Crap Crops of the Incas: My on-off-on affair with high altitude Andean root crops 1) Oca

Some people remember where they were when Kennedy was shot, when Lady Di and Prince Charles got married, or when Nelson Mandela was released. More vivid in my mind is the day I first held an oca tuber in my hand. It was an object of startling beauty - a bright red blob of sealing wax with embryonic buds pushing out from its furrowed brow. I don't remember the date exactly - early in 1987 or 88 seems likely.

I knew of the plant of course. I had a well-thumbed copy of the Oxford Book of Food Plants, which contained an illustration of oca (Oxalis tuberosa) along with concisely informative text. The clover-like leaves and ivory coloured tubers certainly looked interesting. So I was delighted when the HDRA members' experiments for that year included an oca trial. Like a First World War volunteer, I signed on the dotted line and awaited my fate. Opening the package and placing the tubers in my hand engendered in me a strange sense of excitement, a connection with the past and the distant Andes, certainly, but something else: the intoxication of possibility. Might it be possible to create mixed or intercropped oca/potato crops as has been done since time immemorial in the Andes? Might this novelty crop actually become incorporated into the mainstream as had started to happen in New Zealand a few decades earlier?

So anyway, in terms of its visual appeal, this oca exceeded my expectations. It was certainly a brighter shade than pale, a bobby dazzler, a stunner. I was in love. Truly. Madly. Stupidly.

The tubers were meticulously tended in pots and then planted out after the last frosts. The resultant plants grew well in our garden, producing masses of lush trifoliate foliage and a scattering of eggy yellow flowers that looked a bit like brassier versions of the native wood sorrel that grew nearby and is in the same genus.

As we all know, love is a kind of madness which leaves the victim deafened and blinded to reality. The painful shortcomings of my new love were ignored even when the frosts came and we lifted the crop. "But the tubers are beautiful", I told myself and anyone else who hung around long enough to listen as I cradled the equivalent of a mouse's breakfast in a vastly optimistic basket. Oca was simply all mouth and trousers.

Eventually things cooled off between us. I came to see, finally, that oca was another one of those faithless crops which, although quite well adapted to our moderate summer temperatures, just refused to tuberise until around the autumn equinox. Cue the first hard frosts and another season of empty, unfulfilled promises.

Besides, by this time Lost Crops of The Incas had been released. An eminently readable guide to the incredible treasure trove of Andean crop plants, this provided me with many more plants to pursue, possess and cultivate. I remember reading the majority of it at one sitting, from bedtime until breakfast, so fascinating did I find it. If oca was a busted flush, there was always maca, ulluco, ahipa, achira, arracacha, mashua, yacon or mauka - an astonishing array of subterranean homesick crops to try out in the soil of dear old Blighty.

Oca, unlike her erstwhile bedfellow the potato, has pretty much languished outside south America, apart from New Zealand where autumnal frosts come late enough for decent tubers to form. Yet the first potatoes to arrive from south America were similarly temperamental, low yielding, day-length sensitive prima donnas. By a process of selection, the original andigena potatoes were converted into day-neutral spuds - sow some seeds, keep the highest yielding varieties, allow them to cross pollinate and keep selecting. In a hundred years or two you've got yourself some decent varieties.

Hold on. Not even Coenzyme Q10 and goji berries are going to keep me around that long. Besides, who's ever seen their oca plants produce seeds? Flowers maybe, but no seed pods. No seed pods, no shuffling of the genetic playing cards and no chance of any random mutations popping up that might reset the alarm clock. Things seem to be looking up, however........

Despite oca's manifest limitations, we have undergone a rapprochement and I have been growing it steadily for more than a decade, picking up different varieties as and when they
become available. By 2007 I had maybe half a dozen varieties collected from fellow enthusiasts. A number of these flowered at the same time. Pursuing the wholly unscientific method of poking the flower of one variety into another, I managed to get some seed pods to form. This was a surprise. Ben Gabel of The Real Seed Catalogue who offers several oca varieties also managed to get some pods to develop on his plants. Unfortunately I was away while most of the pods on my plants were ripening. I did manage to collect some seeds when I got back, however. Ben was also successful.

