If you want to evoke a blank stare, tell someone you are making a hypertufa grot.

Alternate reactions are, “Gesundheit,” or “Sounds like a personal problem to me.”

Hypertufa is imitation tufa, a rock-like calcium carbonate deposit. Hypertufa is made of varying combinations of cement, perlite, peat, sand and/or other organic materials. The result is a porous, imitation stone which is a bit lighter than concrete and can be molded into planters, troughs, and sculptural shapes. One of these sculptural shapes is called a grot, from grotesque, and is a humanlike shape that may seem to be peering up through the ground.

Why make grots?

If you have to ask. . .

Here’s what I put together:

1 part portland cement
1 1/2 parts coir
1 1/2 parts perlite

optional: reinforcing fibers for concrete
water

See the links at the bottom of this post to many more hypertufa recipes and instructions that you should rely on more than mine. I am a rank beginner.

Pictured above are the basic building blocks of hypertufa grots.

• plastic nursery pot lined with a plastic supermarket grocery bag
• watering can full of water. (See my handy device to let me know when the can is full? Okay, somebody stuffed a handball in there and I can’t get it out.)
• dry portland cement
• a bucket of reconstituted coir. I am using coir instead of the traditional peat because it is a renewable resource. The “brick” perched on the edge of the bucket is compressed coir–the coir in the bucket is one brick plus enough water to make it fluffy. Some hypertufa folks insist unless the mix contains peat it isn’t genuine imitation tufa. Until the International Hypertufa Committee makes a ruling, I will continue to call the coir version “hypertufa”.
• bag of perlite and a can of cooking spray. Ignore the cooking spray. I had intended to use it as a release agent, but since I turned the grots out of the forms before they were completely set I didn’t need it.
• On the far left if you look closely you can see a dust mask which I needed when working with the dry cement–not something you want to breathe. I also used rubber gloves. Cement is caustic.

Step 1: Mix up the cement, peat/coir, perlite.

Step 2: Add water in small amounts until you have a homogeneous mud–not too wet, not too dry. Not crumbly, not soupy, just sort of plastic and clay-like.

Step 3: Shovel mix into your prepared containers and tamp down with a scrap of wood.

Until it looks like this:

Step 4: Cover with another plastic bag and leave for 24 hours.

Step 5: The next day, uncover and turn out onto a work surface. I used my wheelbarrow and some newspapers. The grot will be somewhat set up but not altogether firm. Unmold carefully.

Step 6: With a knife or a trowel, round off the top to make a head shape. You may get as creative as you like here.

Step 7: Recover and leave another 24 hours.

Step 8: The next day, mix up a small amount of cement with a bit of water. I found that a slightly drier mix worked better–a tiny bit crumbly in the bucket, but claylike when kneaded in the hand.

Step 10: Using your imagination, apply features such as brows, nose, eye mounds, and ears. I pressed firmly and feathered the edges with my gloved hands to make the join as seamless as possible. Press a marble or stone in the eye mounds, making sure they are well inset and that the cement partially covers the marbles so they won’t fall out. I only had regular marbles, but the larger shooters would have been better.

I think this one looks like an owl with ears.

Once you are satisfied with your face, lightly cover again and allow to set up for a few days until the grots seem cured enough to move into the garden. They will continue to harden.

A slurry of moss and buttermilk or yogurt will encourage moss growth, or a watery solution of acrylic paint will help them to blend into the environment.

According to the hypertufa guru of Efil Doog in New Zealand, the apparent epicenter of grots:

“Grots inhabit only dark forest floors and gloomy garden corners. They are quite deficient in social skills. It is best not to disturb them.”

Good places to find information about grots and hypertufa:

A book on creating Hypertufa Containers

GardenWeb Hypertufa Forum
Dave’s Garden Hypertufa and Concrete D
iscussion Forum
The Artistic Garden
Fine Gardening
Timpyworks