Lemon grasses (Cymbopogon spp.) include about 55 species, some of which contain essential oils that give the plants a flavor and scent similar to citrus fruit. Probably the most well-known species is west Indian lemon grass (_Cymbopogon citratus_), which is used in food as well as an ingredient in insect repellents. West Indian lemon grass doesn't repel rodents, but it has several effects on them.
Native to India and parts of Southeast Asia, west Indian lemon grass is a 2- to 4-foot-tall, tropical, ornamental grass that grows as a perennial in U.S. Department of Agriculture plant hardiness zones 10 through 11 or zones 8b through 10, depending on the source. Elsewhere, it is often grown in a pot so that it can be easily used in cooking. Because it can become somewhat invasive, growing it in a pot is an effective way to keep it contained. A container housing the plant should have holes in its base to allow water to drain freely. West Indian lemon grass thrives in full sunlight or partial shade and in any type of soil that is consistently moist but well-drained.
The fragrant essential oil extracted from the leaves of west Indian lemon grass can harm or kill insects, but it does not harm humans. The scent of the grass is usually enough to repel insects. The repellent effects last two to three hours.
The plant's essential oil is also antimicrobial, which means it limits or stops the growth of microorganisms.
Many lemon grass species contain myrcene, which has been found to have an analgesic, or pain-relieving, effect on mice, according to a report by Sigma-Aldrich Co. LLC that summarizes several studies in which mice and rats were given myrcene extracted from lemon grass.
In addition, a study published in Cytobios in 1996 and conducted by the Department of Biological Sciences at the University of Lagos in Nigeria found that mice given a liquid extract of west Indian lemon grass -- obtained by boiling the plant's leaves -- were rid of the malaria parasite, but the rodents died days later.