It turns out that oca is tristylous, that is there are three different flower types which vary in the height of the stigma, the female bit, relative to the position of the stamens (the male bits). Something similar occurs in primroses, where two types occur: pin eye (stigma sticks out above stamens) and thrum eye (stigma below stamens). It's a mechanism designed to ensure cross pollination and prevent inbreeding.

But what if all your varieties of oca have the same type of flower? No seeds are produced. Somehow or other, the combination of compatible varieties and favourable weather in 2007 led to the formation of seeds for what may have been the first time in Britain.

Both Ben and an intrepid plant collector and grower from Belgium, Frank Van Keirsbilck managed to get a few of the seeds to germinate. By autumn 2008 there were two new varieties of oca in existence, Ben's one and Frank's one; the latter has decided to call his one "Pink Dragon", in deference to its conception in Wales and the colour of its tubers. OK, Barack Obama's inauguration is undoubtedly an epochal moment. But don't forget 2008, Year of the Potato and the advent of the first European ocas. Andean crop anoraks make a note in your diaries!

T.S. Eliot claimed that "April is the cruellest month". Early December's not much better. In a moment of grey-day induced ennui, I suddenly remembered those oca seeds, stashed away in a Petri dish, forgotten and possibly dead. I felt an overwhelming desire to plant them or be rid of them. I had read a paper which described sterilising oca seeds in 10% bleach and soaking them in KNO3 overnight to improve germination, so that's what I did.

To my surprise, some of them actually germinated. Here's what they look like now:

Among this mongrel brood there are definite differences in leaf and stem colour, probably reflecting different anthocyanin levels. Some are certainly more vigorous than others. As the plants develop, I will post additional mugshots.

What we need to do now is find out how to get the plants to flower consistently, identify which plants have which flower types and cross pollinate like mad to get as many seeds as possible. That will give us the best chance of developing day-neutral varieties. We're also hoping to obtain some more varieties. It's a numbers game when all is said and done.


Anonymous said…
Hi Owen,
the small seedling looks very good, I took a picture of my seedling, but unfortunately it disappeared. I did note however that there was only one 'true 'leaf for a long time, and the stem of the leaf was a bit longer and thinner. But maybe you have some that look like this as well. If you plan to grow it until autumn, which I suspect you'll do, it will have a long growing season, I did get a quite big harvest from my seedling, 16 tubers, and three cuttings that produced one tuber each, makes 19 tubers,not bad for a tiny seedling sown on February , 20. And, obviously the seeds stay viable for over a year, good to know!
Keep up the good work,
Anonymous said…
Sounds exciting
Catofstripes said…
I've had a couple of varieties of Oca (origin New Zealand via Waitrose) for several years but they've never flowered. I was really surprised when the white form from Realseeds made oodles of flowers this year, I just wasn't expecting it.
Rhizowen said…
Hi Catofstripes

Some years some oca varities flower in midsummer, well before the autumn equinox. I don't know why, neither does anybody else I've asked. The white variety seems to be one of the most profuse in terms of flower production. The orange variety that Real Seeds sell is also a reliable flowerer in my experience.

Well done for spotting ocas for sale in Waitrose. Are they orange a la Real seeds, one perhaps with noticeably darker eyes, or are they different, perhaps even purplish? I've never seen it in our local Waitrose......
Catofstripes said…
You can see examples here

I would describe the colours as a shocking pink and a crimson but it's a very subjective thing. The foliage is very slightly hairy, the white sort's leaves seem waxy in comparison.
Anonymous said…

I plan to try some Oca crosses myself this season. I have a least 3 varieties so will hopefully get some seed set. I would love to see some day length neutral varieties become available. Oca is such a trouble free crop in every other respect it's a shame that its productivity is hindered by day length.

I'll follow the progress of your seedlings with great interest.

All the best.