Macroptilium atropurpureum, commonly referred to as purple bush-bean, or siratro is a perennial legume recognized by its climbing, dense, green vines and deep purple flowers. The plant is indigenous to the tropical and subtropical regions of North, Central, and South America, as far north as Texas in the US and as far south as Peru and Brazil. It has been introduced for use as a food for stock to many tropical regions around the world. It has become an invasive pest plant in a number of areas, including the north-eastern coast of Australia. Rich in protein, M. atropurpureum is commonly used for cattle pastures intercropped with grass, used in hay, or as a ground cover to prevent soil erosion and to improve soil quality.