You Can Grow Oca!
(Page 2 of 4)
August/September 2007
By William Woys Weaver
New Zealanders also have undertaken the most thorough nutritional analysis of oca to date. Like beets, spinach and rhubarb, oca contains oxalic acid, which can be harmful to the urinary tract if ingested in large amounts. According to Purdue University, however, oca actually has less oxalic acid than spinach, and one would have to eat nothing but oca to experience any harmful effects. Furthermore, most of the oxalates in oca are water-soluble, which means all you have to do is boil or steam it and pour off the water. And when left in the sun for a few days, several varieties will undergo a chemical change in which some of the acidic elements are converted to sugars.
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To play it safe, anyone who has an allergic reaction to rhubarb, sorrel, beet greens or spinach, or anyone suffering from gout or kidney stones, might want to avoid oca.
OCA AS A GARDEN CROP
Oca is day length sensitive (even the New Zealand varieties) and will not tuberize until there are less than 12 hours of light per day. For most of the United States, this means the tubers won’t begin to form until November, so keep them well covered and free of frost until Christmas, or raise them in plastic-covered tunnels with some sort of minimal heating arrangement so the tops don’t freeze.
Oca is propagated from tubers, so it’s cloned in a manner similar to potatoes. It prefers sandy soil, partial shade and cool, damp weather. Plant whole tubers in pots in late winter (mid-March is my method), and once they form healthy vines, transfer them to tubs or into the ground after the threat of frost has passed. Planting at this early date is important because the plants must be well established before hot weather sets in. They don’t tolerate hot sun and a hard drought certainly will kill them unless they’re well watered. To avoid these problems, I plant mine in tubs, which I move into a greenhouse so the plants can run their course. They die back naturally in January, which is when I harvest the tubers.
A sandy cactus potting mix seems to work best as soil, and they must be fed heavily, especially in September and October. They have no known pests, at least not in North America, which is a plus for organic growers. However, mice, barn rats and chipmunks are quite fond of oca, and I’ve had voles chew their way through the bottom of my tubs to steal the tubers.
Tub culture is convenient, but the plants don’t produce as many tubers as they would in open ground. In open ground or in tunnels, you can triple tuberization: Layer and bury the rubbery stems (which often reach 2 feet in length) just beneath the surface so tubers will form around the buried stem sections. Tubers also will form along the underside of stems that touch the ground.
