SUSTAINABILITY
ANNE MARIE VAN NEST
Wicking Beds: Bottom-Up Sustainability
An ancient technology practiced by the Aztecs 2,000 years ago, wicking beds are gaining popularity for their sustainable use in gardening and urban farming. Basically, they use the design principles of selfwatering containers on a larger scale to garden sustainably outdoors. They are self-contained, raised beds that use capillary action to draw water from reservoirs beneath through a wick to the plant roots. This eliminates water wasted on off-target irrigation and reduces maintenance because the water reservoir can sustain plants for days or weeks at a time. The beds can be automated by adding a water-level sensor to refill the reservoir.
“ Wicking beds are gaining popularity in Australia for growing high-value annual vegetables for kitchen gardens,” says Angelo Eliades, a passionate forest gardening advocate with Deep Green Permaculture, in Melbourne, Australia( Australia is the world’ s driest continent).“ Typically only the most expensive veggies would be grown in a wicking bed, as the cost-per-square meter of gardening space is very high. This is a factor that restricts their widespread use. The capability of self-watering over an extended period is a blessing for school produce gardens, where the gardens are often unattended over the holiday periods, especially during the peak of summer.”
LESS WATER USED
John Ditchburn, a lifelong vegetable grower with Urban Food Garden in Ballarat, Australia, notes that wicking beds use 40 to 50 percent less water than conventional garden beds.“ Wicking beds are usually made with timber sides and a pond liner at the bottom to act as a water reservoir, but they can also be made out of plastic tubs or any other container that holds water and does not corrode when in contact with soil,” he says.
Wicking bed cross-section design shows the components of the system.
Since wicking beds are raised, they’ ll warm up quicker in the spring than in-ground plantings, says Rob Avis of Verge Permaculture, Calgary, Alberta, Canada. On the flip side, that means they’ ll freeze sooner in the fall and are more vulnerable to winter freezing and thawing. To offset this, he recommends attaching cold frames to the wicking beds, or covering them with insulating fabric for added protection.
Avis cautions that there is a physical limit to the distance that water will travel upward.“ When designing your wicking bed, it’ s important to keep the depth of the media-filled water reservoir at or below 12 inches( 30 cm) as the capillary action struggles to lift the water higher than that. The soil layer should measure 12-13 inches( 30-32 cm).”
BENEFITS PAY OFF IN LONG TERM
According to Ditchburn, the cost of building a wicking bed can be three to four times that of building a conventional raised bed of the same size. Eliades says,“ Building a wicking bed is a costly exercise, if done properly. There is a lot of embedded energy in the materials used, namely the pond liner, which also happens to be one of the most expensive components, and also one of the most critical ones. All materials have a finite life, so using a pond liner with a longer warranty will ensure that the wicking bed will have a long service life that will return the cost of the materials and offset the energy used to manufacture all the construction materials.”
If you’ re relatively handy, wicking beds can be a do-it-yourself project.“ The skill level required
ILLUSTRATION COURTESY JOHN DITCHBURN
18