above ground potatoes?

[svalli]

I have some "feral" potatoes growing in the garden in area were I did not plant anything this year and was growing potatoes year ago. Today I noticed a wilting potato branch sticking out from the garden fence and some purple berries on it. I picked up the branch to take a closer look and those are not berries, they are like small tubers with leaves growing from them. There are some still green potato plants on the other side of the fence, but none of them have these small tubers on branches. Has anyone seen this before? I wonder if these tubers would root, if I planted them. Too bad it is getting cold soon so, I can not experiment with them.