Smallanthus is a genus of perennial flowering herbs in the tribe Millerieae, family Asteraceae (the daisy family), order Asterales. The genus is native to the Andes of South America, with its centre of diversity in the montane and submontane zone stretching from Colombia south to northern Argentina.
Plants in the genus are robust, erect herbs, typically reaching 1–2.5 metres in height. Stems are cylindrical to angular and become hollow at maturity. Leaves are opposite and deltoid, with hairy upper surfaces. Flower heads are composite pseudanthia (as is characteristic of Asteraceae): the outer ray florets are female and yellow to orange, while the inner disc florets are male and yellow-brown. Underground, plants develop both branching rhizomes and swollen tuberous storage roots.
The most prominent member of the genus is Smallanthus sonchifolius, known as yacon or Peruvian ground apple, a species long cultivated in the Andes for its large, sweet, crisp tubers. Yacon tubers are rich in fructooligosaccharides (primarily inulin), which give them a low glycaemic index and have attracted research interest for antidiabetic applications. Other members of the genus include S. maculatus, S. connatus, S. pyramidalis, and S. uvedalia (bear's foot), a North American species found in the eastern United States.
Smallanthus was formerly included in the genus Polymnia before being separated by H. Robinson in 1978. The genus contains approximately 21 species.
Etymology
The genus name Smallanthus was coined by Harold E. Robinson in 1978 to honour John Kunkel Small (1869–1938), an American botanist and specialist in the flora of the southeastern United States. The epithet combines Small (the surname) with the Greek anthos (flower).
Distribution
Smallanthus is native to the Andes of South America, distributed from Colombia and Venezuela south through Ecuador, Peru, and Bolivia to northern Argentina, primarily at mid to high elevations on the eastern Andean slopes bordering the Amazon basin. S. uvedalia (bear's foot) extends the range into the eastern United States. Through cultivation, S. sonchifolius (yacon) has been established in Japan, South Korea, China, the Philippines, New Zealand, and parts of Australia since the 1980s.
Ecology
Members of Smallanthus grow in montane habitats, typically in disturbed edges, field borders, and forest margins at mid-elevations. S. sonchifolius is notable among Andean root crops for lacking photoperiod sensitivity, enabling it to produce commercial yields in subtropical climates beyond its native montane range. Aerial parts are frost-tender, dying back at freezing temperatures, but rhizomes survive underground and resprout. Optimal growth occurs at 18–25°C with adequate moisture and fertility.
Cultivation
Yacon (S. sonchifolius) is propagated from rhizome offsets or stem cuttings rather than from the storage tubers themselves. Plants are vigorous growers — comparable in habit to Jerusalem artichoke — and perform well in loose, fertile, well-drained soil with regular fertilisation. In temperate gardens, planting occurs in early spring after the last expected frost; the tops die back after the first hard freezes in autumn, signalling harvest time. Rhizomes may be overwintered in situ in mild climates or stored cool and frost-free until spring. Tubers improve in sweetness after harvest exposure to sun and cool temperatures.
Cultural Uses
Yacon tubers have been a traditional Andean food for centuries, eaten fresh, boiled, dried, or processed into syrups, jams, juices, and flour. Archaeological evidence suggests the plant held ceremonial significance among the Moche civilisation, with possible depictions on Moche ceramics. In Andean folk medicine Smallanthus sonchifolius is used against liver, kidney, and digestive ailments; in Bolivia specifically it is used against diabetes. Scientific interest has grown since the early 2000s due to its high fructooligosaccharide (FOS/inulin) content, which produces prebiotic, low-glycaemic, and potentially antihyperglycaemic effects in clinical studies. The plant was introduced to Japan in the 1980s, where it became commercially important, and cultivation has since spread across East and Southeast Asia.
History
Smallanthus was long classified within the broad genus Polymnia until Harold E. Robinson segregated it as a distinct genus in 1978. Yacon (S. sonchifolius) remained largely unknown outside its traditional Andean cultivation zone until the early 2000s, when Japanese research and media coverage of its antihyperglycaemic properties triggered rapid commercialisation first in Peru and subsequently worldwide. Today yacon is cultivated across Asia, Australasia, and parts of Europe as a specialty health-food crop, though it remains underutilised relative to its agronomic potential.
