The Vetiver Grass Technology (VGT) is perhaps the world’s most versatile nature-based technology applied to enhance soil and water, and the mitigation of related problems The prime component of VGT is Vetiver grass.
Vetiver is a tropical grass belonging to the genus Chrysopogon (30 identified species). There are two species, both referred to as Vetiver that are of importance to VGT: Chrysopogon zizanioides (L,) Roberty, formerly classified as Vetiveria zizanioides (L) Nash with its center of origin in south Asia; and : Chrysopogon nigritanus (L,) Roberty, classified as Vetiveria nigritana (L) Nash, known as black Vetiver, with its origin in Africa. The two species are rather similar. VGT, and the 40 years of research that supports it, uses primarily Chrysopogon zizanioides, with a strong preference for the domesticated sterile cultivars, originating from south India, that have migrated to most tropical and semi-arid countries.
Vetiver Grass : A botanical description
Chrysopogon zizanioides (L) Roberty, is robust and complex with capability of multiple different applications relating to soil and water. Vetiver grass is a densely tufted, awnless, wiry, glabrous perennial grass that is a “shy breeder”outside of its natural habitats (e.g., swamplands) in South Asia, and genetic testing has shown that it is the domesticated, sterile cultivars of the plant that are today found throughout tropical, sub-tropical, and Mediterranean countries and regions.
It has no rhizomes or stolons and is propagated by root divisions. The plant grows in large clumps from a much branched “spongy” root stock with erect culms 0.5-1.5 meters high The leaf blades are relatively stiff, long, and narrow—up to 75 centimeters long and no more than 8 millimeters wide—and although glabrous are “downward rough” along the edges. The lower glume is muriculated. The panicle is 15-40 centimeters long; joints and pedicels, glabrous. Spikelets are narrow, acute, appressed, and awnless). One spikelet is sessile, hermaphrodite, and somewhat flattened laterally with short sharp spines. It has a glabrous callus, three stamens, and two plumose stigmas. The other spikelet is pedicelled and staminate. Some cultivated forms rarely flower. Chromosomes: Chromosome base number x = 5 or 10. The plant is typically diploid (2n=20).
Both a xerophyte and a hydrophyte C.zizanioides can withstand extreme drought- C.zizanioides achieves drought tolerance primarily through deep root development, osmotic adjustment (notably proline accumulation), and increased antioxidant/secondary metabolite production. These mechanisms collectively enable vetiver to maintain water uptake, protect cellular integrity, and survive prolonged dry periods. The plant is also able to survive l as well as long periods of inundation (up to 90 days has been established in the field and under experimental conditions). It has an exceptionally wide pH range, seems to be able to grow in any type of soil regardless of fertility, and has been found to be unaffected by temperatures as low as -15°C for short periods; freezing soil temperatures will result in plant death The domesticated cultivars (mostly non- or low-seeding South-Indian domesticated types (sterile diploids) of C.zizanioides do not produce seeds that germinate under normal field conditions. C.nigritanus (the African species) and some non-domesticated C.zizanioides accessions from north India do seed, but the seeds being large tend to remain in the vicinity of the mother plant.
Sterility/Invasiveness.
The sterile cultivars C.zizanioides that accounts for almost all germplasm utilized outside of South Asia have proven to be non-invasive. DNA analysis by Robert Adams show that C.zizanioides grown in most countries is sterile and that the sterile cultivars such as Sunshine, Monto and Natal are not invasive as confirmed by the minus 8 rating awarded by the Pacific Island Ecosystem at Risk (PIER).
Non-sterile vetivers tend to be found mainly in their natural habitats – floodplains, swamps, and riverbanks. Outside of these “wet” habitats, because of poor seed dispersal and non-stoloniferous roots systems, fertile vetivers do not appear to be invasive and in any case when used are generally propagated by plant division.
Probably, because of domestication and clonal selection, the sterile non-invasive vetiver cultivars have been found to be superior (greater root mass and depth, denser leaves and culms) to the fertile accessions and are recommended by TVNI as the plant of choice for VGT applications. In countries where the fertile accessions of C. zizanioides and C.nigritanus are native such accessions can be used – it is however recommended to introduce the sterile C. zizanioides where possible as the preferred VGT plant. It should be noted that the majority of vetiver research relating to environmental applications has been undertaken using sterile C.zizanioides
A useful plant guide reference by USDA/NRCS: “Plant Guide ‘SUNSHINE’ VETIVERGRASS Chrysopogon zizanioides (L.)Roberty”
Distinguishing Features
Summary of Characteristics
| Feature | Biological Detail | Ecological /Engineering Benefit |
|---|---|---|
| Hydrology | It can survive complete submergence in water for at least 3 months. | Flood Resistance: Remains intact and functional during severe, prolonged flooding events. |
| Propagation | Cultivars recommended and generally used for VGT are essentially sterile and do not produce fertile seed. | Non-Invasive: It does not spread naturally and will not become a weed or invade natural ecosystems. Propagation must be done vegetatively (by plant division). |
| Tolerance | Will tolerate soil pH from 3 to 11, and temperatures from -15 to +55 degrees C. (it does not survive permafrost). It is extremely drought proof. | Reliability: This large tolerance range ensures the system remains effective across a wide range of climate and soil condition. |
| Toxicity | It is saline tolerant, tolerant to most heavy metals, and to all common herbicides except for glyphosate. | Phytoremediation: Makes it uniquely suited for cleaning up polluted environments, such as abandoned mine sites, agricultural, industrial, and domestic effluents, and contaminated landfills. |
Vetiver Grass Technology applications are generally (not always) designed and applied as a planted, dense vetiver grass hedgerow that has two important features – an above ground filter barrier and a robust below ground root mass that anchors and “drives” the technology and its many attributes and applications.
