Vetiver grass (Vetiveria zizanioides), recently reclassified as Chrysopogon zizanioides, is the main component of many vegetation-based bio-engineering and conservation programmes worldwide. It is affordable and efficient in erosion control and water conservation, soil stabilisation, pollution control, waste water treatment, and storm damage mitigation and prevention.
Originating in India and cultivated widely around the world, it was first used in South Africa by the voortrekkers to scent kists, and grown in Ventersdorp in 1892. It is suitable for the tropics and subtropics, as well as anywhere with hot summers and winters without permanently frozen soil. Most commercial genotypes are sterile. As they propagate by small offsets instead of underground stolons, they are non-invasive and easily controlled by cultivating the soil at the boundary of the hedge.
However, the fertile genotype Chrysopogon nigritana, indigenous to Africa, can become invasive. It is found in Ngamiland, Botswana, the Grootfontein district of Namibia, and central and west Africa.
Characteristics and advantages
It is an ecological climax species that can survive for decades without any aggressiveness or tendency to colonise new areas. Vigorous, with a high biomass production potential in terms of roots and above-ground material. Strong roots that grow to a depth of 4m. As it propagates only vegetatively, its invasive potential is extremely low. Able to withstand both drought and flooding, and tolerant of high levels of pesticides, herbicides and a wide range of toxic and heavy metals.
Can survive temperatures from -14°C to 55°C and soil pH ranging from 3,0 to 10,5. High tolerance to saline soil, sodic soil and acid sulphate soil. Valuable in erosion prevention and control, engineers likening the roots to “living soil nails”. With an average tensile strength of 75MPa, the roots improve the shear strength of soil by between 30% and 40%. With neither stolons nor rhizomes, extremely drought- and frost-tolerant, and difficult to dislodge by strongly flowing water.
Strong and erect stems that withstand relatively deep-flowing water.New shoots developing from the underground crown afford a resistance to fire, frost, traffic and heavy grazing pressure. When plants are established close together, it forms a dense hedge that acts as an effective sediment filter and water flow diffuser. New roots grow from nodes buried by trapped sediment. Vetiver will continue to grow up with the deposited silt, eventually forming terraces if the trapped sediment is not removed.
The plant is palatable in the early stages of growth and reduces stomach parasites in livestock. Vetiver has the potential of becoming an important biological factor in integrated pest management in crop production. Implementing its Vetiver Grass Hedge Row (VGHR) and Vetiver System (VS) concepts, the Gauteng-based company Hydromulch has been using vetiver for decades in its erosion prevention and control projects throughout Africa, the Indian Ocean islands and the Caribbean.
Depending on the quantity, prices for plants (three months old) range from R4,15 to R7,50 each and for slips from R2,35 to R3,75 each ex VAT and delivery. For more information, visit www.hydromulch.co.za.
Products and prices were checked at time of publication. For more information on these products, contact 011 889 0836