Sitting on either side of the main entrance to Alderman Hall this summer were two small wooden boxes brimming with salad greens. These little boxes are the current iteration of a project initially developed by Professor Tom Michaels in 2011, and worked on by many undergraduates since then, called hydroponic salad tables. The tables offer a way for people with little to no land to grow their own salad greens.
These tables are small, but pack a big punch. The conventional table is two feet by four feet and holds 24 plants at one time. It might not sound like much, but that adds up to three fresh salads a day for seven weeks. The tables outside of Alderman debuted a new, more compact version called the hydroponic salad bench. It’s approximately 1/3 the size of the table, making it easy to fit in just about any location with sufficient light. The bench still produces enough for one fresh salad a day, which is more than many urban families get.
The key to the success of these little tables is the lack of electricity. They use static hydroponics technology. “It’s like a deep water system,” says Michaels, “but with an air gap between the nutrient solution and the pots so that part of the roots are in the air and absorb oxygen. There’s no need for electrical pumps to power an air bubbler, dribble a nutrient solution, or fill/ drain a tank.” Because of this, the salad tables can be placed anywhere outdoors without having to worry about finding a plugin or tripping over cords.
While the salad tables work great outdoors, Michaels has done some experiments bringing them inside as well. Unfortunately, indoor natural light isn’t quite enough for the salad tables, even with a south-facing window. However, getting a good grow light system set up over a salad table has been shown to yield nearly as many fresh greens as planting outdoors.
The tables are easy to set up, and $60 can purchase enough building supplies, nutrients, and seeds to last several years. Interested in creating your own salad table? Read more of the research behind them and download construction plans at z.umn.edu/hydroponicsaladtables.