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.