Oca (Oxalis tuberosa)
Other than the potato, oca is probably the most well-known of the Andean root and tuber crops in the northern hemisphere. Oca is also known as New Zealand Yam, although it is native to the Andes, not New Zealand. It is still an uncommon crop, but is growing in popularity. Oca is prepared much like potatoes and can be readily substituted into most recipes that call for root vegetables. Cooked, it is slightly softer than potato, usually with a more acidic flavor. It is commonly likened to potatoes with sour cream already added, although flavors range from strongly sour to mild and squash-like. It can also be eaten raw and is crisp and something like a less sweet apple this way.
Like potatoes, oca is normally grown from tubers, which is how varieties are maintained. Oca can also be grown from seed, which are primarily used by breeders to produce new varieties. If you are in doubt about whether to buy tubers or seeds, you probably want tubers.