Tuesday, 17 May 2011

Oxalis Corymbosa — a Second Look

Regular readers may remember back in July last year I noticed (and tasted) the root of this weed, the Lilac Oxalis, and was impressed enough to consider growing it in more favoured conditions to see if the root would increase to a more useful size.
But planning is not the same as doing, and it never got done.

Recently however I noticed a huge specimen of the same plant growing in a pot. The pot was one of many containing a motley collection of sick-looking house plants, on the window ledge of the company I work for. The oxalis had obviously moved in, and made a take-over of the pot having smothered the less vigorous original occupant.
I could have asked permission from the Keeper of the Plants, but she was deeply engrossed in some spreadsheet. No point in disturbing her for such a trifling matter, so into my courier bag with the pot. This plant was swiftly liberated, destined for important food-crop research duties.
At home, washing off the compost, I was slightly disappointed to see not one large edible tap root, but many small ones; what appeared to be a huge plant was in fact a colony of individuals, each with several edible roots of average length 30mm.
It seems that good growing conditions simply increase corm formation, and subsequent natural vegetative propagation, without the individual roots increasing in size. In fact the resulting congestion is probably detrimental to root size.
Rubbing off the corms as they occur to keep the plant 'solo' might result in a larger root, but that's never going to be practical on any scale.
So it looks like repeatedly collecting and growing out seed while selecting for root size is the only way forward.

Vigorous, easy to propagate, shade tolerant, disease free, and tasty. Only the size is wrong.

For now, I've repotted some to increase my experience with the plant.
The others? Mmm, they do taste good!

Update, 4th August: a shot of the plant in flower...


  1. Is there any chance to cross Oxalis tuberosa with other Oxalis species ? Especially to get rid of that annoying day-length issue. I found a very interesting paper about the supposed origins of domestication of Oca : http://wisc.academia.edu/EveEmshwiller/Papers/116970/Origins_of_domestication_and_polyploidy_in_oca_Oxalis_tuberosa_Oxalidaceae_3_AFLP_data_of_oca_and_four_wild_tuber-bearing_taxa
    I think they must be closely related enough to be able to cross them.
    If you're a bit dreamy, you could imagine that Oxalis chicligastensis, which appears to be the most southern on the map, wouldn't be day-length sensitive, just as Solanum tuberosum subsp. tuberosum which has been crossed to day-length sensitive Solanum tuberosum subsp. andigenum to make the potato varieties we know today ( sorry, the caption is in French ) : http://upload.wikimedia.org/wikipedia/commons/0/0c/Solanum_tuberosum_distibution.svg
    Never stop dreaming ;-)

  2. Hi Julien. That's an interesting article, thanks for the link. Crossing with wild oxalis relatives could throw up some wild variations, but I'll be trying to get oca to cross with itself first. That seems hard enough!

  3. I actually pulled up what I believe to be Oxalis latifolia, growing in containers. A good portion of the translucent tubers were bigger then Oca.

    Unfortunately I ended up chopping them up and throwing them in the compost bin. I did not realize they may be edible until researching it a week after. However the same location I pulled them up, I have it re-sprouting.

    It would be very cool indeed, if good edible crosses could be made with Oxalis tuberosa. Only concern would be possible high levels of Oxalic acid.

  4. I had another idea today. I was talking about wild relatives of Solanum tuberosum, especially S. acaule which is a cold-tolerant high-altitude growing tetraploid specie. I looked again at the CIP database and I saw high-altitude accessions of several Andean tuberous species, especially Oca and Ulluco. I'm almost sure these accessions would be far more frost tolerant if they grow in some very hostile places such as Altiplano or higher, where the temperatures can drop at -20°C some winter nights. In this case, they may not be earlier but we could be sure they wouldn't freeze when the first light frosts arrive.