Ruellia simplex, the Mexican petunia, Mexican bluebell or Britton's wild petunia, is a species of flowering plant in the family Acanthaceae. It is a native of Mexico, the Caribbean, and South America. It has become a widespread invasive plant in Florida, where it was likely introduced as an ornamental before 1933, as well as in the eastern Mediterranean, South Asia and other parts of the eastern hemisphere.
Ruellia simplex is an evergreen perennial growing 3 ft (0.91 m) tall, forming colonies of stalks with lance-shaped leaves that are 6 to 12 in (15 to 30 cm) and .5 to .75 in (1.3 to 1.9 cm) wide. Trumpet shaped flowers are metallic blue to purple, with five petals, and 3 in (7.6 cm) wide. There is a dwarf variety that is only 1 ft (0.30 m) tall.
Ruellia simplex is native to Mexico, the West Indies, western Bolivia, southwestern Brazil, Paraguay, Uruguay, and northeastern Argentina. It has been widely used as an ornamental plant and has escaped from cultivation in the United States, Australia and parts of Asia, as well as several Pacific Islands. It has become invasive in some of these areas, forming dense, single-species stands of vegetation which threaten native plants. It is mainly a plant of wet places such as ditches, pond verges, lakesides and marshes, but can survive in drier conditions.
