Oca as a Late-Planted Crop… Seems to Work

Most growers start their oca tubers in pots indoors as early as possible, and move them outside to their final planting site as soon as the threat of frost has passed. This gives the longest available growing season, and hence more foliage with which to make more tubers. This is quite logical, but oca grows slowly in Spring, and quickly in late Summer, so the question arises - why squander valuable Spring planting space on widely spaced small plants? Why not treat Oca as a late-planted follow-on crop utilising space made available by the harvest of Spring crops? Worth a try I thought, so these plants…

... were held in modules until the beginning of August when a crop of garlic was cleared to make space for them.

Here they are on the 28th of October...

...less than three months after planting out, having seemingly made up for the late start. The yacon (another slow-starting crop) were planted at the same time.
During November, there were a few mild frosts, but the killing frost came on 10th December...

…followed by an unusually wet and stormy winter, which meant that harvest was delayed until early March. Rather late, so I was expecting the voles to have polished off most of the crop, but actually...

…most plants have done no worse than those planted at the conventional time. Maybe the voles drowned this year.

I have to conclude that there is probably little benefit in the labour-intensive business of starting plants early under cover. The fact that oca tubers survive prolonged storage, and are resilient enough after sprouting, means that it is not even necessary to hold the tubers in chilled conditions until the chosen planting time.
With yield apparently unaffected by early August planting, the crop can comfortably follow or relay with overwintered Alliums, Brassicas or roots, early potatoes, peas, or green manure crops.

That's one less thing to do in the April rush.

Skirret—Growing, Selecting (and Eating)

I grew skirret from two sources last year; seed from a commercial supplier, and a few root-cuttings presumably from plants which had already received some selection.

Seed-grown plants are highly variable, and give the chance to select for larger root production, so rather than lift the plants piecemeal as required for the kitchen, I'm checking the whole crop to choose and propagate from the best.
About two dozen plants...

…showing wide variation in quality and productivity...

... those with the thickest and largest roots are used for division. Skirret crowns conveniently provide ready-rooted shoots which can be split off...

…ready for potting up or planting out directly...

Apart from being easy to propagate, skirret has a lot else going for it. To my taste, this is one of the best flavoured and textured vegetables I've eaten; sweet and floury, with more character than say potato or parsnip.
It's perennial, easy to grow, showing no sign of pest damage, tolerates rough weather, and produces attractive flowers and ample seed. In my experience, it stores well simply left in the ground until needed.  With all this, it seems sad that it has almost disappeared from the vegetable garden just because it's a little fiddly to clean compared with potatoes or carrots.

There are varied ideas about the best way grow the crop, but I sowed indoors at the end of April, transplanted the strongest seedlings to modules, and planted outdoors promptly to avoid any risk of amusingly shaped roots. I used block planting, spaced at 12" on a bed of silty soil in full sun, and mulched with 4" of raw woodchippings. During mid Summer they got a sprinkling of wood ash, and a little dilute nitrogen feed. During dry spells, they got perhaps 2gal of water per sq.m/week.

I can also see potential for my now improved stock in a polyculture system, perhaps with alliums, as the two are active at different ends of the year, but I need to experiment more with basic cultural conditions first before I start getting too creative.

- And not forgetting the taste test...

…mmm, farinaceous!
Many reports mention skirret roots having a woody core, but I've seen no instances of this in my harvest, and suspect it may be due to cultural conditions, perhaps lack of water.

There is a recipe for an impressive Skirret Pie here, and more about growing the crop here at The Backyard Larder Blog, and here at Wetting the Beds.

Oca True Seed Progress.

What little true seed that I managed to collect last autumn was sown in mid March, and here is the result so far...

...not a flush, but a long slow ongoing trickle of germinating seedlings. The difference this year, is that I surface sowed the seed, and it seems to have improved success, with the first emerging after four weeks, and no end in sight so far at ten weeks. They had artificial heat to start with, but for the last six weeks have been in an unheated greenhouse, with temperatures oscillating wildly from over 30°C to near freezing. Who am I to know, maybe this is helping.

