About Rhynchosia precatoria (Humb. & Bonpl. ex Willd.) DC.
Rhynchosia precatoria is an herbaceous vine that typically twines, and sometimes sprawls. It can climb to heights of several meters when growing under ideal conditions. Its stems are covered in hairs that range from long and soft to stiff and appressed to the stem surface, and yellow dot-like glands are sometimes mixed in among the hairs. Each petiole grows up to 7 centimeters (2¾ inches) long, and holds a compound leaf made of three hairy leaflets that can reach up to 12.5 centimeters (~5 inches) in length. This species produces raceme inflorescences that grow up to 30 centimeters (~1 foot) long, with individual flowers attached to pedicels that reach up to 2 millimeters (5⁄64 inch) long. The flowers are dark or brownish purple with yellow stripes, and their petals grow up to 9 millimeters (23⁄64 inch) long. Its fruits are legumes that split open to release one or two roundish seeds. The seeds can grow up to 8 millimeters (5⁄16 inch) long, and are red with a black spot. Rhynchosia precatoria ranges from southern Arizona and southern Florida in the United States, south through moister regions of Mexico, and may extend through Central America into Colombia in South America. Taxonomic authorities do not currently agree on how far south the species naturally occurs; as of now, documented observations on the iNaturalist page for this species stop around the Guatemalan border. In the United States, Rhynchosia precatoria grows in open areas, thickets, and forests on sandy or limestone soils, at elevations up to 1200 meters (~3900 feet). In Nicaragua, the species is commonly found in gallery forests and disturbed areas. The photographs accompanying this description come from an individual found at the weedy edge of a forest in very hot, humid conditions at the end of the dry season. This individual grew at around 200 meters (~650 feet) in elevation, on Mexico's southern border with Guatemala. The attractive red and black seeds of Rhynchosia precatoria are most often used for artisanal purposes, such as making bracelets and necklaces. In Mexican traditional medicine, the Mayo people of northwestern Mexico use aqueous infusions of the plant to treat respiratory illness and inflammations. Clinical tests of these infusions have shown they have anti-inflammatory effects.
