What is Oka? Do you mean OKRA? If so, I've grown it in years past, and it was very productive.

No, it's oca. I don't know anyone who's grown it, though:

Here is a link that might be useful: how to grow oca

A few years back a friend gave some tubers, they were planted in the spring and they were growing nice in the beginning but after we got hit with the heat and the humidity, they were starting to decline. I was growing them in a fabric potato bag, maybe if I was growing them in the soil and in shade I might have a different result since they are grown at high altitudes and temperate climates I really don't know.
And if you have not tried them yourself, you might not even like them. They are not on top of my favorite list.:)

Silvia