Eustoma, a genus of three species in the family Gentianaceae, grows natively in warm regions of the Southern United States, Mexico, Caribbean and northern South America. Examples grow mostly in grassland and in areas of disturbed ground. These flowers are commonly known as Lisianthus flowers.
Lisianthus flowers are either single-flowered or double-flowered. Both types of flowers can be found in all ranges of the possible colors listed above. Source