Meanwhile, last year's true seed success story, IOW2, gets its first chance to grow from tubers. Here it is about to be planted out amongst the outdoor cordon tomatoes.

The soil is still very poor, but we'll see how they do.

Incidentally, I've settled on a quick and easy overwinter storage method for tubers; in autumn I just drop them into multicell trays, add dry compost on top, and leave them to it. It makes sense when there are lots of varieties to keep track of, since the cells can easily be labeled, and it's a simple matter to just start watering when shoots emerge, and they turn into plug plants...

Checking and Storing Oca Seed Tubers

A typical Oca harvest is a bit like a '60s Terry Thomas film -  sure to contain the odd rotter.
Oca tubers contain natural fungicides, and have good resistance to moulds and rots, but if they have been exposed to frost there is no escaping the fact that they are doomed to smelly putrefaction (have a look), and while most of the obvious casualties will have been spotted early when the tubers were lifted and washed, there are usually a few with minor damage that sneak through.
So now, a week or two after harvest, it's time to recheck stocks for any smelly surprises before storing them away until Spring.

And yes, several tubers (those on the plate) needed to be binned. If I had been desperate, I could have sliced off the affected parts, dipped the cut surface in wood ash, and the remaining material would probably have been fine for storing and replanting, but I'm in the fortunate position of having enough tubers.

As I sorted through, I was also carefully checking for any colour mutations, and when I saw the tuber below, just for a second I thought I had the potential to propagate a piebald strain.

Superficially, it looked like the area around one of the eyes had mutated to have black skin -  similar to the black Oca I obtained in the autumn.

But then I spotted an entry-hole leading to this tunnel. I think it's probably wireworm damage. I did notice one making a swim for it when I was washing the tubers.




With all the baddies removed, It's just a matter of selecting the good sized tubers, and putting them into storage. I use egg boxes (with lids closed to reduce drying out) as it helps to keep things organised, and makes occasional inspection easy...

...but the tubers seem to remain viable no matter how badly they are stored over winter; if left uncovered in a  heated room, they will shrivel up, but they will still sprout when the time is right.
If you are fussy about maintaining the visual appearance of the tubers, then aim to reduce the rate of moisture loss, for example by wrapping in newspaper, or a paper bag, or covering with almost-dry sand or sawdust, and placing them in an unheated room, or frost-free shed.
Be aware that if you go for the shed option, mice can develop a taste for them.

I'll start checking for shoots sprouting around late March.

Propagating Oca from Slips & Cuttings

Back in September I was lucky enough to receive a black Oca tuber brought from Lima. It was determined to sprout, having just been whisked away from Peruvian springtime, and despite being stashed in dry sand at low temperature to try to hold it through the winter, the tuber took a while to get the idea, and in the mean time produced several long shoots. Although unintended, once the situation arose, the propagation opportunity was just too good to miss.

'Slips' can be taken in a similar way as with sweet potatoes.
Roots start to develop from the Oca tuber itself, but what makes this method so easy is that roots also tend to form spontaneously at the base of the shoots if they are in contact with soil. It's a simple matter to gently break away the shoot, roots and all, and install it in some sandy compost.

Add gentle warmth, and after a couple of weeks the plants are growing away.

It's an easy way to multiply up a particular cultivar before the start of the growing season.
Placing the tuber in just-damp sand with some warmth during late winter should encourage the rooted shoots to appear.


Incidentally, cuttings taken from growing stems are also very easy and reliable. A large cutting taken as late as September will even be able to form a few small tubers before the frost arrives.
To give an idea of Oca's vegetative powers, I've seen diseased stems that have been completely rotted through near their base (photo here), collapse on to the soil, put down new roots and recover unaided to form a new plant. So no need for hormone rooting compound here!