Eustoma

Eustoma grandiflorum

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. The flowers can grow up to two inches across and can be found in a variety of colors. They have been found in all shades of pink, purple, white, and blue. In addition, some are bicolored and some are occasionally found in yellow or carmine-red.
Lisianthus flowers are either single flowered or double flowered. Both types of floweres can be found in all rages of the possible colors listed above.
They are usually one to three feet tall. Although there are dwarf varieties the only grow up to eight inches in height. Lisianthus flowers are tricky to grow and require some maintenance. They have tiny seeds that must be sown on the surface not buried and they must be planted in rich well drained soil as well as exposed to full sun. Make sure to keep them moist but do not over water, over watering may result in the growth and development of fungal diseases. Lisisanthus flowers will begin to bloom in early summer and some will continue to bloom throughout the later months of the summer. When cut, Lisianthus flowers can last anywhere from two to three weeks in a vase, they are a very elegant flower that look nice on display.
Eustoma russellianum is particularly popular and has a number of cultivars that are grown for the cut-flower market. The cultivated flower is also often known as Lisianthus, Texas Bluebell, Prairie Gentian (ITIS), Tulip Gentian or just Gentian, although the last name can cause confusion with the related Gentian plant genus. Eustoma is named after the Greek words eu, which means beautiful, and the word stoma which means mouth. Lisianthus on the other hand comes from the Greek word lysis, meaning dissolution as well as the word anthos, which means flower.

Source:  http://en.wikipedia.org/wiki/Lisianthus