Learn how to grow oca. Oca is a highly productive perennial plant with waxy, brightly colored tubers that are perfect as a season-extending crop. It is an excellent source of carbohydrates, phosphorus and iron, as well as essential amino acids that promote the health and proper function of muscles, organs, nails, hair, skin and more. Originally published as "You Can Grow Oca!" August/September 2007 MOTHER EARTH NEWS.