The All-Tuber Polyculture Mound, Part 2 ... Room for One More

A previous post showed how last year I used mound culture to grow a mixed tuber crop (Yacon, Oca, and Chinese artichokes) with the minimum of labour input.

Here's what's left of the mound... 

...untouched since last December when it was torn open to yield over 20 lb of harvest.  As I anticipated, there are plenty of volunteer Oca and Chinese artichokes appearing amongst the annual weeds this year, so I only need to add a Yacon to restore last year's successful system.

Less than five minutes after the previous photo...

... and the weeds are blotted out by a heavy covering of garden compost, and a pot-started Yacon is added to the top of the heap.

This much compost might seem like an extravagance, until one thinks back to the amount of biomass which was removed at harvest; here's the near hernia-inducing Yacon root as a reminder...

I'm also adding a fourth member to the polyculture. The Hog Peanut, or Talet (Amphicarpaea bracteata) is not a true tuber-crop, so stretches the concept slightly,  but will clamber and twine amongst the Yacon, potentially fix nitrogen, and hopefully add to the overall interest and subterranean yield of the mound with its wacky underground beans.

It's another self-propagator by all reports, so like the Oca and Chinese artichokes, it should be back every year...

...whether I like it or not.

Update photo, 1st August...  ...five foot high an' risin'.

The Trouble with Arracacha...

I previously announced my successful overwintering of Arracacha cuttings.
So by now I should have the stout healthy specimens established outdoors, perhaps just flicking off the odd aphid, or casually hoiking an occasional weed from their mulch. But in fact they are still in pots, and under intensive care.
So what is the trouble? Well, I've been up some blind alleys trying to answer that. I noticed dieback of parts of the root system, along with yellowing then death of older leaves. Here's one plant during an unsuccessful examination for root-eating wildlife.

Here's a shot showing leaves at the stage after yellowing...

...Next comes complete death of the leaf. My guess is that the original cuttings carried some virus with them from Brasil, and given that the plants are now dropping leaves as fast as they grow new ones, I'm loosing hope of getting a crop this year. I should probably cut my losses and burn the remaining survivors.

But there is another approach...

A couple of plants have been determined to flower since mid winter.  The photo above shows the umbel-mounted tiny flowers in various stages of doing their thing.
If the plants stay alive long enough for the seed to become viable, this might give a route that leaves any virus behind, and give some plant variation, with all of the benefits that brings.

So probably no Arracach fritters this year then.

Update. All plants died by Spring. Darn it!

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...