Oca: Where Have All the Flowers Gone?

Over at the Radix Root Crops Facebook page, we've been gathering data on when and where oca plants have been flowering this season.  No need to be dragged into the social media maelstrom to contribute - you can post comments here on how your ocas are doing.  Then again, if you'd like to chip in - please do so.

It certainly appears that, with the right combination of stylar morphs, it is not too difficult to achieve pollination and seed set in Oxalis tuberosa. But first you've got to get the plants to flower.  That seems to be a little bit more challenging.

I derive no pleasure from reporting that, with the exception of Ian at Growing Oca's early flush of flowers in June, I seem to be the only person I know who has had flowering ocas so far this year.  In this area of the planet, at least.  I would be delighted if you, dear reader, would be so kind as to prove me wrong.

Some of my plants have been flowering for several months and are forming pods. Indeed, I have been collecting ripe seeds for some weeks already  As flattering as it might be to promote myself as a horticultural genius, I'm really not some sort of oca uber-propagator. No, some other factors must be involved in my  success.  The question is, which ones?

One observation is that big, tall, leafy plants with thick stems seem to come into flower more quickly than those which are smaller.  As usual, there seem to be exceptions to this rule.  Some of my more majestic specimens now have stems of close to a metre in length.  Seedlings with small leaves and short stems, like the one to the right of this picture, seem to be showing no intention of flowering.  I really ought to uproot them immediately, but I'm hesitating; not a case of clemency so much as curiosity: I want to know whether these scrawny runts will perk up when short days come.  Then I'll kill them. Any oca plant that can't enjoy our long balmy summer evenings really has forfeit the right to continued existence and must be catapulted to that heavenly altiplano wherin its ancestors dwell.  Alternatively I might just eat them.

Another observation is that seedlings seem to flower more profusely and earlier than tuber-derived plants.  This could be due to the debilitating effects of accumulated viruses, or a genetic tendency that only surfaces when the plants are grown from tubers - somehow linked to physiological maturity of tuber-derived plants; a similar phenomenon is often found in seedling potatoes versus their tuberous brethren.

Ian at Growing Oca suggests that rather than size, rate of growth might be a contributory factor.  Some of his plants started flowering during a period of moist weather and mild temperatures, then the hot weather and water stress set in, the plants were stunted and no more flowers were produced.  Could be.  I've certainly noticed that flowers on some seedlings seem to abort in the bud stage more readily than others.  I haven't the faintest idea why.

If my experience is anything to go by, daylength doesn't seem to be an overriding factor,  as some of my plants began flowering way back in June, when days were about as long as they ever get.

My understanding is that in the Andes, oca plants grow, flower and then die back to the tubers: they complete their whole life cycle before harvest occurs.  Here, the plants seem to continue growing during declining daylengths until they're zapped by frost.  As enjoyable as it is to be harvesting tubers so late in the season, yields are often disappointing.  My guess is that very short days, low solar intensity and low temperatures are not conducive to producing bulky crops of tubers.  No, we need ocas that tuberise at a more appropriate time of year.  Whether flowering, which in potatoes is usually associated with the start of tuber formation, is a similar indicator of incipient tuber development in oca, I don't know.  My plants have got so big and lush and tangled, it's virtually impossible for me to tell.

One final observation: I noticed yesterday that one of the self-sown seedlings has, in the axils of its leaves, the first signs of flower buds.  Whether or not these will develop and flower before winter comes, I don't know, but it is at least indicative of the possibility of sowing oca seeds directly and standing a chance of securing another seed crop.

So to conclude, my oca flowers haven't gone anywhere - they're still being produced in large quantities.  I'm just a tad perplexed that no-one else has been so lucky.


Ryan said…
It's my first year growing Oca and I think mine have all flowered. They might have a few left too. I didn't know that this was something that people watched?

I'll have to take a pic for the blog!

Thanks for that.

Rhizowen said…
Hallelujah Ryan - I knew someone else must have had flowers by now!

Oca watching - it's the new big thing on Facebook

When you say all - do you have several varieties? If so check for pod formation. Are they in the ground, pots, long stems, short stems?

IAP said…
Still no flowers here.
Ryan, the first thing I did when I read your comment was check your location. Wales. This reinforces my theory that weather is the l factor. I visualise oca in their native Andes bathed in low cloud formed as moist air is forced up over the mountains. Air humidity could be the key.
No flowers here this year either. I only had a very few last year though.
Simon S said…
Oca has just started flowering coincidentally at around the same time as tomato/potato blight has kicked in.
Maybe not a coincidence.

Location SM7 (Surrey/London borders)
It's my first year and I had flowers too, plenty and with different style morph. They started in mid June shortly after I planted them (Carl's tubers), and there was a last flush last week. Tried to hand pollinate, but haven't seen any pods. If you need more precise dates, I can dig out pictures.
Anonymous said…
Any thoughts on the related oxalis crassipes? It's quite popular as a garden flower here in Texas, and is easy to propagate via the tubers at the base. Could it be a good ornamental edible as well?
Rhizowen said…

Oxalis crassipes is, I believe, a form of O. articulata, which is sometimes naturalised in Europe. I have seen it here on many occasions, usually near gardens. I've never tried the 'bulbs', but the leaves are known to be edible. Next time I find a plant, I'll try its subterranean offerings.