How to Grow South American Oca

by Shelby Baker

While not yet well known, oca plants are slowly shooting up in home gardens in North America. The little tubers, also known as New Zealand Yams, are actually native to South America. Thousands of varieties are grown and harvested throughout the continent-some are capable of thriving in the Andes Mountains, 4,000 meters in elevation. These small yams pack a powerful nutrition punch, containing carbohydrates, phosphorus, and iron, promoting good health.

Oca produces brightly colored tubers in yellow, orange, and red shades with waxy skins, making them a beautiful addition to the garden as well as your plate. The plants grow compactly, typically reaching a foot tall with clover-like leaves. Rather than growing up, the vines of oca will grow outward to establish themselves, boasting edible trumpet flowers.

Growing Conditions for Oca

Oca is extremely sensitive to daylight-the plants won’t produce tubers without at least 12 hours of sunlight a day. They do well in a soil pH of 5.3-7.8, but the ground must be sandy, light, and fertile for tubers to grow. While oca prefers warmer climates with longer days, it does not do well in tropical lowlands or hot, humid climates. In these conditions, oca is likely to develop rot.

Unlike most edible tuber plants, oca holds a special place in gardens as a perennial in warmer climates from San Francisco and farther south. In the Pacific Northwest, the plant will still flourish-but as an annual crop. Make sure to plan accordingly based on geographical location for whether or not oca will need to be replanted each year in your zone.

How to Plant Oca

Fortunately for many home gardeners who’ve grown other tubers, oca acts very similar to potatoes when it comes to planting, care, and harvesting. They are planted from the past harvest’s tubers, which are kept in cool, dry climates.

Oca can either be planted directly into the garden ground or in containers. While container gardening allows earlier planting and more convenient care, oca grown in containers will produce less tubers than specimens planted in the ground due to space. Planting directly into the ground must be done after danger of frost has passed, but this methods has a much higher yield than container gardening. Decide which route is best for your garden beforehand, as oca has a long wait time until harvest, 180-360 days.

Plant the seed tubers three to four inches deep at 12 inches apart, and cover. If the soil is not fertile enough already, add compost or manure to fertilize the area. Water the tubers after planting.

Care of Oca

Water the plants regularly throughout the growing season. If the plants are not receiving at least 12 hours of full sunlight every day, supply artificial light to meet their needs so the tubers will begin to form.

Tubers will begin to appear in September and will grow and ripen during the two to three months prior to the first frost. Just like potatoes, oca needs to be hilled up. Once the plants reach six inches tall, hoe up and shift the dirt around the plant’s base to protect the roots and support the plant. Do this every couple of weeks to protect the plant.

Oca Garden Pests and Diseases

Fortunately for many gardeners, these tubers aren’t typically bothered by pests. Nematodes can prove annoying, but seem to be the only issue thus far. Sadly, oca is popular among animals such as mice, chipmunks and even barn owls for its delectable flavor. Be wary, or you could find nubs where the lush green leaves once were.

While not nearly as susceptible to pests and diseases as potatoes, South American varieties of oca do face some issues with viruses. However, oca tubers in North America are started in nurseries without those viruses present, allowing a fresh start in many home gardens for these plants.

Harvesting and Storing Oca

Harvest takes place in December and January after the frost. Don’t worry too much about the late harvest time. Even after the tops die off, the tubers themselves will survive in the soil so long as the temperature remains above 23 degrees Fahrenheit.

Because the soil is sandy, digging up the tubers should be easy. Make sure to harvest the oca on a dry day. Taking care to delicately pull them up from the ground without puncturing the skins.

Tubers will range from one to five inches long, averaging at three inches. Oca doesn’t require a root cellar, but still they need to be stored in a cool, dark place. To reduce the oxalic acid and sweeten the tubers, keep them in a lightened area for about a week before storing. The tubers will last and be edible for several months after harvesting. Tiny tubers can be stored until ready to propagate for the next planting season.

Ways to Prepare Oca

Oca is a true chameleon in the kitchen. Its flavor ranges across the board, from potatolike to sensations to match the sweet sting of lemons or the brightness of apples. The tubers can be prepared any imaginable way:eat them raw, boiled, baked, steamed, sun-dried, grilled, fried, or candied.

Wash the tubers under warm water and gently scrub them of remaining soil. Because they don’t need to be peeled for use, go dive straight into cooking. Add them to stews and soups, or roast them tossed in lemon juice, salt, and pepper. They can also be used in pies similar to rhubarb, which also contains oxalic acid for a similar flavor profile in cooking.

The flowers and sour leaves of the plant are edible as well. Toss them in a seasonal salad, or wilt the leaves to be served beside a main course.

As a delightful new addition to North American gardens, oca’s uses and growth are still coming to light. The cultivated tuber is a bright and beautiful addition to home vegetable gardens and kitchens. With its long, low-maintenance growing season, this “lost crop of the Incas” yields large, satisfying harvests each year.

Want to learn more about growing oca?

Mother Earth News covers How to Grow Oca
Permaculture covers How to Grow and Store Oca
University of California Master Gardeners of San Mateo and San Francisco explains Growing Andean root crops: Oca
Perennial Vegetables: From Artichokes to Zuiki Taro, A Gardener’s Guide to Over 100 Delicious and Easy to Grow Edible by Eric Toensmeier, pgs 175-176
Potato growing tips from The Old Farmer’s Almanac
Cultivariable covers Andean Root Tubers
Purdue University Extension covers Andean Tuber Crops: Worldwide Potential