Vetiver ( Chrysopogon zizanioides) is a tropical, non-invasive clump forming grass. Vetiver does not have stolons or rhizomes and can only be propagated by division. The roots are fibrous, fast growing and can reach depths of 3-4m after one year in optimal conditions. New shoots grow underground making it resistant to fires, frosts and heavy grazing.
Vetiver is able to:
- Survive in extreme climatic conditions including prolonged drought, flood and temperatures of -15°C to + 55°C
- Tolerate a wide range of soil pH from 3.3 – 12.5 without any amelioration
- Grow in soils with high acidity, salinity and alkalinity
- Tolerate high levels of heavy metals in soils such as – As, Cd, Cr, Pb, Hg, Se and Zn
- Absorb dissolved nutrients such as N & P and heavy metals in polluted water
Vetiver originates in India and is widely cultivated in the tropical, sub-tropical and Mediterranean regions of the world. As a tropical grass Vetiver prefers warm humid conditions with plenty of sunshine. Vetiver does not tolerate shade and grows best in open exposed areas and although dappled shade may be tolerated growth will be reduced. Vetiver prefers sandy loam soils and will tolerate clay loam soils but dislikes heavy clay soils. Vetiver’ ability to tolerate a wide range of difficult soil conditions, generally means that fertilisers are unnecessary, however, trials in Spain (VetiverSpain) have found the addition of ash improves growth rates immensely.
Vetiver cuttings are known as slips and are taken from mature plants and usually have 2-3 stems (known as Tillers). The leaves and roots are trimmed in order to encourage new growth. Vetiver slips can be planted directly into the soil - if well drained - sandy loam is best to get plants established. The temperature needs to be at least 10°C, when the chance of any frost is over. They need to be well watered for the first few weeks until established , this can take 3-4 months. In the northern hemisphere place in a sunny position.
Vetiver slips can be grown in pots for 3-4 months until established – usually 3-4 stems - then planted into wet soil and kept watered for a few weeks. Plants will reach maturity in about one year.
GROWING VETIVER IN THE UK
Although Vetiver is classed as a tropical grass, recent research has demonstrated its ability to withstand colder conditions than previously thought. Vetiver has survived under snow and heavy frosts in field conditions, primarily because the shoots are underground. Although Vetiver won’t survive when the ground is frozen, it has been known to survive to -10°C in Georgia, USA. Vetiver will recover after a period of dormancy and once the upper leaves that will turn purplely brown are trimmed, Vetiver will continue to grow according to the local environmental conditions. Recent research has shown that whilst optimal soil temperature for maximum root growth is 25°C, roots will continue to grow at the rate of 12.6cm/day at 13°C and only go dormant at 5°C, meaning that Vetiver would continue to grow in many UK soils for between 7-8 months of the year.
Vetiver is not suitable for growing throughout the UK, although according to the USDA Plant Hardiness map many parts of the south, southwest and southeast are eminently suitable. Soil type, shade levels and soil temperature are the controlling factors when assessing whether Vetiver will grow sufficiently to provide the relevant application, be it erosion control or slope stabilisation. Using Vetiver for Phyto-remediation will be dependent upon the soil temperature, as when the plant is dormant at temperatures below 5°C then no phyto-remediation will take place. VetiverGrassUK is planning trials to assess the ability of Vetiver for Phyto-remediation in the UK
Due to the shorter growing season in the UK, we suggest that a combination of Vetiver slips and Young Plants are used in order to ensure a successful application. Vetiver should ideally be planted in May-June so the roots have the best soil temperatures to establish themselves before the onset of winter.