This "sweet potato" was a crop found by the Destiny expedition on a Jungle planet in an unnamed galaxy and was named by MSgt. Ronald Greer based on its appearance. In actuality, the plant has a very unpleasant taste, but is edible.
Greer was first to taste this plant and tricked several fellow crew members into believing it was tasty. Airman Darren Becker has prepared it in many of the ways an Earth potato is prepared, including mashed. While working on the Destiny interface chair, Jeremy Franklin asked Eli Wallace to get some of this mashed "sweet potato" from the Mess Hall, affording him enough time alone to sit in it. (SGU: "Justice")
Dr. Adam Brody also extracted some purple dye from these to use in a practical joke on Sgt. Hunter Riley, unfortunately Riley heard about the prank and had a pre-recorded Kino video play while Brody and Eli Wallace watched. When Brody went to investigate he ended up covered in the dye. (Kino: "Wait For It")