Know Your Hedge Vetiver: Environmental Concerns About Vetiveria zizanioides

Mark Dafforn, Office of International Affairs, National Academy of Sciences,
Washington, DC 20418, USA

A 1993 National Academy of Sciences' study found vetiver hedges cheap safe and effective in their ability to slow erosion and retain moisture. Any new solution to a global problem seems miraculous, but such a fundamental insight naturally raises many doubts. Most can be and have been answered scientifically. Some, however, are value judgments or are otherwise not amenable to proof The possibilities that vetiver grass (Vetiveria zizanioides) may sometime, somewhere, harbor pests, plagues, or be invasive are especially challenging. The introduction of vetiver on a vast scale therefore evokes a number of ongoing environmental concerns. This paper provides a background for addressing those questions. The status of vetiver as a domesticate is considered, as is the possibility of differentiating hedge-grade" vetivers. Adequate accession records are emphasized, and an opportunity for submitting vetiver samples for DNA analysis is presented. As responsible scientists and practitioners, it is necessary to deal with misgivings in a rational and honest manner. Providing reasonable, factual, and balanced information seems the best strategy for promoting societal acceptance of this natural innovation in landscape stabilization, one which is already changing the face of the tropics.

Thanks to the generous sponsorship of King Bhumibol, we here at the International Conference on Vetiver Grass have seen the scientific proof that vetiver is a miracle grass". But in 1989, when we at the US. National Academy of Sciences first heard of it, vetiver sounded too good to be true. Erosion has been recognized since ancient times as the enduring enemy of human works, and the inevitable power of water against rock is a metaphor in every culture. Agriculture in particular, with soil laid bare to the rains, is a paradox: the very action that feeds us ruins us. We must clear the earth to plant, and the earth is swept away. Our tools against erosion-traditionally earth or stone-are almost all expensive, and almost always temporary.

In 1989, two World Bank veterans of tropical agriculture, John Greenfield and Richard Grimshaw, were claiming to have a simple, natural answer to soil loss and moisture control They based their beliefs on what they had seen in traditional sugarcane agriculture. A contour hedge of grass, dense with stems at ground level, slows water enough that it drops sediments, layering behind itself a self-leveling bench terrace from which water flows gently and smoothly. Between the hedges can run fields, roads, canals, and other features of the "built" and natural environment. They declared that this biological system of erosion control, particularly using a ubiquitous tropical grass called vetiver (Vetiveria zizanioides) could be effective almost anywhere.

The Academy Vetiver Study
My colleague at the Academy, Noel Vietmeyer, with whom I've worked for ten years as a research associate, and I were skeptical to say the least. The purpose of the National Academy of Sciences, founded in 1863, is to "advise on matters of science and technology" through its National Research Council (NRC). Since 1970, our small NRC program has reported on technology innovations with the potential to help developing countries. During this time we have heard of hundreds of "breakthroughs" which might feed the world, or produce abundant fuel, or remedy any of a dozen of humanity's crises. Most solutions are impractical and would cause more problems than they solve. On the other hand, some ideas have true merit, and our program has produced over forty studies highlighting the potential of under exploited crops, fast-growing trees, and little-known animals. almost all the innovations have been based on natural resources already important to some people at some time in some place: "lost" crops, "micro" livestock, "firewood" trees. Our job has been to draw on the best knowledge available to evaluate and explain whether these "new" resources truly had the potential to improve the quality of life and, if so, to make this information widely available with the endorsement of the National Academy of Sciences. In a sense, we put into practice the English saying. "The proof of the pudding is in the eating.": after all is said and done, does something work?

By 1989, John Greenfield and Richard Grimshaw had been very successful promoting vetiver hedges in World Bank projects in several countries. The US. Department of Agriculture (USDA) was exploring the idea of grass hedges for use in the United States, and had even sent an exploratory team to visit vetiver projects in India. The US. Agency for International Development (USAID) saw the potential of the vetiver system in many of its "sustainable agriculture" projects. But prudence dictated that before those agencies promoted the vetiver system, it should be investigated for both its strengths and weaknesses. Given other experiences caution was wise, for there seems to be a "law of unintended consequences" which states that the unexpected outcomes of our actions are often more costly than the anticipated benefits. So the World Bank, USDA, and USAID contracted for the National Academy of Sciences to " ... assess the state of knowledge, the promise, and the possible limitations of vetiver use, as well as research that might be needed before vetiver can be deployed rationally and safely.".

