Sunday, 16 January 2011

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.


  1. thanks a lot for all your pix and detail. the variety I have is very similar to your purple one (right of the last pix), but its color is lighter.

  2. Michael Willcocks19/4/11 3:48 pm

    I dug a third of mine up in late November, mixed white & pink, just after the first frost, not knowing/understanding that they would continue to swell.

    Ate the biggest & dumped the rest in a plastic shopping bag.

    When my partner complained around Christmas about the "tubers in a bag", I moved the bag back to the garden shed & forgot about it.

    First weekend of April I dug up the rest and looked for the bag with the originals.

    Some in the bag had putrified and turned into a black sludge, some had sprouted. I cleaned off the best and planted them in peat pots.

    I’ve potted 40 in total.

    The smallest tubers (re-bagged in plastic shopping bag) look fine & I’ll post them off to my mum this weekend.

    Not all of the smallest have over-wintered in a plastic bag stored in an unheated potting shed, statistically some survived underground.

    But all of them have spent 3 months in some kind of less than ideal storage, so they (Oca) must be a tough plant, well inured to getting through hot/cold dry/wet winters.

  3. I planted oca for the first time this year. I planted in pots and waited for them to sprout. I then planted the out under a netted (enviromesh) tunnel, watered and looked after them as advised although I never earthed them up. I harvested them yesterday and was bitterly disappointed 99per cent of them were the size of a small pea and the others not much larger. I did notice I had some growing up the stems. They hadnt made much root growth and there were hardly any underground. What have I done wrong because they were very healthy large plants until they got frosted.

  4. Many thanks for the information in your blog. My daughter and her partner took over a lovely allotment-style plot with their new house, and we've been perusing these little tubers, wondering what on earth they are.
    I'm thinking we'll have to taste them but feeling a bit nervous as I've never eaten them before. I'm feeling very encouraged by all you've said though :0)