Yacon is a South American root vegetable related to North American Jerusalem Artichokes and to sunflowers. The plant can be propagated from pieces of the root. It does not tolerate frost well.
The plant takes about 6 to 7 months to grow. Above ground, the plant can grow up to 7 feet (2 metres) tall. The leaves look a bit like celery leaves, except they are hairy. After it has flowered and the tops start to die back, the tubers are harvested carefully, because they are brittle and will break easily.
The skin of the root vegetable is tan or a purply-brown. Inside, the flesh can be white, yellow, orange or purple, depending on the variety. The size of a Yacon ranges anywhere from 1/2 a pound to a pound (250 to 500g.)
Some varieties are very sweet, others will just be bland. There is no uniformity yet, but breeders are working on it.
Though the edible root is often referred to as a "tuber" for convenience's sake, the edible Yacon root is actually both root and underground stem.
The roots are usually eaten fresh, though they can also be boiled. Fresh, they are sweet, juicy and crunchy -- some people think the taste reminds them of watermelon, others think of chicory roots. When fresh, they can be used raw in salads. Sometimes the roots are allowed to dry in the sun for a bit to make them sweeter. When using raw, peel them first because the skin tastes resiny. When boiling, don't peel first: the skin will come off far easier after cooking. The leaves above ground are cooked like spinach or chard.
The leaves from above ground are actually more nutritious than the root, which is very poor in nutrients. Instead of storing its energy as starch, as do other root vegetables, Yacons store it as inulin (sic), which is made up partly of fructose, a sugar. Humans can't digest inulin, so our bodies don't use it, reducing the number of calories and the food value in subsistence cultures from eating Yacons.
The Incas cultivated it.