Yacon
Smallanthus sonchifolius
Yacon (Smallanthus sonchifolius) is a remarkable Andean root crop in the Asteraceae family, producing large, sweet, crunchy tubers that taste like a cross between apple, watermelon, and pear. Unlike most root vegetables, yacon stores carbohydrates primarily as fructooligosaccharides (FOS) — a type of soluble fiber that the human body cannot metabolize, making it an exceptionally low-calorie, diabetic-friendly food.
• One of the "lost crops of the Incas," traditionally grown alongside oca, mashua, and ulluco in Andean farming systems
• The tubers can be eaten raw like fruit, with a refreshing, juiciness unusual for a root vegetable
• Fructooligosaccharides (FOS) constitute 40 to 70% of tuber dry weight, acting as a powerful prebiotic
• Increasingly cultivated worldwide as a functional food and natural sweetener
• The genus name Smallanthus honors the American botanist John Kunkel Small
Taxonomie
• Cultivated since pre-Columbian times, with archaeological evidence suggesting domestication over 1,000 years ago
• Traditionally grown at elevations of 800 to 3,500 meters in the Andean region
• Introduced to New Zealand, Japan, Korea, Brazil, and parts of Europe in the 20th century
• First described scientifically by the Spanish botanists Hipólito Ruiz López and José Antonio Pavón in the late 18th century
• Formerly classified as Polymnia sonchifolia before taxonomic revision to Smallanthus
• Now grown commercially in Japan, Brazil, and New Zealand for its health-promoting properties
Above-ground Growth:
• Erect, robust stems reaching 1 to 2 meters tall
• Large, opposite leaves, broadly ovate to cordate, 20 to 40 cm wide
• Dark green, slightly hairy, with serrated margins
• Plant resembles sunflower seedlings in early growth
Flowers:
• Small yellow composite flower heads, 2 to 3 cm in diameter
• Produced at the top of stems in loose clusters in late summer to autumn
• Not particularly showy compared to ornamental sunflower relatives
Root System:
• Produces two distinct types of underground organs
• Fibrous root system with multiple swollen, fleshy storage tubers
• Tubers are large, irregularly shaped, typically 10 to 20 cm long and 5 to 10 cm in diameter
• Tuber skin is tan to reddish-brown; flesh is creamy white to pale yellow, crisp, and very juicy
• Also produces a crown (caudex) with purple-pink propagative rhizome buds for next year's growth
• Per 100 g fresh tuber: only 50 to 70 kcal — remarkably low for a root crop
• FOS comprise 40 to 70% of dry weight; these are non-digestible sugars that pass through the body without contributing calories
• Excellent prebiotic: FOS promote growth of beneficial bifidobacteria and lactobacilli in the gut
• Very low glycemic index, making it ideal for diabetics and those monitoring blood sugar
• Good source of potassium (approximately 240 mg per 100 g), which supports cardiovascular health
• Contains antioxidant phenolic acids including chlorogenic and caffeic acids
• Provides moderate amounts of vitamin C and several B vitamins
• High water content (approximately 85 to 90% of fresh weight)
• The leaves contain compounds studied for potential blood sugar-regulating effects
Planting:
• Plant rhizome sections (propagative buds from the crown) in spring after frost danger passes
• Space plants 60 to 100 cm apart in rows 80 to 100 cm apart
• Requires loose, well-drained, fertile soil enriched with compost
• Prefers full sun but tolerates partial shade
Growing:
• Vigorous grower reaching 1.5 to 2 meters by autumn
• Requires consistent moisture throughout the growing season
• Hill up soil around the base to encourage tuber development
• Relatively pest-free; may be troubled by slugs or snails on young shoots
• Foliage is killed by frost, signaling harvest time
Harvest:
• Harvest tubers after frost kills the foliage, typically 6 to 7 months after planting
• Dig carefully; each plant can produce 10 to 20 tubers weighing 0.5 to 1.5 kg each
• Total yields of 20 to 40 kg per 10 m² row are achievable
• Tubers sweeten in storage as some complex carbohydrates convert to FOS
• Store at cool temperatures (not refrigeration) for 1 to 2 months
Culinary Uses:
• Eaten raw: peeled and sliced, the tubers are crunchy, sweet, and refreshing — similar to jicama or Asian pear
• Added to salads for a sweet, juicy crunch
• Juiced or blended into smoothies for a naturally sweet, low-calorie beverage
• Boiled, baked, or stir-fried, though cooking diminishes the crispness
• In the Andes, tubers are dehydrated in the sun to produce a sweet, raisin-like snack called "yacon chips"
• In Japan, processed into syrup, tea, and powder as a natural sweetener
• Leaves are dried and brewed into yacon tea, popular in South America and Japan
Other Uses:
• Commercially processed into yacon syrup, a low-glycemic sweetener rich in FOS
• Studied for potential benefits in managing diabetes, obesity, and digestive health
• The plant is also used as livestock fodder in the Andes
• Yacon flour is produced as a gluten-free, prebiotic baking ingredient
Anecdote
Yacon tubers can be harvested weighing up to 1 kg each, and a single plant may produce over 20 tubers — yet despite being packed with sweetness, they contain only a fraction of the calories of a potato because the human body cannot digest the fructooligosaccharides that give them their sweet taste.
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