Oca (Oxalis Tuberosa): Lost Plant of the Incas?

You've eaten potatoes, maybe even sweet potatoes, but chances are that you've never tried oca.

No, I don't mean okra! According to Seeds of Change, oca (oxalis tuberosa), like regular potatoes, comes from South America (specifically the Andean region). It was once widely cultivated by the Incas and other South American tribes, and is still eaten there, as well as in Mexico, today. But unlike the potato, oca has never caught on in most of North America.

Why? One reason is that growing oca requires rather specific weather conditions. Green Harvest says that the plants wilt and die in higher temperatures (above about 82° F or 28° C). They also require days with less than 12 hours of sunlight in order to set tubers, and need a couple of frost-free months in the fall for the tubers to grow to their full size. However, says Green Harvest, they will tolerate "a wide range of soil types and pH."

That has restricted oca-growing primarily to areas like the California coast and the Pacific Northwest. And they can't be imported.

So why would you want to grow and/or eat oca anyway?

Well, they taste good both raw and cooked. Oca comes in different varieties. They can be acidic and tangy (due to oxalic acid content), or mild in flavor, similar to new potatoes or sweet potatoes. They can be baked, boiled, fried, mashed with butter and salt, or added to soups and stews. Raw oca is good in salads. Even the leaves can be eaten.

Given the right weather conditions, oca are relatively easy to grow and produce well. According to Lost Crops of the Incas, "oca is easy to propagate, grows luxuriantly, requires little care, and is exceptionally tolerant of harsh climates [i.e., mountainous areas] -under which its yield can be twice that of the potato."

To grow oca, get seed tubers from a nursery in early spring (usually $14-16 per dozen, but each plant will produce 2-3 pounds of oca). You'll plant the whole tuber, rather than cutting them up like one might do with seed potatoes. If your region regularly gets temperatures above 80° F, plant oca in partial shade; otherwise, plant in full sun.

You'll want to hill up soil around the plants every couple of weeks starting around 4 months. The tubers can only form below the soil, so the more you hill up the soil, the more tubers the plant can produce.

Harvest oca when the stems start to die back from cold weather. Seeds of Change says the plants can handle a light frost, but if temperatures drop below 28 degrees Fahrenheit for more than a few hours, they will die back. Oca can then be stored for several months if kept in a cool, dark place (35 to 45° F).

SOURCES
Wikipedia, "Oca", Wikipedia
Frances Michaels, "Oca or NZ yam growing information", Green Harvest
Office of International Affairs, "Lost Crops of the Incas", The National Academies Press
Steve Peters, "Oca -- Food of the Future", Seeds of Change