how to make hypertufa recipe for trough gardening

June 2011

How to Make a Hypertufa Trough

Leonard J. Buck Garden, Far Hills, NJ
The Leonard J. Buck Garden has created a sophisticated way of displaying additional plants in the garden: trough gardening.

Trough gardening was popular in England during the 1920s and ‘30s when gardeners used old watering troughs made from tufa stone as containers for their alpine plants. The troughs were an ideal place to grow a wide selection of plants and were easier to manage then conventional gardens.

What made tufa truly special was its porosity, which allowed great air circulation to the plant’s root system. As the concept took off the availability of natural tufa became scarce and expensive, and gardeners needed to create a replacement.

Eventually the gardeners discovered that a mixture of cement, sand, vermiculite and perlite was a good replica and "HyperTufa" was created. “Hyper” is a prefix meaning excessively or extremely; and tufa stands for the rock it simulates. Put them together and you get extremely rock-like containers.

Tufa is a porous cellular rock formed from calcium carbonate. It is found in limestone country where water has been involved in the wearing and leaching out of the original materials creating a porous, spongy consistency.

In many countries throughout the world this natural stone has been hollowed out and carved for animal watering troughs, decorative stepping stones, antique-looking pots and urns, and planters for favorite alpine plants.

But when metal replaced tufa as the favored material for making troughs and sinks, tufa containers were no longer readily available and gardeners looked for an alternative way to simulate this stone material.

Since tufa was created with limestone deposits and plant matter, the formula of cement, peat moss and sand became a viable alternative. By mixing these inexpensive ingredients gardeners could make a light weight version of stone troughs that could be left outdoors winter after winter without breaking down.

You can find plenty of hypertufa recipes online.

Here are the proportions Buck Garden uses:
1 part Portland cement
1½ parts sifted peat moss
1½ parts perlite

Add water slowly, mixing until the material is the desired consistency. Grab a handful of the mixture and squeeze it; it should hold together and only a few drops of water should emerge. The total amount of water needed will depend on the dryness of the peat moss and the humidity in the air. The mixture shouldn't be runny; too much water and you'll get a weak container.

The container you use as a mold is limited only by your ingenuity. Don’t use wooden or metal molds unless you first line them with plastic, otherwise the mixture will stick to the molds and you will damage the planters when you try to remove them. Most of our hypertufas are made from cardboard, plastic, and styrofoam molds.

After the mix is made, the troughs are molded and then cured. Curing has two stages: an early stage when the planter should not be moved, and a longer drying period following removal of the mold.

The initial curing period takes about 36 hours, while the latter takes about three weeks or more. For the first 36 hours, mist and cover your planter with plastic. The plastic makes it cure more slowly, producing a strong planter. After the initial 36 hours, test the hardness of the mixture with your fingernail. If you can scratch the surface, the mixture is still too soft and should be left for another day or two and then retest. When it requires a screwdriver to scratch the surface, the planter is ready for the second stage of curing.

Remove your new trough from the mold carefully. Gingerly place your object back into the plastic bag and seal tightly. Continue to keep it moist, misting occasionally if needed. Allow it to cure for at least another week, but the longer it can slowly cure in a moist environment, the better. I've seen it written that a one month cure time can result in 25% stronger tufa. Remember: patience is a virtue.

The last step is to leach out the lime contained in the Portland cement. Lime is toxic to most plants and therefore needs to be leached out. We hose down the containers once or twice a day for 5 – 10 days. If you live where it rains a lot, leave the planter out for 1 - 2 months and nature will do the leaching for you.

The hypertufas are then filled with a well-drained gritty soil, and planted. Some of Buck’s hypertufas are home to “sun stroke” loving plants such as achillea and hens and chicks, while dwarf hosta and rhododendron are living a bit on the shady side.

Other favorable plants you will find growing in our homemade hypertufas are: androsace, arabis, armeria, delosperma, dianthus, lewisia, thalictrum, sedum, ferns and miniature conifers. With so many plants to choose from you can design a garden that represents a little slice of a natural ecosystem.

Other materials ideally suitable for landscaping troughs are weathered rocks, pieces of driftwood, moss and slates of stone. These can be quite attractive. Any appropriate top dressing can be used. Certain troughs have chipped bark, or pine needles, while others have gravel and slivers of slate.

Hypertufas are light weight, easy to care for, and can be left outside year round. No matter the size of your garden, or the climate of your region, hypertufas are unique and add beautiful touches to your property. Rock gardening is a major hobby and a source of great pleasure. Visit the Leonard J. Buck Garden and learn more on this rocky subject.

- Tricia Scibilia, interpretive gardener, Leonard J. Buck Garden, Somerset County Park Commission: www.somersetcountyparks.org
**Photos by Tricia Scibilia

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