Scientific Name: Catharanthus roseus
Tamil Name: Nithyakalyani
Description: Large herb upto 75 cm tall. Leaves simple. Rounded with whitish vines. Flowers are showy with a rosy pink. Pods are slender.
Note: In the wild, it is an endangered plant; the main cause of decline is habitat destruction by slash and burn agriculture. It is also however widely cultivated and is naturalized in subtropical and tropical areas of the world.
Photo source: http://en.wikipedia.org/wiki/Catharanthus