This blog is the third of a three-part series.
Building from Blogs
After reading several gardening blogs which enthusiastically endorsed potato towers in spring but never followed up to share how the towers had performed post-harvest time, the staff of Gateway Greening decided to put this technique to the test. Our goal was to see if potato towers are an effective method of vertically growing sweet potatoes as a way to maximize growing space in the home or community garden.
Limited Resources, Limited Testing
Although our staff originally planned to test this method using three towers of various heights and widths, we scaled the experiment back to create just one tower due to soil availability. (At 
the end of the day, expanding school and community gardens comes first. Experiments in the Demonstration Garden come second.)
The potato tower we constructed is close to six feet tall. Built around an irrigation tube (PVC pipe with holes drilled into it) and lined with burlap, Demonstration Garden intern Clara and volunteer Theresa filled the tower with thin, alternating layers of topsoil and compost. Next, small holes were cut into the sides of the tower at regular intervals for sweet potato slips to be tucked in.
Over the course of the summer, volunteers and staff carefully watered the tower by spraying down the burlap sides and also by using a hose to run water through the irrigation tube. Little by little, the slips began to flush out into vines and flourish.
Did it Work?
Although several sweet potatoes were harvested from the tower this fall, Garden Program Manager Dean Gunderson has decided to repeat this experiment again next summer. Technically the experiment was a success – but there was definite room for improvement.
When we constructed our potato towers, we made a fundamental mistake: we planted the tower with sweet potato slips shortly after it was constructed. Throughout the summer the layers of soil and compost settled significantly, damaging the delicate sweet potato slips and their root structures.
As a result, we harvested few sweet potatoes and they seemed to be quite small, as though stunted early on. Our volunteers also observed that all of slips planted in the lower half of the tower died, and suggested that the sheer weight of the soil above prevented the potatoes from establishing below.
Potato Tower Experiment Planning for 2018
In 2018, Demonstration Garden staff and volunteers will be repeating the potato tower experiment with the original (now settled) tower and a second tower that will be shorter in size for comparison. Keep an eye out for photos and updates next spring!
To learn more about experiments that happened in the Demonstration Garden in 2017, please check out our Garden Soxx Experiment and 45 Degree Angle Trellis Experiment blogs.