BOTANICAL NAME: Smallanthus sonchifolius (formerly Polymnia sonchifolia)
COMMON NAMES: Yacon, Peruvian ground apple, Bolivian sunroot, llacon, groundpear, pear of the earth.
It is comparable to the white fleshed tuber Jicama /Climbing Yam Bean – Pachyrhizus erosus.
Yacon is native to South America and is a hardy, attractive herbaceous perennial that yields a large harvest of tubers. As a member of the sunflower family, yacon can grow to 2 metres/6 foot in height with small, male and female, daisy-like yellow flowers.
FAVOURITE GROWING CONDITIONS
Prepare the soil by loosening well with a fork and working in compost. To plant, cover a large rhizome which has several sprouts, with soil to a depth of 3 cm. Mulch well, yacon will grow up through the mulch, just like potatoes. Little weeding is needed because of the dense shade created by their huge leaves. Yacon can be planted all year round in frost-free areas as it is day-length neutral. It appears to be drought tolerant compared to other vegetable crops and so far, pest-free.
NB For cold areas of Australia the rhizomes can be started in styrofoam boxes in a greenhouse or on a warm verandah and planted out when frost is past.
Plants grow quite large and vigorous, so space them at about 0.5 metres apart. Yacon grows fast even in poor soils but crops best in rich, friable, well-drained soil. Yacon actually produces two types of underground tubers, reddish rhizomes directly at the base of the stem, which can be eaten when young but are mainly used for propagation. The larger brown tubers store well and are for eating.
Separate the reddish rhizomes from the plant base with a knife and gently wash off any soil. The reddish rhizomes are kept out of the sun and covered with slightly damp cocopeat or hessian to stop them drying out and put aside, in a dark, dry place. As soon as the rhizomes begin to sprout, this can be between 5 – 30 days depending on conditions, it is time to plant.
The plant takes 6 – 7 months to reach maturity. After flowering top growth withers and dies back and the tubers are harvested. Dig carefully around the base of the plant to avoid damage to the crisp tubers. They resemble dahlia or sweet potato tubers, on average weigh about 300 g but can weigh up to 2 kg. Once the soil starts to heave at the base of the plant, dig around to ‘bandicoot’ a few early tubers to extend the harvest season. The tubers continue to sweeten as the plant dies back so the main harvest should only take place once all the top growth is dead, between May and July depending on mildness of the winter. Don’t leave harvesting too long during mild winters as the new red tubers will start to shoot again as the soil warms up.
After separation from the central stem undamaged small red tubers can be stored in a cool, dark and dry place with good air circulation for some months. Wrapped in hessian/coir and put in wire hanging planters is ideal.
The large brown tubers are washed, dried in the sun and then stored. The average sugar content of the tubers increases during storage because of starch conversion. Their exposure to the sun, for up to 2 weeks, can accelerate the sweetening process.
The tubers have an appealing crunchy sweet crispness that is a cross between apple and melon. To eat yacon raw first remove the resinous tasting outer brown skin and inner white skin by peeling, to reveal the tubers amber coloured sweet crunchy flesh. They impart a sweet flavour and texture to salads and make an interesting addition to a plate of raw vegetable crudités. Yacon can also be served hot – boiled, steamed or baked and will retain their crispness. The tubers juice well and can be used to sweeten other juice combinations. The juice can then be reduced, by boiling to produce syrup. The young stem can be used as a cooked vegetable.
Quite successful pickles can be made by cutting the tubers into dice-sized chunks and soaking them in brine, adding a bit of whey to get those lactobacilli working. The trick is to keep the chunks weighed down so that anaerobic fermentation occurs. The result is a sweet and sour pickle.
Nutritionally yacon is low in calories but it is said to be high in potassium.
The sugar in the leaves of Yacon (fructooligosaccharides (FOS) is in the form of inulin rather than sucrose, so most of the calories are not metabolized, making this suitable for use as a tea for type 11 diabetics. These oligofructans have been recently classified as “prebiotics.” Since they are not digested in the human gastrointestinal tract they are transported to the colon where they are fermented by a selected species of gut micro-flora (especially Bifidobacterium and Lactobacillus) and help to balance gut flora and aid digestion.
The tubers grow well beneath a canopy of trees and can used as a soil protector because of its ability to maintain itself as a perennial species, especially in dry agro-ecological areas. If used this way don’t expect a yield of tubers but grow instead as animal forage. Yacon leaves have a protein content of 11-17% and when cut the foliage sprouts again from the underground stems. For very best yields of tubers a deep rich well-drained irrigated soil is necessary