Yacon (Smallanthus sonchifolius) is the crisp, juicy, refreshingly sweet storage root of an Andean daisy relative — a tuber with the wet crunch of an apple or water chestnut and a flavour somewhere between pear, watermelon and mild celery. Despite tasting sweet, almost none of its sugar is digestible: it stores carbohydrate mainly as the prebiotic fibre inulin and fructooligosaccharides, so it is very low in usable calories.