Citronella grass, a southeast Asia native, grows in clumps that can reach 6 feet tall and 6 feet wide. Citronella grass has canes topped by long, coarse leaves. It is a perennial in U.S. Department of Agriculture plant hardiness zones 10 through 12. In other areas, it is grown as an annual because it dies back during winter. Citronella grass grows best in full sun and is propagated by clump division. This tropical plant contains citronella and gives off a citronella fragrance. Citronella grass is the source of commercially extracted citronella oil.