I know from reading that oca (Oxalis tuberosa) begins to form tubers around the time of the fall equinox and I know from experience that it forms tubers of good eating size about ten weeks later, but what happens in between? Is the rate of growth of the tubers relatively constant, or does more of it happen early or late in the growth period?  I have enough plants this year that I have been willing to sacrifice a few to find out.  From what I can see, the rate of growth is probably pretty constant, although we’ll have to wait until harvest to know for sure.

Here is the yield of a Sunset oca plant at the equinox.
There was one tiny tuber and the stolons were beginning to swell a little.
Another Sunset oca plant pulled about a month later.
Now we have tubers.
Cleaned up harvest from the plant above.  Tuber weight = 0.4lb / 180g.
Not much of a harvest, but big enough to eat.

In another month, I expect they’ll be twice this size and perhaps up to three times as large by harvest if we have a late enough frost.

It looks like a month after the equinox is enough time to get a reasonable oca harvest.  It won’t compete with other staples at 0.4lb per plant, but it is enough to have a taste and save tubers for the next year.  If this plant had been frost killed, the tubers would still undergo some growth, so yield might amount to half a pound or more.  That seems to bode well for people in less than ideal oca climates who want to try to breed some more suitable varieties.

Update Nov. 4:

Two weeks later a test pull gave a full pound of tubers.

Single Sunset oca plant harvest from Nov. 4
1 pound of tubers with the tiny tubers removed (less than eating size)

Oca seeds and tubers are sometimes available in our seed shop.

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