The Roots:
Vetiver roots are unique and complex, having cells that can modify to adapt to either waterlogged or dry conditions. They also have a special relationship with soil microbes and the exchange of soil nutrients. Paul Truong’s book “The Hidden Half” details these special characteristics and more, and demonstrates how the roots influence the success of various vetiver applications.
The root structure is critical for bio-engineering providing significant shear strength improvement to soil; the roots also interact with soil micro-organisms resulting in soil health improvement, nutrient recycling, improved water infiltration and more.
- “Vertical” roots tend to grow almost straight down with less aggressive lateral roots (neither stolons nor rhizomes) — a crucial biological trait that helps confine the roots within a zone close to the point of planting.
- Deep Anchoring: Vetiver’s root system is extensive, dense, and deep. The roots can grow up to 6 meters in depth.
- Structural Strength: When planted in a dense hedgerow, these roots create an under-ground curtain. The roots that comprise this living wall have remarkable tensile (average 75 Mpa) strength comparable to 1/6 of mild steel, increasing soil shear strength by up to 45%.
- Stopping Soil Loss: This deep vertical architecture can reduce the deep mass loss of soil associated with some landslips.
The Stems and Shoots
The part of the plant visible above ground works in perfect synergy with the root system
to control water flow and soil loss.
- Dense Hedgerow: When planted close together, the plant forms a dense, narrow hedge. The stiff, upright stems and leaves form a thick, fibrous barrier that slows down surface water runoff spreading it more evenly along the hedgerow and preventing the formation of rills and gullies and reducing surface erosion.
- Water Conservation: By slowing runoff, the hedgerow enables the deposition of the sediment load and improves water infiltration some of which replenishes the ground water table.
- Sediment Trapping: The hedge acts as a sieve, trapping eroded topsoil, organic matter, and nutrients behind the barrier. Over time, this trapped material forms natural terraces, further increasing stability and soil depth.
- Biomass Utilization: The pruned leaves and stems are valuable resources. They can be used for excellent mulch, animal fodder, roofing, compost, and for weaving handicrafts (mats, baskets).
- Biodiversity: The above ground biomass makes an excellent habitat for small fauna and insects (the latter are often beneficial). The complex chemical structure (150 identified chemicals) can influence some of these insects and have importance for biological pest control and medicinal use.
A special note on Chrysopogon nigritanus (Black Vetiver).
A growing interest in VGT in sub-Sahara Africa makes it more likely that C.nigritanus will be used for VGT applications under the umbrella of the Vetiver System (VS). Black vetiver has its origin in the Zambezi and Niger Basins and can be found in most of the associated tributaries, flood plains and swamps of the Niger and Zambezi Rivers. It is already used in Malawi, Nigeria, Niger, Senegal and Mali for various uses including soil and water conservation. A 2014 Master thesis “Genetic diversity of Vetiver clones (Chrysopogon zizanioides and Chrysopogon nigritana) available in South Africa based on sequencing analyses and anatomical structure” by Diedericks showed the two species to be indistinguishable based upon the specific and limited set of markers that the study used. The paper notes that Veldkamp (1999) treats them as separate species; but found them to be morphologically very similar. There is, however, the important practical distinction that C. nigritanus seeds freely, which is why it should only be used where it is endemic
Because so little C. nigritanus research has been undertaken, listed below are specific documents that sheds more light on its characteristics and history.
Applications Of Vetiver In Western Africa
Comparison of rooting characteristics of Vetiveria nigratana and Vetiveria zizanioides
Comparisons between Vetiveria zizanioides and Vetiveria nigritana
Vetiveria Nigritana And Its Use In Senegal
Vetiveria nigritana in Senegal — Some notes by Criss Juliard
Potential of an African Vetiver Grass in Managing Wastewater
Get Started
The simplicity of the Vetiver Grass Technology means anyone can learn to use it.
Ready to explore how you can put the Vetiver grass to work in your community or project? Explore more in our website.