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How to grow Oca in the vegetable garden

The tubers of Oxalis tuberosa or Oca.
The tubers of Oxalis tuberosa or Oca.
Eric Hunt, Wikimedia commons

Want something new and unusual to try in your vegetable garden this year? Want to make some money on a new crop that foodies are focusing on? Try Oca, (Oxalis tuberosa) a root vegetable from South America, the country that gave us potatoes. As a bonus the plant with its shamrock like leaves and little yellow flowers can be quite pretty.

In the Andes Mountains of Peru the natives grow more than potatoes. They also grow Oca, a plant cultivated and modified by selection for so long it no longer exists in the wild. Like potatoes the stems of Oca swell and make small tubers underground, which are harvested for food. The tubers come in a wide range of colors like the potatoes of the Andes, varying from purple to white. There are said to be different flavors associated with different colors, some being sweeter than others. The leaves of Oca are also eaten like spinach when they are young.

In the 1800’s Oca was introduced to New Zealand where several varieties are now grown as commercial crops. It’s found in supermarkets there in the fall. Oca has been grown in the US and Europe from time to time and was a food craze in the 1830’s for a while. In recent years many gourmand chefs have been featuring Oca in recipes and demand is growing for the vegetable. In Mexico raw Oca is sliced and served with lemon and hot sauce as a tasty appetizer. Chefs are using Oca to add zing to sautéed and stir fried dishes.

About Oca

Oca is about the size and shape of small potatoes, generally longer than they are wide , about 3-4 inches long. They have a thin tender skin that doesn’t need to be peeled. They are high in an easily digestible starch, vitamin C and iron and contain some protein. They also have oxalic acid, (also found in Rhubarb) the concentration of which varies depending on the variety. For this reason people with gout or prone to kidney stones may want to avoid Oca.

Oca is said to vary in taste depending on variety. Some are sweet tasting, some have a tart lemony taste, some are blander and starchy like potatoes. They are cooked in all the ways potatoes are cooked and are also eaten raw. Oca can be sun dried which concentrates sugars and the right varieties are said to taste as sweet as dates when dried. One named variety from New Zealand ‘Apricot’ is said to taste like its name. The leaves and flowers are used in salads and the leaves are also cooked like spinach.

How to grow Oca

Oca can be started from seed but that is difficult and like potatoes they are usually grown from tubers saved from the last season. In practice pieces of tuber or small tubers are generally left in the ground during harvest and will return the next season. ( It is not known how well they survive in the ground in planting zones lower than 7.) They will slowly increase in a garden setting but are not as invasive as Jerusalem artichokes.

Oca tubers are planted like potatoes in rows or mounds 18-24 inches apart. Plant when the soil is moderately warm and heavy frost is no longer expected, just like potatoes. They can have soil pulled up around the stems two or three times to increase the amount of stem underground that will form tubers. Oca plants have clover like leaves and form bushy plants about a foot high. They need full sun and fertile, well-drained soil. Like potatoes they do not tolerate drought well and will need to be watered when it’s dry.

Tubers are harvested after the tops are killed by frost. They can be left in the ground until just before the ground freezes. Sun curing for a few days after harvest is recommended. Tubers become sweeter during storage. They store about as well as potatoes and should be kept in a cool dark place.

Challenges to growing Oca

While Oca could be an interesting, even lucrative crop to grow there are some challenges. Oca is a perennial plant. The plants need a fairly long frost free season to grow and while the plants may survive in colder climates the tubers start growing when days are less than 12 hours long and stop growing at a heavy frost which kills the foliage. That means in a zone 6 climate the plants would begin forming tubers in September but if there is an early frost they might not have time to produce many tubers. The suggestion here would be to add low or high plastic tunnels before a heavy frost is predicted or to grow them in tunnels in planting zones lower than 7.

Another challenge is finding planting stock. Few varieties are available. Potted plants are usually sold and they are expensive compared to potato sets. Territorial Seed company sells potted plants. A couple of well cared for Oca plants should give you a harvest of many tubers that could be planted the following year. Producing planting stock to sell might net you more profit than producing tubers for cooking.

While many trendy chefs are using Oca in recipes, sales could be slow outside of major cities unless one develops a market with local chefs or foodies. But if you just want something unusual to offer at a farmers market or just want to try something different for your own dinner a few Oca plants might be just the thing this spring.

Here are some additional articles you may want to read.

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How to grow and use Chicory

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