Potatoes can be a challenge in a small urban space. One of the most popular way to grow potatoes is in a burlap sack, or even by stacking old tires. Now I would NOT use old tires because of the possible asbestos and lead contamination, let alone the rubber itself. I have used burlap sacks, however, in the wet PNW weatehr they will break down leaving you with a bottomless bag by harvest time. Another alternative, which worked well for me, was an old tree planter from a nursery. It was large, light weight, had drainage holes in it, and was free. OK, aside from the purchase of the original tree...but I was REUSEing ;)