Yams (Oca)

Yams grown in New Zealand originate from the South American Andes where they are known as Oca (Oxalis tuberosa).  They are related to that pesky week Oxalis and Irish Wood Sorrel (the Shamrock).

South American in origin, these tubers which we refer to as Yams but are in fact called Oca, were brought to Europe in the 1830s, apparently as a potato alternative, then made their way from there to New Zealand around 1860.  Interestingly though it was not until the 1980s that Oca was first grown on a commercial scale and thus introduced to North Islanders who had been missing out on this winter delight.

The sweet tubers are small, often about the size of a thumb, and can be pink-orange, yellow, apricot and golden in colour, slightly shiny and ribbed surface.

NOTE: New Zealand yams are different from the tropical yams grown in other cultures. In America, and therefore in American recipe books, the vegetables known as ‘yams’ are in fact sweet potatoes similar to Beauregard kumara.

What to look for

Firm yams with a bright colour and no blemishes.


April, May, June, July, August, September, October.

Ways to eat

Yams are eaten cooked and in this form the carotenoids are more available. Boiling or steaming minimises their oxalate levels. Serve whole or mashed. Use sliced in stir fries. The natural sweetness of yams is enhanced with ginger, orange or sweet and sour sauces.

Suggested cooking methods

Bake, braise, boil, steam, microwave, roast, stir fry, stew.


Yams are one of the highest vegetable sources of carbohydrate and energy (kilojoules). They are a good source of folate, a source of vitamin A (from beta-carotene) and vitamin B6 and contain potassium at levels of dietary significance.

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