Heteropterys glabra is a woody tropical vine favoured for its five-petalled yellow flowers and reddish-pink immature fruits. The first fruits appear shortly after the initial flush of blossoms and ripen on the vine as the plant continues to flower, such that flowers and fruits can be observed together. Resembling the fruits of maples (though in an entirely different plant order, nevermind family or genus), each fruit is a schizocarp consisting of up to three mericarps if pollination and fertilization are completely successful. Each mericarp is a samara containing a single seed. As the fruits mature, the schizocarps become dry and brittle. The samaras are eventually dispersed by wind.
The fruits are the inspiration for the genus name, which is derived from the Greek words heteros, meaning “different” and pteron, meaning “wing”. Heteropterys is the only genus within the Malpighiaceae in which the largest samara of each schizocarp curves upward rather than downward, and has a lower margin that is thicker than the upper margin, instead of the other way around. The fruits have also earned the plant its common name, redwing. Other common names include mariposa and glabrous heteropterys. New leaves of Heteropterys glabra are burgundy-coloured, changing to green at maturity.
Redwing is endemic to Argentina, southern Brazil, Paraguay and Uruguay. In northeastern Argentina and the surrounding areas, redwing is grown for its immature fruits; decoctions of these are traditionally used as sedatives and anxiolytic (anxiety-reducing) agents (Amat and Yajia 1991). In a 2005 study published in the Journal of Ethnopharmacology, Galietta et al. found that an extract made from Heteropterys glabra fruits caused a decrease in spontaneous motor activity in mice and lessened both the electrical activity in the brain and the speed of response to visual stimulation, supporting the extract’s effectiveness as a sedative and anxiolytic agent. Stermitz et al. (Phytochemistry, June 1975) found that the leaves and especially the roots of the redwing vine contain levels of a toxic nitro compound called hiptagin or 1,2,4,6-tetra-3-nitropropanoyl-β-D-glucopyranoside, a compound rarely present among Argentine plants.
This species is cultivated as a specimen plant in North America (USDA hardiness zones 7 and higher), where it flowers throughout the summer. It grows best in a sunny position with moist, well-drained soil. The vine will climb a support if one is provided, or will intertwine with itself to form a mounded shape in the absence of one.