Plant of the Week: Trough Gardening
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Plant of the Week
I have a passion for plants. They need not be large and showy to attract my attention; just different and interesting works just fine.
Growing an assortment of plants in a garden presents some challenges, especially when the plants in question require special conditions or are especially small. As a remedy to these problems, I have employed the use of garden troughs.
Trough gardening is a form of rock gardening that originally developed in 19th century England during the heyday of the Industrial Revolution.
As a middle class developed during the Victorian age, a new social phenomenon emerged - the vacation. One of the great vacation trips of the era was to visit the mountains of Europe during the summer, when all of the wee alpine plants were in bloom. Seeing all of these small gems in their full glory spurred the rock garden movement, as travelers dug plants and took them back home.
Success must have been spotty at best, but gardeners are an inventive lot. They found that growing the plants in hand-hewn cattle watering troughs was an ideal solution for finicky plants that required especially sharp drainage and specific soil conditions.
These hand hewn watering troughs were usually made from tufa - a natural limestone formation that occurs when mineral saturated water comes in contact with sunlight and air. At the mouth of springs, moss and algae grow in the water and form a concretion of limestone with lots of open pore space, making a kind of rocky Styrofoam. As a stone, tufa is lightweight and easily worked, yet still strong.
Many of the troughs I use are hyper-tufa troughs made from combining Portland cement, peat moss and perlite. These can be formed in about any size and shape and make ideal all-weather containers. Most of mine are about 18 inches long, 12 inches wide and 6 inches deep and - if you have a good imagination - look more like a limestone rock than a piece of concrete. But I don’t limit myself to these. I also have various size porcelain washtubs, the aluminum base to my old barbeque grill and even large clay pots. And, thanks to a find at the local farmer’s co-op, I now have a real concrete cattle-watering trough about the size of your average coffin.
I have tried various potting soil blends in these containers and have found that a good high quality artificial potting soil used by greenhouse growers is a good place to start. Because these artificial soils are half organic matter - either composted pine bark or peat moss - they tend to shrink as the medium ages. This shrinkage in volume decreases soil drainage, a critical factor for plants grown in troughs. I usually add about 15 percent by volume coarse sand and 10 percent medium size granite chips (also available from the co-op as a digestive aid for chickens) to counteract the soil shrinkage.
For most plants I don’t worry too much about the soil pH, keeping it in the 6.0 to 6.5 range that is agreeable to the vast majority of plants. But with trough gardening, it is easy to create some troughs with alkaline pH conditions or very acidic soils for plants prefer those conditions.
Deciding on what to grow in these containers is the most fun. Troughs provide an ideal location for small or non-vigorous plants that would easily get lost or be overpowered by more aggressive neighbors. I crowd lots of these small plants together in the same container and, as usually happens, prune the more vigorous plants back as needed to assure room for the less vigorous species. Typically, I will have six to eight different species growing in one square foot of surface area. In the larger containers, I also like to underplant with bulbs of species tulips, crocus, alliums or other minor bulbs.
One of my oldest troughs - now about 10 years old and hardly touched during that period - is an old washbasin containing an assortment of hens-and-chicks. I have trouble keeping these plants alive when planted in the ground. But the extra drainage provided by the container has been the ideal solution.
Another favorite trough I call "plants from the 80," a collection of little plants I’ve collected from the 80-acre farm where I grew up. My large concrete trough is home to many of the penstemons from the Rocky Mountains, which haven’t persisted well when planted in the soil but are doing fine in the trough.
Maintenance is easy. Most of these trough plants are not heavy feeders, so I only fertilize lightly once a year in the spring before growth starts. I use either a slow-release pelleted fertilizer or compost from my oak leaves, to which I have added a bit of slow-release fertilizer. My troughs are mostly watered by my irrigation system, which I run once a week. Because most of these plants are small-leaved and adapted to dry and rocky conditions, they simply do not need as much water as the leafy plants usually seen in patio container plantings.
Reworking the troughs need not be frequent. I usually remove, replant and spruce up troughs on an ongoing basis, as I have to find a home for new plants. If a trough is happy and successful, reworking will not be needed more than once every five or so years.
Another advantage to trough gardening is that it gives me a place to display the rocks I drag home whenever I make a road trip to some new area. These rocks, usually about the size of my fist, are always interesting but too small for any practical purpose. But, when added to a trough garden, they add interest to the plants and transport you back to the place where the specimen was collected.
By: Gerald Klingaman, retired
Retired Extension Horticulturist - Ornamentals
Extension News - March 18, 2011
The University of Arkansas Division of Agriculture does not maintain lists of retail outlets where these plants can be purchased. Please check your local nursery or other retail outlets to ask about the availability of these plants for your growing area.