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...

'Minor' Root Crops as Ground-Cover in Polycultures

Oca can provide extremely effective ground-cover within a vegetable polyculture, as demonstrated with tomatoes, or sweetcorn. But how about using other minor root crops in the same role?
Ulluco  for example...

Sprouting Ulluco tubers lifted from storage in sand, 15th March.

... and Chinese artichoke (below) both give cover earlier in the growing season, lasting through to the first frost. And being very definitely 'minor' in productivity, I can't justify either of them as a monocrop; my basic criterion is that bed-space must produce a decent kitchenable yield, preferably with the minimum of labour.

Chinese artichoke tubers

But even if they don't produce much crop, at least they can reduce my weeding and watering by acting as a living mulch around other more productive crops .
I'm going to give them both a try growing with climbing French beans, plus garlic and elephant garlic.

Last autumn the bean-bed-to-be was cleared too late to establish an overwintering green-manure crop, so without digging, I planted it with garlic and elephant garlic, then added autumn leaves, retained with steel mesh. Here's the scene in late winter...

In early April the mesh is removed, and the ulluco and Chi-chokes (previously started in pots in an unheated greenhouse) are added between the garlic. Plastic sheet is placed down the centre of the bed to warm the soil for the beans.

Pot-grown Chinese artichokes planted out, 3rd April

Initially, there's a lot of slug-damage to the ulluco, especially those with green stems. The red colouration of some varieties seems to offer protection against pest damage.

Slug-damaged ulluco, 15th April

Removing the plastic sheet, allowing access to foraging birds, seems to improve matters.

Bellow, supports added in readiness for the French beans. The weather is hot and dry, so the mulch is topped up with a layer of grass cuttings.

5th of May, (below) the French beans, started previously indoors in root-trainers, are planted out.

French beans added, 5th May

Just after the photo was taken I pinched out the tips of the Chinese artichokes to encourage more side growth. There's no sign of any weeds getting through the autumn leaves yet (apart from the odd oca volunteer - which will be tolerated for now).

All done! If the ground-cover crops expand to give full cover before the leaf mulch breaks down, then there should be no more work involved apart from harvesting. My one concern is that there may be excessive competition for moisture between the crops if there is a dry summer, but we shall see.

Update 9th June. First produce from the system is garlic...

... no complaints there.

Meanwhile, the beans are twining, and the ground cover is closing up well...

The Chi-chokes have just about reached full cover, but the Ulluco are slightly slower.

Update 30th June.  Next — the elephant garlic has died back, so harvest time:

Some have only formed rounds rather than cloves, probably as they were slightly late getting planted. Lifting them caused a bit of disturbance to the Chi-chokes' roots, but hopefully no serious harm done.

Update 3rd August. The beans have been cropping well for about four weeks. The ground cover is complete, and virtually no weeds have made it through.

Update 22nd November. The beans and their supports have been removed. The first picking of tubers, a square foot of the bed, delivers enough Chinese Artichokes for a meal...

 I feel a stir fry coming on.

Update 16th January. I'm continuing to lift tubers as they are needed in the kitchen. As you can see there are plenty of volunteer Oca to be had amongst the Chinese artichokes...

The Ulluco have now been killed by frost, so I'm also lifting them now. They've done better than last year, but that's not saying much.

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Oca — Sprouting and Ready to Go

If these tubers could talk, they'd shout "plant us!"

Usually I have them starting in pots in the greenhouse by this time of year, but I've been busy, and as a result they've been sitting in storage, in an orderly but impatient manner in their egg boxes...
 

That's a lot of varieties to fit in to my available growing space.  I had a rough planting plan in my head, and felt it would all be fine at a squeeze, but then last week I received a package from Frank Van Keirsblick containing a further seventeen new varieties, all neatly bagged and labeled, from his breeding programme.
This was good because I now have greatly improved crossing potential with so many varieties increasing the chances of compatible flower forms, but I'm going to have to rethink the grand plan to accommodate all of these extra plants.

With Frank's, plus four each of my existing varieties totaling about 70 plants, there are going to have to be some logistical cut-backs too; greenhouse-space, pots, compost, are all in short supply. I'd like to plant out direct, but the ground is not prepared yet, so I'll try a method less extravagant than individual 4" pots.
I've packed 64 tubers into two root-trainer trays. They should be fine for a couple of weeks, and take up very little space in the mean time.

One set of venetian blinds later, Frank's varieties are labeled up...

... and order is maintained - so far.