At University of Toronto Mississauga, a plastic tower sprouts produce including curly starbor kale, buttercrunch and collard greens.Rising almost six feet off the ground and illuminated by high output fluorescent bulbs, the indoor farm wall grows plants hydroponically – with nutrient solution, instead of soil. The water nourishes the roots, collects in a gutter and then recirculates back to a nutrient tank that feeds back into the hydroponic system.