All about Oca

Many years ago a friend of mine asked me to taste a small bulbous root he had just dug out of his garden.  To my surprise the raw tuber tasted rather like a crunchy juicy carrot/apple.

He gave me some to plant in my garden, and for the next few years I happily used the small tubers sliced raw in salads and cooked in mixtures with carrots and other vegetables.  My friend called them 'yams'.  This is what they looked like:

That was a long time ago.  I moved house a number of times, forgot to dig out my 'yams' and take them with me, so I had not grown them for many years when last year I saw a little bag with six of them for sale at a local market.

I was surprised when I looked up 'yam' on the internet and found an entirely different much bigger tuber, not at all the ones I had.  I concluded that my friend's name for them was wrong.

I now know that their real name is 'Oca' and that they originate from the Andean highlands in South America.  South American Indians began to grow Oca crops a very long time ago.  Andean farmers now cultivate numerous varieties of Oca.  Ocas were first grown in the West in 1829 in England. Ocas have been grown in New Zealand since 1860. New Zealanders call them 'yams' (not the first time New Zealanders rename a species).

The Latin name for Oca is Oxalis Tuberosa, and, yes, the foliage (see below) is clearly that of Oxalis, but fear not, this is not an invasive variety that you can't get rid of.  

I planted my Oca tubers at the end of September last year.  At the end of February the foliage of each plant was around 30 centimetres high and covered a circle of soil around half a metre in diameter.  I thought 'rather than digging up an enormous crop at the end of the season, let's dig up some now and begin to use them in salads'.  That was the wrong idea.

When I dug out the first plant I found to my amazement that all this prosperous looking foliage came out of the tuber I had planted half a year earlier, with no additional new tubers formed at all.  Disappointed I decided to leave the other plants in the ground.

At the end of June time was up for these non-performers. I parted the extensive foliage and found:    

Woow!  A rich crop of new tubers had formed at soil level and slightly below soil level.

When I researched Oca a bit further I found out that Oca performs well in temperate conditions.  It will not grow well in the tropics.   Plant Oca in Spring around 5 centimetres below the surface.  It likes nice friable slightly sandy soil, but tolerates poor soils and cool conditions because of where it comes from. In years when I did not water them well, they did not produce much, so adequate watering is required!

Oca will die back in Winter if there is frost and re-emerge in Spring. All this makes sense if you realise where it originates from: the Andean highlands.  Cultivation is very similar to potatoes, including hilling.  Like potatoes Oca tubers are ready to be harvested when the foliage starts to wilt.  After harvesting Andean farmers leave tubers in the sun for a few days to sweeten them.  I guess my Ocas where sweetish without this treatment because they were mostly at ground level and had never been hilled.

Ocas do not taste like potatoes.  Don't peel them, just give them a good brush.  The uncooked juicy crunchy slightly sweet flesh is great in salads.  They are also nice steamed (just for 5 minutes) or in stir-fries.  Oca is a valuable source of potassium, vitamin C and iron.  In South America the raw fruit is sometimes pickled with vinegar.

This season I planted 10 Ocas in a small area 70 centimetres x 70 centimetres. I planted them late - mid January. In mid June I harvested 2/3 of a bucket!

 Try Oca!