Oca (Oxalis tuberosa)
We have been growing oca tubers for many years, having been given a handful of seed, a bit like Jack and the beanstalk over 10 years ago!
What are ocas?
Ocas are a tuber root crop from the Andes where they are a staple food, second only to potatoes. They are grown commercially in New Zealand where they are known as Yam. Ocas belong to the wood sorrel family.
Why grow ocas?
They are very easy to grow, give good yields, and are delicious to eat.
The folliage makes a nice decorative border which is a great weed suppressor, with lots of small yellow flowers in late summer and early autumn.
They are still relatively unknown in Europe and are not grown commercially outside their native Andes except in New Zealand.
They store very well throughout the winter. Tubers left on a shelf in a shed were still perfectly edible in April, and grew when planted.
They are disease free, and you can save your own tuber seeds from year to year.
How to grow ocas?
Ocas are very easy to grow. They don’t suffer from blight and are very disease and pest resistant, though in wet years, slugs do seem to like them. The only thing required to grow oca is patience: they need a long growing season as the tubers don’t start forming before the autumn equinox. For this reason, they may not be suitable in areas where there is danger of an early frost, as this will kill them before the tubers have properly developed.
Ocas are basically grown like potatoes, although they are more shade tolerant, and in fact, will do better in partial shade. Plant them out after the last frost, at 30 – 40 cm spacing and at a depth of 5cm, and wait. After a few weeks, small stalks with clover like leaves will appear. They may appear quite weak and fragile at this stage, and it is important to keep them free of weeds. After about two months, earth up the stalks or mulch (this is optional, but recommended as it increases yields). You can pluck a few leaves throughout the summer to add to your green salads. That’s all there is to do until the first frost kills the plants in November or December. Wait for about a week after the plants have died back, then dig the tubers up. They are grow very close to the surface unlike potatoes. If you don’t have early frost, leave them in the ground till early December for the biggest yield.
How do I get started growing ocas?
You will need to get tuber seeds.
In the winter, we usually have tuber seeds of plants naturalised to Ireland and are happy to post some to you if you are in Ireland, the UK or anywhere in the EU.
It’s now to late for the 2014 harvest, and you will have to wait until the 2015 harvest is in, probably in December.
We mostly harvest a red variety which we have been growing successfully for the past 8 years, and which has shown good disease and slug resistance and gives good yields. We usually have also have a small amount of an orange and a white variety.
Ocas are very versatile vegetables. They have a slightly tangy taste and a delicious crunchy texture when raw. It is a good idea to leave them in the sun for a few days once dug, as this sweetens the flavour. The texture gets more floury, and the flavour sweeter, once they are cooked.
They can be used raw in salads, stir fried, cooked in curries, stews or soups, steamed (and served with butter or honey) or brushed up with olive oil and roasted (the best way in our opinion). Oca cooks more quickly than potatoes or even sweet potatoes, so check early on if they are done.
There’s no need to peel them, just wash them (which is easy thanks to their slightly waxy skins).
The leaves can also be eaten and make an interesting addition to a green salad (although you shouldn’t eat too much of them as they contain oxalic acid).