Helicteres is a genus of about 60–70 species of shrubs and small trees in the mallow family Malvaceae (order Malvales). The genus is immediately recognisable by its distinctive fruits: tightly spiralled or screw-shaped follicles that give many species their common name "screw trees." Flowers are typically red, orange-red, or pink, and in Asian species are frequently pollinated by sunbirds, butterflies, and other Hymenoptera.
The genus has a pantropical distribution spanning two widely separated ranges. In Asia it extends from southern China and the Indian subcontinent through Southeast Asia to northern Australia; in the Americas it occurs from Mexico south through the northern half of South America. This disjunct pattern reflects the family's Gondwanan ancestry and subsequent dispersal history across the tropics.
The best-known member is Helicteres isora, the Indian screw tree, a shrub or small tree of dry deciduous forests across South and Southeast Asia. Its twisted, horn-like fruits have long been used in traditional medicine across the region, and its bark yields a tough bast fibre historically employed for rope, sacking, and cordage.
Distribution
Helicteres has a disjunct pantropical range. Asian species extend from southern China and the Indian subcontinent through Southeast Asia and the Malay Peninsula to northern Australia, occurring mainly in dry deciduous forests, scrub, and grasslands at elevations of roughly 100–600 m. American species range from Mexico through to the northern half of South America.
Ecology
Species of Helicteres are characteristic of dry deciduous forests, scrub, and dry grasslands, typically on hill slopes. In South Asia, H. isora is most abundant in central and western India. The red to orange-red flowers of Asian species are pollinated primarily by sunbirds, butterflies, and Hymenoptera.
Cultural Uses
Several species of Helicteres, especially H. isora, have a long history of use in traditional medicine across South and Southeast Asia, as well as in Iraq and South Africa. The fruits and roots are used in folk remedies for gastrointestinal disorders, diabetes, and infections; the root and stem bark are considered expectorant, demulcent, and astringent, and are used to treat diarrhoea, dysentery, and scabies. The tough bast fibre from the bark was historically made into rope, sacking, cots, and cordage for agricultural use.
