It is cultivated as a root vegetable in the Andean region, at cold, windy altitudes above 2700 meters. The above-ground portion dies back with frost, but the root is quite hardy. It grows to a height of 1 meter, and bears edible tuberous roots that can reach the size of a man’s forearm, with a dry weight composition of about 7% protein and 87% carbohydrate. Yield can reach 50,000 kg/ha given two years maturation time. Great interest in this root crop has been generated by its ability to be grown in conditions that do not favor other root crops.
The roots of some forms if eaten directly can irritate the mucus membranes, and should be sun-dried and boiled before eating to eliminate the irritating substance. Bolivian forms are more often irritating than Ecuadoran forms. The cooking water of the M. expansa makes a satisfying sweet drink while leaves may also be eaten as a leaf vegetable or used raw in salads. Once the root has been exposed to the sun the astringent, bitter taste is replaced with sweetness. One of the traditional preparations the boiled roots are mixed with honey and toasted grain. Ecuadorians have both sweet and salty preparations.
Mirabilis expansa was an important root crop to the Inca empire and was considered a “lost” crop until being rediscovered in the 1960’s and 1970’s in three separate distant locations in Peru, Ecuador and Bolivia. There is a possibility that the plant’s continued use and survival in three separate locations was due to the Inca policy of transplanting valuable food crops and communities throughout the empire.
The stems are cylindrical and are divided by nodes, from which pairs of opposite leaves arise. The leaves are ovulate or cordate, 3 to 8 cm long, 2 cm wide and somewhat coriaceous. The nervures and edges have reddish areas. The inflorescences are on long, slender terminal branches, are 3 to 6 cm in length and are covered with hairs which frequently have small insects stuck to them.
The stems are salmon-pink in colour when they are below ground. They are generally smooth and fleshy, up to 50 cm long and 5 cm wide. The swelling process of the stems and the accumulation of nutritive substances are typical of Nyctaginaceae; they are the result of cambium activity creating irregular peripheral tissues around the external part of the stem. Towards the centre, several elliptical rows of isolated xylem vessels may be seen. The basic tissue is parenchymatous with an abundance of water, many starch grains and some cream-colored.