Vetiver (Chrysopogon zizanioides) is a perennial grass of the Poaceae family, native to India. The name comes from Tamil. In western and northern India, it is popularly known as khus (please check Opium_poppy#Use_as_food), giving the earlier English names cuscus, cuss cuss, kuss-kuss grass, etc. Vetiver can grow up to 1.5 meters high and form clumps as wide. The stems are tall and the leaves are long, thin, and rather rigid; the flowers are brownish purple. Unlike most grasses, which form horizontally spreading mat-like root systems, vetiver's roots grow downward, 2–4 meters in depth. Vetiver is closely related to other fragrant grasses such as Lemon Grass (Cymbopogon citratus), citronella (Cymbopogon nardus, C. winterianus), and Palmarosa (Cymbopogon martinii). Though it originates in India, vetiver is widely cultivated in the tropical regions of the world. The world's major producers include Haiti, India, Java, and Réunion.
Several aspects of vetiver make it an excellent erosion control plant in warmer climates. Unlike most grasses, vetiver does not form a horizontal mat of roots; rather, the roots grow almost exclusively downward, 2–4 meters. This makes vetiver an excellent stabilizing hedge for stream banks, terraces, and rice paddies. The close growing culms also help to block the runoff of surface water. Because vetiver propagates itself by small offsets instead of underground stolons, it is noninvasive and can easily be controlled by cultivation of the soil at the boundary of the hedge.
In perfumery, the older French spelling, vetyver, is often used.
Vetiver has been used in traditional medicine in South Asia, Southeast Asia, and West Africa.
Old Tamil literature mentions the use of vetiver for medical purposes.
The oil is amber brown and rather thick. The odor of vetiver oil is described as deep, sweet, woody, smoky, earthy, amber, balsam. The best quality oil is obtained from roots that are 18 to 24 months old. The roots are dug up and cleaned then dried. Before the distillation, the roots are chopped and soaked in water. The distillation process can take up to 18 to 24 hours. After the distillate separates into the essential oil and hydrosol, the oil is skimmed off and allowed to age for a few months to allow some undesirable notes which form during the distillation to dissipate. Like patchouli and sandalwood essential oils, the odor of vetiver develops and improves with aging. The characteristics of the oil can vary significantly depending on where the grass is grown and the climate and soil conditions. The oil distilled in Haiti and Réunion has a more floral quality to it and is considered of higher quality than the oil from Java which has a smokier scent. In the north of India, an oil is distilled from wild-growing vetiver. This oil is known as Khus or Khas and is considered superior to the oil obtained from the cultivated variety. It is rarely found outside of India as most of it is consumed within the country.