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...

This Oca Relative Tastes Better than Oca!

Here's another Oxalis weed which has arrived on the plot.

I only took notice of it when I dug it out with a trowel during some detailed weeding. It had a substantial (for the size of the plant) tuber. Having a curious nature, I washed it and tasted a corner. It tasted good, so I munched the whole thing. It tasted sweet, moist, succulent, and had no hint of oxalic acid.
I've already mentioned Creeping Woodsorrel (Oxalis corniculata) which was easily identifiable by its bronze foliage, but I'm not absolutely sure what this one is. Checking a guide to wild flowers, I think the most likely candidate, given the dark pink flower and the cluster of bulbils, is Oxalis corymbosa, the Lilac Oxalis (but there seem to be several common names). A bit of research told me that it is another native of South America, now naturalised in the south of the UK.
The taste really is very good, but the tuber just needs to be a bit bigger to be worth harvesting. Given a bit of selection coupled with good cultural conditions,  this could perhaps be a useful easy-to-grow ground-cover crop for use in polycultures. It certainly seems to do well in quite deep shade, so it would work well with say, tall brassicas
I will look out for more, and give them a corner to themselves to see what happens. Perhaps if allowed to grow for more than one season the tuber will get bigger.

Update: My later post about this plant.

Some information on Oxalis corymbosa, and Oxalis corniculata here.
The Pfaf database also has an entry for this plant.