Cymbopogon citratus, commonly known as lemon grass as well as oil grass, is a tropical plant from Southeast Asia which is often sold in stem form. Its leaves are used to make tea which can relieve stomach and gut problems. It can also act as an antidepressant and as a mood enhancer. While it can be grown in warmer temperate regions (such as UK) it is not hardy to frost. In Brazilian folk medicine it is believed to have anxiolytic, hypnotic and anticonvulsant properties,[2] but at least one study has found no effect in humans.[3]

Taken from the http://en.wikipedia.org/wiki/Cymbopogon_citratus.