Make troughs for the garden

Hilary Nichols, a rock garden specialist and senior horticulturist for the Atlanta Botanical Garden, teaches classes there in making troughs. She says the idea for troughs as garden containers came from the English, who used old stone sinks or feeding troughs for their alpine plants. True stone containers became difficult to find, so gardeners sought a man-made solution.

“Hypertufa was created to give alpine plants the same type container they would thrive in, with sharp porous drainage, but not as heavy or expensive as the original stone containers,” Nichols said.

Carole Teja, a Gwinnett County Master Gardener, first saw troughs for sale about 10 years ago and balked at the prices. She realized she could make her own far less expensively. Now she makes troughs every year for her garden, as gifts for friends or to use as door prizes for the many organizations she’s a part of.

She recently volunteered to teach fellow Georgia Perennial Plant Association member John Wolfinger to make his own hypertufa trough.

“Whatever you use, you’ll ruin,” Teja said, so she advised wearing old clothes and covering the ground and any tables with a sturdy drop cloth to contain the mess.

Making a trough requires a mold. It can be something as simple as a cardboard box or a disposable foam cooler with another box or container that fits inside. Or the trough can be molded on the outside of any container that’s been covered with plastic to make it waterproof. At the botanical garden, they double plastic grocery sacks, fill them with sand, knot them and turn the bags knot-side down to create an oval or round surface to use as a form.

Teja’s recipe for hypertufa is one part Portland cement, one part peat moss and one part perlite. The botanical garden uses a mixture of one part cement to three parts total of the moss and perlite. Both recipes will work, and there are many more.

Teja and Wolfinger poured the ingredients into a plastic mixing tub, being careful to avoid the dust from the cement. A face mask is a good idea, and gloves are necessary to protect hands from the caustic cement slurry. After making sure everything was well mixed, Teja added water from a watering can, giving her more control than using a garden hose.

For a mixture that will go on the outside of a mold, the botanical garden’s Nichols suggests looking for a consistency that crumbles in your hands like soil but when squeezed releases a tiny bit of water. She instructs her students to grab a handful of the mix and start building their troughs from the base up.

“Be very rough,” she said. “The harder and more you pound on your trough, the better the materials will stick together.”

Although hypertufa is porous, the trough will still need drainage holes. Dowels, short lengths of PVC pipe or small plastic cups can be used for the holes and then removed as the trough cures.

Every part of the trough must be thick enough to hold up when it’s dry. A nail dipped in paint to the 1- or 2-inch mark makes an inexpensive gauge to ensure that the trough sides are the right thickness.

For a box-inside-a-box mold, the mixture can be much wetter. After achieving the right consistency, Teja poured in enough mix to make a bottom at least an inch thick, added drainage holes and set the smaller box inside. Weighting the box with sand, Wolfinger poured in the mix to fill up the sides.

The finished trough was covered with a plastic sheet to keep the mixture moist while it cured. Depending on how wet the mixture is, curing can take several days to a week.

Removing the mold before the trough is completely dry gives time to clean up the exterior and remove any rough parts while the exterior is still a little plastic.

Hypertufa troughs are full of lime from the cement, so they can’t be planted right away. Nichols recommends washing the trough with a mixture of one part vinegar to nine parts water to remove the lime.

Once that’s done, the trough is ready to be planted, but beware that this grown-up version of making mud pies can be highly addictive. You might find yourself, like Teja, expanding your hypertufa empire each year.