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.
They are herbaceous annuals, growing to 15 – 60 cm tall, with bluish green, slightly succulent leaves and large funnel-shaped flowers growing on long straight stems: sometimes erect single stems, other times growing on branching stems that can rise to be three feet tall. Source