Yacon – Smallanthus sonchifolius

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The yacón (Smallanthus sonchifolius, syn.: Polymnia edulis, P. sonchifolia) is a species of perennial daisy traditionally grown in the northern and central Andes from Colombia to northern Argentina for its crisp, sweet-tasting, tuberous roots. Their texture and flavour are very similar to jicama, mainly differing in that yacón has some slightly sweet, resinous, and floral (similar to violet) undertones to its flavour, probably due to the presence of inulin, which produces the sweet taste of the roots of elecampane, as well. The tuber is composed mostly of water and fructooligosaccharide.

The yacón, in contrast, is a close relative of the sunflower and Jerusalem artichoke. The plant produces a perennial rhizome to which are attached the edible, succulent storage roots, the principal economic product of the plant. The rhizome develops just under the surface of the soil and continuously produces aerial shoots. Dry and/or cold seasons cause the aerial shoots to die back, but the plant resprouts from the rhizome under favourable conditions of temperature and moisture. The edible storage tubers are large and typically weigh from a few hundred grams to a kilogram or so.

The tubers contain fructooligosaccharide, an indigestible polysaccharide made up of fructose. Fructooligosaccharides taste sweet, but pass through the human digestive tract unmetabolised, hence have very little caloric value. Moreover, fructooligosaccharides have a prebiotic effect, meaning they are used by beneficial bacteria that enhance colon health and aid digestion.

Yacón plants can grow to over 2 m in height and produce small, inconspicuous yellow flowers at the end of the growing season. Unlike many other root vegetables domesticated by the indigenous peoples of the Andes (ulluco, oca, and mashua), yacón is not photoperiod sensitive, and can produce a commercial yield in the subtropics, as well.

Traditionally, yacón roots are grown by farmers at midelevations on the eastern slopes of the Andes descending toward the Amazon. It is grown occasionally along field borders where the juicy tubers provide a welcome source of refreshment during field work. Until as recently as the early 2000s, yacón was hardly known outside of its limited native range, and was not available from urban markets; however, press reports of its use in Japan for its purported antihyperglycemic properties made the crop more widely known in Lima and other Peruvian cities. Companies have also developed novel products such as yacón syrup and yacón tea. Both products are popular among diabetics and dieters.

Yacón can easily be grown in kitchen gardens in climates with only gentle frosts.

Propagation roots with growing points can be planted in a well-dug bed in early spring, near the time of the last expected frost. While aerial parts are damaged by frost, the roots are not harmed unless they freeze solid. Yacón is a vigorous grower much like Jerusalem artichokes. The plants grow best with fertilisation.

After the first few frosts, the tops will die and the roots are ready for digging. It is generally best to leave some in the ground for propagating the following spring, or, alternatively, they can be kept in the refrigerator or buried away from frost until spring. While usable-sized tubers develop fairly early in the season, they taste much sweeter after they have matured and have been exposed to some frost.

The leaves of the yacón contain quantities of protocatechuic, chlorogenic, caffeic, and ferulic acids, which gives tisanes made from the leaves prebiotic and antioxidant properties.