All hail this humble container. With a tray for soil up here and a reservoir for water down there, a "self-watering" container can be made to produce a sizable crop of vegetables, fruit or flowers — without a spacious garden site. Any concrete pad, balcony, rooftop or classroom will do.
"If you have the luxury of gardening in the ground in a small plot, that's fine," said Greg Stack, an extension educator with the University of Illinois, who teaches horticulture in the Chicago area.
"But many of the people I work with are doing container gardening on patios and porches. While they won't grow tons of produce, their containers will fill most of their family's needs during the season."
You can fashion your own self-watering container from sturdy discards, or buy one ready-made. All operate basically the same way, with water reservoirs on the bottom that are filled via pipes or openings at the top or side. Another tray fits over the reservoir, supporting the soil and the plants. Water wicks upward to the plant roots where and when it's most needed.
Some containers come with plastic sheets stretched over the top to reduce evaporation loss. The containers "are great options for people no matter where they live or what conditions they have, as long as they can find some sun," said Frank DiPaolo, general manager of EarthBox, a line of self-watering containers.
Standard commercial containers run 30 inches long, 12 inches wide and 12 inches deep. They weigh about 70 pounds when filled with soil and water, DiPaolo said.
"We make ours so they can put casters on them and wheel them around," he said.
The EarthBox line was developed in the mid-1990s when a commercial tomato farmer wanted a more efficient way to grow produce than was being done on a factory farm.
"We went looking for a better method of controlling the environment," DiPaolo said. "By using a box, we're able to control the amount of water and food needed to feed the plant. Whatever we put in the box stays in the box or is used up by the plant.
"We need only about 20 to 25 percent of the water that farmers use in the field and about half the fertilizer."
Many of these containers need water refills only about once a week if the plants are young. The frequency of watering depends on whether the containers are sitting in full sun or partial shade, and on peak daytime temperatures and plant size.
"As plants ripen, I recommend watering once a day when it's hot," DiPaolo said. "The EarthBox holds just under 3 gallons of water. Two full-size tomato plants can drink that down in a day."