As in all studies, we assembled a panel of supporters and skeptics. It was chaired by Norman Borlaug, whose high-yielding wheats had averted unprecedented starvation in the 1960s, for which he received the Nobel Peace Prize in 1970. The other panelists were Rattan Lal, author of several standard texts on erosion (including Soil erosion in the tropics: principles and management, and Soil erosion research methods); David Pimentel, a developer of integrated pest management and systems agriculture; and Hugh Popenoe, a senior authority on tropical agriculture and land-use systems.

It was David Pimentel who recast our task as "scientifically validating a traditional practice". This was made clear as we learned that vetiver hedges had long been used for erosion control. Vetiver was standard agricultural practice in places such as Fiji, Mauritius, and St. Lucia. We found that much of our background work had been done by farmers and colonial agronomists: vetiver is not only well-known for the essential oil produced from its roots, but vetiver erosion-control hedges had often been recommended in the literature. Our task was not to create new or hypothetical knowledge, but largely to assemble and evaluate the wealth of existing experience and bring it to global awareness. We gathered agricultural and botanical information from around the world, eventually contacting in our quest for positives and negatives over 500 people (plus soliciting experiences from the then-I 000 members of the World Bank's Vetiver Network). After four years, a mass of information was distilled into the peer-reviewed study Vetiver Grass: A Thin Green Line Against Erosion in which the NRC panel unanimously reported that vetiver hedges were a cheap, safe, and effective technique to slow erosion and retain soil moisture. Vetiver could be used with confidence, but much remained to be learned. We should increase our knowledge of the system to the level known about engineered erosion structures, and of vetiver to the level known about other plants such as rice or wheat.

Doubts About Vetiver
This study was unique for Noel and me in that none of our other reports had touched upon the resolution to something as basic and widespread as erosion; it became clear that vetiver truly was an innovation of the first importance. The objections to vetiver were more unimaginative. Skeptics often seem to fall into three categories: traditionalists, innovators, and generalists. In this case, the traditionalists felt that proven technologies were the best immediate answer to the erosion problem: engineered structures were expensive to build and maintain, and it was difficult to get people to construct and maintain them, but they worked and what was needed was more investment and more education. The innovators felt that there were many other ways to combat erosion, using contours and bunds and stone and vegetative debris and dammed ridges and trees and swathes of grass and scores of other techniques which largely depend on local conditions and local initiative and continual upkeep. The generalists themselves often acknowledged that vetiver worked wonderfully, but that the law of unintended consequences precluded its use: there was too little known and there had been too many blunders in the past. It was better where it could be afforded to stick with what was already proven, and elsewhere to suffer unchecked erosion rather than try the unfamiliar. Although vetiver was well-known to many in the tropics, status quo and risk aversion are strong inhibitors of innovation.

The first two types of objections, those from the traditionalists and the innovators, can be
answered objectively. Quantifiable scientific data can show the relative costs and benefits of vetiver hedges. The amazing outburst of research and application catalyzed ten years ago by Grimshaw and Greenfield, and the great advances in knowledge documented by participants at this conference, have clearly demonstrated that vetiver hedges are a fundamental advance over both traditional and innovative erosion control methods. Vegetative grass barriers are an insight which is qualitatively different from most past approaches ... it is what Noel Vietmeyer calls "nudging nature". The vetiver system uses a natural process that grows stronger and more stable with time, rather than weaker and more vulnerable as do most other erosion-control techniques.

