For the older generations living in the hillier parts of the Caribbean, it used to be widespread knowledge that there was a grass that could be planted to help keep the hillside soil from slipping down with heavy rainfall. Over generations, this oral knowledge became less and less widespread — but as the Caribbean faces ever-growing impacts of climate change, there has been a resurgence of interest for utilising this plant and other plant-based methods to help solve the problems we face in the region.
But vetiver grass — or Chrysopogon zizanioides — is not a one-trick pony. In UWI St Augustine’s Faculty of Food and Agriculture, deputy deans Dr Gaius Eudoxie and Dr Ronald Roopnarine, and lecturer Dr Kegan Farrick have been working with students, alongside local NGO IAMovement and its sister company VetiverTT, for the past six years to uncover more about the capabilities of this multipurpose plant, and how we can utilise it for nature-based solutions to human problems.
“What we really wanted to understand and to do some local investigations on is the ability of this particular grass species to serve multiple soil-related functions within our agricultural and ecological setting,” says Dr Eudoxie.
Of course, its impact on soil is not the only useful trait of vetiver grass. It is well-known for the distinctive fragrance of its roots, used to produce oils for perfumes and cosmetics, and its sturdy, thin leaves can be dried and woven into craft items like mats or baskets.
For the past 50 years, it has been known to be found in the region, although the plant is endemic to India. The word vetiver itself has a Tamil origin, from the word “vettiveru” which means “root that is dug up”. In some parts of Trinidad, like hilly Paramin, the older residents know it as “metiver”. Across the islands, it has morphed into “vectiver” in Dominica and “voltiver” in Saint Lucia.
But whatever it is called, the root remains the star of the show, and the part of the plant that Dr Eudoxie’s research team honed in on for their research. The fibrous roots can grow down to 3m (10ft) deep within two years of planting, and have an average root strength of about one third the tensile strength of steel.
“We started off with four key areas of research focus,” he says.
The first was rehabilitation of degraded soils that had been damaged by human intervention. “We started working in the quarries, and looking at vetiver’s ability to stabilise disturbed soil and serve as a succession species to allow for rehabilitation of the soil in line with more permanent vegetation in line with some of our primary forestry.”
IAMovement has been collaborating with the National Quarries Company Limited since 2018, with the Integrating Water, Land and Ecosystems Management in Caribbean Small Island Developing States (IWEco) Project facilitated by the EMA. The goal of this project is promoting biodiversity and ecologically thriving landscapes. Vetiver is on the front lines of this mission.
Civil Engineer Jonathan Barcant, founder of IAMovement, says that, “We have also deployed over 20,000 vetiver plants at the quarry sites to reduce erosion, build back topsoil, and lock carbon and organic matter deep in the ground through the roots.”
The first step to reforesting an area like a quarry is rehabilitating the soil so that it can be suitable for plant biodiversity. With plants like vetiver that help trap moisture from rainfall deeper into the soil, the site has the chance to get to the level of fertility required to begin planting the secondary vegetation of indigenous and otherwise valuable trees that can form a new, biodiverse forest.
The second project that The UWI team looked into was utilising the plant as a hydrological moderator that regulates the flow of water through the earth.
“We were concerned about its ability because of its deep rooting system to absorb and distribute water across a profile,” says Dr Eudoxie. “[Vetiver is being researched as a way] to moderate water, minimise runoff, and encourage infiltration of the water into the soil.”
When grown in a clustered formation, the vetiver roots intertwine into a tight mesh that slows down the water from rainfall and helps it to seep into the depths of the soil rather than remaining on the surface. With erosion and flooding being a widespread issue in hilly areas, this is particularly valuable as a cheaper and organic alternative to solutions like concrete retaining walls. In agricultural land, where plants tend to have shallower root systems than old forested areas, the soil can be more easily dislodged and brought down by heavy showers which then creates flooding.
This research was also closely connected to their third area of study, looking at the value of the plant for slope stabilisation. In the wet season, landslides have become increasingly common in hilly areas, causing farmers who grow their crops in these areas to suffer losses as the land pulls their crops down with it.
In June 2024, the research team, including Dr Eudoxie, Dr Roopnarine, Mr Akil Crichlow and Mr Federick Pinongcos, published a paper titled “Nature-based solutions for regulating moisture content in an expansive clay soil”, where they examined the impact of vetiver, as well as methods like coconut matting, on regulating the moisture content in soil where high moisture content was shown to be a “triggering factor for mass movement events”. Their research found that vetiver grass treatment had the lowest soil moisture levels of all the methods used.
“The last area that we focused on, is the ability of this grass to be a phytoaccumulator, particularly for heavy metals,” says Dr Eudoxie. “We investigated the potential to remediate landfill leachate.”
He is referring to the process of “phytoaccumulation” (phyto meaning related to plants) through which certain plants can absorb contaminants from the soil and store them within their leaves, stems, and roots. In landfills, where hazardous waste can leach into the soil, grasses like vetiver can be used to help rehabilitate the soil and store these contaminants in a way that can make them easier to remove by harvesting the plants.
Within the region, says Dr Eudoxie, we have not historically utilised vetiver in its function as a phytoaccumulator. While it is known to help protect slopes from slippage, it is fairly recent for any studies to be done on its ability to mitigate the leaching of harmful materials from landfills and similar spaces.
Within the region, says Dr Eudoxie, we have not historically utilised vetiver in its function as a phytoaccumulator. While it is known to help protect slopes from slippage, it is fairly recent for any studies to be done on its ability to mitigate the leaching of harmful materials from landfills and similar spaces.
“This is perhaps one of the first studies in the English-Speaking Caribbean looking at phytoaccumulation from the perspective of pollutant management,” he says.
In one greenhouse study, they exposed the vetiver to various concentrations of cadmium (a toxic heavy metal). “The vetiver was able to accumulate and remove out of the solution significant amounts of cadmium… and we now know that the vast majority of the heavy metals remain locked in the vetiver roots.”
This was important because vetiver is often trimmed using a “chop-and-drop” method, where its leaves are cut and left to nourish the soil around them. If the cadmium was remaining in the leaf, they would simply be returning it to the soil when the plant is trimmed.
“If we are using it for the purpose of phytoremediation, we have to extract the entire plant, ash the plant, and deal with the ash itself,” says Dr Eudoxie.
While the team studying this multipurpose plant have made incredible discoveries over the course of their work, there still remains more to be learned about just how useful it can be to us.
“We recognise that there still remain some challenges in understanding behaviour and use of the plant,” says Dr Eudoxie.
But they are excited to continue their work. After all, their original plan was to spend three years working alongside the IAMovement team, but there has been so much to learn that the team has continued beyond what they could have expected. As we look for ways to use the organic tools around us, this research could mean a world of difference for the Caribbean farmlands and forests of tomorrow.
For more information on vetiver and other initiatives for social and environmental change, visit the IAMovement at https://iamovement.org/.
