Oca, or New Zealand yams, are a small, brightly coloured tuber from the Andes in South America. Their taste is similar to the potato, but with some tartness. I think they are very pretty!
I planted a couple oca in an up-cycled recycling bin two Summers ago. When I harvested them, I left the smallest tubers in and pretty much left them alone after that. Here it is the fruits of their second season, and while the harvest is small, it took hardly any effort to grow. I once again left the smallest ones in the ground.
The oca has not got any known pests in New Zealand and needs little care except some soil amendments. However, they have a long growing season, starting growth in Spring and ready to harvest in Winter in my region. You can harvest sooner, but I have heard they need the cold or they will not be as sweet.