Make a hypertufa container that's perfect for rock gardening, alpine plants, or a birdbath.
Form weathered-looking stone containers from hypertufa, a blend of cement, peat moss, and sand. It's easy, fun, and satisfying. Hypertufa containers -- or troughs -- make natural additions to the garden as well as handsome homes for alpine plants on a patio, deck, or balcony. Next thing you know, you'll be making them for all your friends and family.
June Skidmore of Mercer Island, Washington, creates and sells hypertufa troughs. As a gardener fond of alpine plants, June perpetuates the concept of trough gardening made popular in 1930s England. She explains how old stone troughs, once used to water farm horses, were turned into lovely container gardens, which were especially appropriate for small plants that might otherwise "get lost" in the garden. Other containers were made from shallow old stone sinks -- taken outdoors from the cottage and planted.
Although various methods exist for making hypertufa, June shares this technique, which she has found to work well and weather the seasons.
Choose a mold of a desired size and shape: square, rectangular, round, or oval. We used an 11 x 13 x 14-1/2-inch plastic dishpan -- the finished trough slides out easily, and the mold is reusable. We also used a foam box liner (rescued from the trash; 9 x 15 x 5 inches) to make a cold-hardy container. In this case, the mold remains part of the trough; the foam insulates the hypertufa and helps plants survive cold winters. If you choose a metal or wood mold, line it with a sheet of plastic or a garbage bag before shaping the hypertufa in it.
Start with a small container; progress to larger ones when you feel more comfortable with the process. If you prefer to make a birdbath, use a garbage can lid for a mold.
Work on the floor of a well-ventilated area where it's OK to make a mess, such as the garage or basement. Spread out a tarp or large sheet of plastic to make a washable work surface; clean up with a hose.
Troughmaker June Skidmore recommends "aging" hypertufa (encouraging moss growth) by painting the outside of the trough with yogurt. Keep the trough moist and shaded until moss develops.
1. Wearing rubber gloves and a face mask to protect yourself from caustic portland cement, premix dry hypertufa ingredients in a 5-gallon bucket. Use a plastic milk jug (cut into a measuring scoop) or coffee can to measure ingredients 2 gallons at a time. Thoroughly mix 1 part portland cement, 1 part sand, and 2 parts peat moss. Scoop out premix as needed for each project; store the remainder in the covered 5-gallon bucket.
2. Transfer 2 gallons of premix to a plastic dishpan or similar reusable container, and make a well in the center of the mix. Slowly add water, blending it with premix until mixture holds together but isn't sloppy (the consistency of thick mud). If the mixture is crumbly, add water; if sloppy, add dry hypertufa mix. Blend more dry mix if needed; once it's wet, it must be used.
3. If using a reusable mold, firmly press mixture into bottom of mold to form a 2-inch-thick base. Stand one or two dowels (depending on the size of trough) in bottom of container to create drainage holes. If you're using a foam ice chest or box liner, see the option below.
4. Continue pressing hypertufa mixture up sides of mold until trough is completely shaped (1-1/2 to 2 inches thick). Smooth and shape top edge using a trowel; mist with water to smooth.
5. Decorate the edge of your trough, if desired, with small shells or stones while the hypertufa is moist. Set the trough on a large sheet of plastic (or a garbage bag), wrap it up, and set it aside to dry for a day or two. The plastic allows the cement to cure properly and the trough to dry without cracking. Then unwrap the trough and remove the reusable mold. Remove dowels from drainage holes.
6. Scrape and score outside of trough with a wire brush to roughen it and make it look more like stone. Round off top edges and corners, if desired. Allow trough to continue drying and curing for at least 3 weeks outdoors in the elements. Finished hypertufa pieces are heavy as stone but not as heavy as concrete.
Option: If working with a foam mold, press hypertufa on the outside of the mold first. Work up to the top edge, then allow trough to dry by wrapping in plastic and curing for two days at room temperature. After the outside of the trough has dried, unwrap it. Press hypertufa along top edge of trough and 1-2 inches down inside the mold. Smooth and shape top edge; decorate, if desired, as described in Step 5. Re-cover with plastic and allow to cure. Finish as in Step 6.
Before adding plants, neutralize the portland cement by rinsing the finished trough with 1/2 cup white vinegar in 1/2 gallon water. Allow container to dry.
Place a piece of wire mesh over drain holes to allow water to drain without losing soil and to prevent slugs from creeping into the trough.
Make a planting mix that holds moisture and drains well by combining equal parts humus, peat or leaf compost, and sand.
Plant the trough with an array of sun-loving alpines or slow-growing plants that have similar needs and are adapted to your climate. Cover the soil with 1/4 inch of pea gravel to help hold in moisture and give the garden a finished look.
Set the trough on top of a concrete block, bricks, or hypertufa blocks in a protected place where it receives morning or late-day sun. Water the trough garden regularly (every other day in hot weather) throughout the growing season. Do not allow the garden to dry out. Water it with diluted fertilizer once a month. Over time, troughs develop mossy, weathered-looking character.
Select from a huge array of compact, low-growing, and dwarf plants including varieties of: Alyssum, Armeria, Campanula, Dianthus, Gentian, mosses, Primula, Saxifraga, Sedum, Silene, thyme, Viola.