Here is a photo of some oca growing in 8" pots.
another shot showing developing tubers.
I was able to get 39 marble to golfball sized tubers from a plant of this size indoors under lights. I believe a person just about anywhere could grow oca useing this method. The key being not interrupting the "dark cycle" (must be at least 12 hours continuous darkness for tuberization) during tuberization.