[1] 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.

[5] 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.

[6] The University of Florida's Institute of Food and Agricultural Sciences is trying to reduce the number of home gardeners who plant R. simplex by recommending alternatives, especially Silphium asteriscus, Sisyrinchium angustifolium, Stachytarpheta jamaicensis, Stokesia laevis, but also including some R. simplex cultivars that are sterile.