New Zealanders once again (as with kiwi fruit) try to rename a plant from another part of the world as if it was theirs. It actually comes from Bolivia/Peru area.

I have normally found oca (no need to write it in caps) to have a texture like salad potatoes, but no doubt there are hundreds of varieties. I've eaten them in Bolivia (roasted), and found them occasionally in Waitrose (imported from, er, New Zealand). They are useful in the Andes because they can be grown at a higher altitude than potatoes. I saw them being cultivated on steep hillsides above 4200m (14,000 ft). A lot of plants like this don't grow so well in the long daylengths of higher latitude summers, which may be why they do their main tuber formation in the autumn here.