The now-obvious insight into the workings of a vetiver hedge has been in front of humans for centuries, in the soil built up along fence lines running across the contour, the silted debrisdams in contour row crops, even in dirt built up behind grass growing in the cracks of sidewalks. We have just been unaware about what was happening in front of our eyes. We lacked the insight. As John Greenfield is fond of saying, 'We looked but did not see!" Today, the basic concept of the vetiver system is itself proven, and now the minutiae of soil, shade, rooting, and many other factors are being documented in ever-greater detail. Propagation, planting, and management techniques are nearly mature. Standards and specifications are evolving, combining engineering and agronomic principals. This blossoming of agro-engineering is exciting. Such results as epitomized by this conference and now a part of the scientific literature were summarized by our panel: Vetiver hedges are cheap and effective. There are circumstances in which other approaches are appropriate, but even then they are usually improved upon by incorporating a hedge as a key component of the system.

But during our study the generalists asked the more difficult question: Is vetiver safe? Unlike the misgivings of traditionalists and innovators, this fundamental question can not be completely answered objectively, for it is part value judgment and part null hypothesis. Just because we know no fatal flaw, we can not prove one does not exist. The question "When do we know enough" is one of the most vexing in science, and is often answered "never". Scientists are famous for always needing more research, more data, before they can give a final answer. But just as the emergency physician rarely has all the information needed to make an absolute diagnosis and so is forced to rely on past experience, scientists are forced to make recommendations based on incomplete knowledge. It is a balance between perceived risks and perceived benefits. For this reason, the techniques of risk-assessment have evolved to evaluate the unknown. The physician often makes quick decisions based on incomplete information because life is immediately at risk; the mathematician often develops elaborate proofs over many years. The considered judgment of the NRC Vetiver Panel that vetiver was "cheap, safe, and effective" fell somewhere in between. The line of reasoning is that erosion is the number-one problem in agriculture and vetiver is a well-known plant occurring throughout the tropics whose wider use shows no cause for immediate alarm ... further research is prudent. Ethically logical but unprovable.

There is no final answer to the question "Is vetiver safe?". It will always be a value judgment based on past experience and new information. The "generalists" have three particular - and very valid questions which will require vigilance as vetiver is planted on a massive scale:

1. Does vetiver harbor some pest or plague - is it a "vector" - which will ravage some crop or the environment?

2. Is vetiver itself vulnerable to some pest or plague which will make it unusable or, worse, cause a collapse of the vetiver system, leaving tracts of land unprotected by any erosion control mechanisms? This is especially worrisome if one vetiver clone is used as a monocrop across vast areas.

3. Is vetiver a weed, a plant which can invade and naturalize on its own?

I will briefly discuss the first two questions together, and deal with a framework for vetiver's weediness in greater detail. But let me point out some basic precepts to he kept in mind. First, ignoring concerns will not make them go away. Every country has plants which have run rampant or become a reservoir of disease or pest. Second, belittling the risks will only antagonize; that's human nature. Third, bombarding people with one-sided information will only confuse and, if just one fact is incorrect, the whole body of knowledge is made suspect. And fourth, steamrollering over people's objections will only strengthen their determination to oppose.

A passing word on "miracle" plants. The word is used among the smug as a snide or pejorative term, but I believe it was chosen for this conference, "Vetiver: A MiracIe Grass", as a challenge. There are those so jaded or cynical that they forget we are surrounded by miracle plants ... those special plants that allow us to live as "domesticated" humans. Rice, wheat, maize, tell me these aren't "miracle grasses"! Bamboo. Beans. Pine. Potato. I'd say there are at least a hundred miracle plants for which we humans should be eternally grateful so vetiver would now make it one hundred and one. Vetiver seems destined to become a "global grass".

Pests and Plagues
The main pest-and-plague problems reported with vetiver have been few: fungal dieback from Helminthosporium and Bipolaris, bacterial leaf blight from Xanthomonas, sooty molds such as Meliola, stem borers and white grubs, maize cyst and root-knot nematodes, termites, and rats. The genus is susceptible to smuts from Tilletiaceae and from Ustilaginaceae. There is even an ascomycotina fungus called Phyllachora vetiveriicola indigenous to Gorakhpur, India, although I know nothing about it except that members of the genus cause leaf-spotting (black spot, tar spot) and they may be genus specific (there are species named P. sorghi, P.sacchari, P. maydis; P. eucalypti, P. ficiuum, etc.).

