Oca is one in the great list of Andean tubers, and you can read all about it here (it's William Woys Weaver! You know you want to). I ordered some tubers this spring, got them when it was too cold to plant them outside, forgot about them until well after the summer-vacation-that-happened-right-after-a-frost, and finally planted them (well-sprouted) in a planter. Where they are doing fine:
As you can see, they are an oxalis, related to common wood sorrel and also that gorgeous redwood sorrel we became acquainted with in California (and I nibbled on, mostly to show off).
Anyway, they are daylength-sensitive, and don't start forming their tubers until probably late October-early November (I checked today, and nope, no tubers), so this is going to be interesting. I guess I will cover the planter with some plastic braced up on... something, and hope I can keep them from getting frost-bitten until it's time for harvest.
I was thinking of taking the planter along to the Harvest Festival this weekend, but I don't think I want to explain all of that to anyone who asks. So maybe next year, if I manage to grow them out successfully this year. I'll keep you posted.