oca (oxalis tuberosa) yet? It’s one of our current favourite root vegies and is commonly known as New Zealand (NZ) yam, however it’s real origins stem back to the Southern Andes. NZ seems to have a thing for adopting foods and calling them their own, think kiwi fruit which actually comes form China where it’s called the Chinese gooseberry. And just for the record feijoas, which NZ folk grow with great vengeance are actually from South America. To be fair oca was introduced to NZ way back in 1860‘ish, so it’s been around for a while on this side of the world.
As you can see above – there are quite a few varieties, some common and some you’ll probably never see in real life.
How to grow themGenerally you plant oca in Spring in cool climates, however we didn’t get ours in until mid Summer and they still worked just fine. Similar to potatoes you pop oca tubers in the ground and wait for them to stick their heads up. You can gradually mound earth around the plant (again, like potatoes) to increase the size of the tubers, or you can just let it grow and still achieve a good harvest. Interestingly, tuber development is light-dependant. When daylight hours drop (in Winter), the tuber formation begins. We actually checked on our oca crop in late Autumn and there was nothing going on under the soil – lots of leaf, but not one little tuber was spotted. However around two months later they’ve magically appeared – it’s so crowded under each plant with stacks of tubers, it’s a pretty impressive little plant.
How do you know when to harvest?Like potatoes, when the leaves start to die back it means the tubers are reading to be harvested. It’s good to know that oca is more perishable than potatoes, but if properly handled can be stored at room temperature for some months.
Oca crop dieing back meaning the tubers are ready to be harvested.Remember to store the biggest, fattest, healthiest tubers for propagation for next season. You can do this in a bucket of dry sand or sawdust or in a cool dark and dry place. We store ours in a couple of places, sure most go into one of our cool dark cupboards, but we also have a big bowl of them on our kitchen bench. Mainly so we can access theme quickly for easy eating – we find that doing this for a short period doesn’t affect them at all, i,e, they can handle of bit of sunlight… Which potatoes can’t.