None of these pathogens have caused a failure of vetiver in the field, nor is there evidence of transfer to other crops. There are no reported cases of vetiver serving as a reservoir for pests or plagues, even when infected plants grow next to hosts. Vetiver has been cultivated on a large scale as an essential-oil plant for centuries, generally in association with our other economic plants. Its vulnerabilities and their treatments are well-covered in the literature. Each of the pests, even the stem borers, is harbored by many other species, so vetiver is not forming a unique refugia. Proper maintenance reduces or eliminates them as problems. Extension officers in Fiji, where there is the longest scientific field experience with vetiver hedges, have pointed out that under a proper maintenance program all known problems can be adequately overcome.

Vetiver seems unlikely to become a devastating vector nor itself catastrophically vulnerable to pests and plagues, no more than other crops planted on a vast scale. Sorghum, maize, and sugarcane are all close relatives which have survived intensive monocropping for centuries. It is of course a constant contest between agriculturists and nature, which thus far we have won with most crops in most places. During an early NRC strategy meeting, I believe Erik Arrhenius of the World Bank pointed out that "without doubt, sometime vetiver will be hit hard by something somewhere. It's only a matter of time". This of course is true, as it is for all our crops. Pandemic disease is a fact of life in modern agriculture. The same will be true for vetiver and somebody had better be ready. Thankfully, agronomy is today a discipline in which both theory and practice excel. That is why vetiver should now be considered as a primary plant resource of humanity, receiving the same intensive research focus and development as our other major crops. I believe that if adequate scientific, economic, and political attention is given to vetiver, we have no more to fear than we do from the many other "miracle" plants which feed, house, and cloth us humans, we who after all are the most evident "monoculture" on the planet.

So vetiver seems a miracle. Will some vetiver become a weed and tarnish that image? I think most definitely not, if vetiver users continue to exercise the judgment and care in the selection of germplasm which they have shown in the past. The vetivers used in hedges do not have rapid reproduction, nor produce vast numbers of indeterminant seeds, nor have creeping rhizomes, nor possess most of the other technical characteristics ascribed to weeds. The two primary "weedy" characteristics shown by good vetivers are their ability to grow in a wide range of habitats and to be unusually persistent where planted. Yet vetiver proves easy to eradicate if desired.

By the way, many people seem to equate "weed" and "exotic", but the correlation is very weak and some of the worst weeds are "home-grown". Almost any weed scientist will tell you that 99% of introduced plants - especially domesticates - will never be weeds (look anywhere at fruits and vegetables, grains, legumes, trees, and ornamentals - most are exotics). Of the remaining 1%, 99% of them can be predicted as weeds; they have that combination of characteristics that cry out "Danger, Warning, Probable Pest". What concerns weed scientists, exotic plant committees, and other professionals is that obscure 1-in-10,000 plant which seems well behaved but which shows unexpected vigor and fecundity in some new environment. Regrettably, much of the clamor against "exotics" comes not from professionals but from armchair generalists. One of our duties is to provide them with field-proven evidence about our well-known vetiver, which has long been grown in every country and clime of the tropics. Nonetheless, it is important to point out our awareness that some members of the species and its congeners certainly do have the potential to be pestiferous, nor do I recall anyone ever denying this possibility.

The genus Vetiveria belongs to the Tribe of grasses called the Andropogoneae [Andropononeae). One of the worst weeds in the world is an andropogon. Imperata cylindrica, widely known as cogon, lalang, and, in Thai, yaa kha, dominates several hundred million hectares of Asia, where it is native. It has little forage value, is persistent, and precludes land from useful purposes. About the only cost-effective way to recover the cogon lands is to battle it with one of those stubborn acacias, Acacia mangium, which has the ability to establish in the tangled mass of grass and eventually eliminate it through its dense shade. Mangium is nitrogen-fixing, fast-growing, and provides an excellent timber. It seems a real innovation in our struggle against cogon, and we hope some day to issue a report on this from the National Academy of Sciences. Incidentally, there is a diminutive form of imperata known in the United States for its red leaves. Called "Japanese Blood Grass", it does not set seed around Washington but scientists in the South, in Mississippi, have shown it seeds abundantly there. Big cogon is already loose in the South, and I have fears about this pretty little ornamental further north.

