The yacón (Smallanthus sonchifolius) is a species of daisy traditionally grown in the northern and central Andes from Colombia to northern Argentina for its crisp, sweet-tasting, tuberous roots. Another name for yacón is Peruvian ground apple, possibly from the French name of potato, pomme de terre (ground apple). The tuber is composed mostly of water and various polysaccharides.
Description Yacón is a perennial herb that grows up to 2.5 metres (8 feet) tall. The stem is cylindrical to angular and hollow when the plant is mature. Leaves are opposite and deltoid. Their upper surface is hairy. Underground tubers consist of branching rhizomes and up to 20 tuberous storage roots. The rhizomes continually produce leafy shoots, while the storage roots are the principal economic product of the plant. The storage roots are up to 25 centimetres (10 inches) long, 10 cm (4 in) wide, achieving a weight of 0.2–2 kilograms (0.44–4.4 pounds), and have varying skin colours. The colour depends on the variety, and ranges from white to pink to brown. Yacón plants produce small, inconspicuous flowers at the end of the growing season. The timing of flowering strongly depends on the environmental conditions. If environmental conditions are favourable, flowering begins 6–7 months after planting and peaks about two months later. The yellow to orange coloured flower head is a pseudanthium (i.e. one apparent flower head is in reality composed of several florets). Each flower head is bisexual, uniting female and male florets in one pseudanthium. The yellow or orange ray florets are female and up to 12 mm long, while the yellow-brown disc florets are male and about 7 mm long. The seeds are stored inside dark brown achenes averaging 2.2–3.7 mm in length. In general, seed production is rather low; some ecotypes do not produce any seeds at all, due to pollen sterility. Plants produced from seed take longer to mature than do those grown from the tubers or rhizomes. The texture and flavour of the roots are very similar to jícama, 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.
Similar species Yacón is sometimes confused with the unrelated Pachyrhizus erosus (jícama), which is a legume, as yacón is commonly called jícama in Ecuador. Yacón, in contrast, is a close relative of the sunflower and Jerusalem artichoke. 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 as in mountainous regions.
Cultivation
Freezing temperatures cause the above-ground parts to die back; the plant will re-sprout from the rhizome under favourable temperature and moisture conditions. The optimal growing temperature range is 18–25 °C. Yacón can easily be grown in gardens in climates with only light freezes. It grows well in Kathmandu, Nepal, southern Australia (including Tasmania) and in New Zealand, where the climate is mild and the growing season long. The plant was introduced to Japan in the 1980s, and from there its cultivation spread to other Asian countries, notably South Korea, China, and the Philippines, and is now widely available in markets in those countries. Traditionally, yacón roots are grown by farmers at mid-elevations 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. Yacón is also grown on the Atherton tablelands in Queensland. The plant can be grown using either stem cuttings or the purple rhizomes at the base of the stalks. It will not reproduce from the tubers, which, when unharvested, rot in the ground, providing fertilizer for later crops. Outside of its traditional cultivation range, yacon is planted in a well-dug bed in early spring, near the time of the last expected frost. While aerial parts are damaged by freezing temperatures, the tubers are not harmed unless they freeze solid. Yacón is a vigorous grower, much like Jerusalem artichokes. The plants grow best with fertilizer. After the first few freezes, the tops will die and the tuberous storage roots are ready for digging. Perennial rhizomes are left in the ground for propagating the next crop, or, alternatively, they can be kept in a refrigerator or buried away from freezing temperatures until spring.
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