Macroptilium atropurpureum

Native from Texas through Mexico, Central America, the Caribbean, and tropical South America, this perennial herbaceous vine climbs or trails across open habitats. Its stems can extend about sixteen feet, supported by a deep, swollen taproot. Dark reddish-purple, nearly black pea-shaped flowers appear in upright clusters. The plant occurs along roadsides, coastal dunes, mangrove edges, and other disturbed ground, and is commonly called siratro. It has become an environmental weed in Queensland, Australia, where it can spread over and smother surrounding vegetation. Photographed in Colombia.