Also closely related to vetiver is sugarcane. Another member of its genus is Saccharaum spontaneum, infesting nearly every nook and cranny of perennial fields in its Asian home, not to mention roadsides, ditches, and waste areas. It is not as robust as sugarcane, but is much more feisty.

The closest generic relative of vetiver is sorghum (along with Chrysopogon, a widespread brush and lawn grass). Another member of the genus, Sorghum halepense (called Johnson grass in the United States after one of its early promoters), embodies the worst characteristics of a weed. Johnson grass was purposefully introduced in many areas because of its actual value for forage. It proves pioneering, invasive, and persistent; it produces both abundant seed and long, burrowing rhizomes, each of which can produce a new plant; it can be grazed, burned, dug, poisoned, and plowed, yet come back year-after-year to form impenetrable canebrakes; seasoned leaves develop prussic acid, which turns to deadly hydrocyanic acid in animals; and, worst, it has apparently borrowed some genes from its fellow sorghums which allow it to mimic them in seasonality, growth, habit, and reproduction. It continues to evolve, and there seems to be a genetic continuum between Johnson grass and sorghum, including even the sugarcanes which slash yields in almost every field of sorghum in America. Thus, Sorghum halepense has become even more of a pest because of its association with agriculture than it ever was as an unaltered wild plant. Because of this history it is illegal to perform research, at least in parts of the United States, on transgenic sorghum. If one needs examples of undesirable plants, look no further than the andropogons.

If one needs examples of desirable plants, look no further than the andropogons. Most andropogons are perennials, which have a lesser need for seediness; the above examples are exceptions. The entire genus is noted by botanists and physiologists for its tendency towards sterility, surprising, given maize and sorghum. But none of the three most famous and useful andropogons, maize, sorghum, and sugarcane, can reproduce on their own in nature (this is common in domesticates; neither can wheat, rice, cassava, peppers, etc.). The seeds of maize, an unusual plant, are embedded in a cob and encased in a husk through which germinating seed can not penetrate; maize exists solely through human intervention. Grain sorghum has been bred to produce abundant seed, but because the plant throws its weight behind seed production rather than vegetative persistence, the plants themselves can not compete with other plants, especially other grasses. The ditches next to fields of sorghum in Africa, Asia, and America are not filled with sorghum for it can not survive without the disturbance of cultivation. Sugarcane, which like vetiver is not grown for its seed, so rarely flowers that it was only at the end of the last century that seed-producing tricks were discovered that allowed selective breeding to begin. Sugarcane grows where humans plant it; feral plants are vanishingly rare or nonexistent.

Where does vetiver fall between these extremes? Different types seem to approach both ends of the spectrum. Wild forms of Vetiveria zizanioides from Pakistan to the South China Sea produce abundant fertile seed. They are a dominant grass in many areas of the Ganges Valley, and are usually called "North India" vetiver Two points are important to remember about North India vetiver: 1) it is not very useful as an erosion control plant, for it is fairly lank and weak-stemmed, and 2) it is not reported as a weed in places where it has been introduced. Nonetheless, outside its native region, it should not be mentioned in the same breath as hedges.

On the other hand, there are forms of vetiver that for centuries have been selected and cultivated in South Asia and elsewhere for their essential oil. Most rarely flower and many have never been known to set fertile seed. These are usually called "South India" or "nonflowering" types (though they occasionally flower). Like sugarcane, they are extremely well-behaved. Some genotypes have full pollen sterility and/or full embryo abortion. It seems these are the types which were spread throughout the tropics in the last century, both for oil production and because they were used to protect the edges of sugarcane fields from erosion, as we discovered during the course of our study (Vetiver seems to have had two main paths of introduction to new areas. First, it formeded part of "the economic botany kit" of the colonial powers; the finest germplasm was selected for introduction to possessions. Incidentally, much of the vetiver used in hedges came from botanic gardens. The second path was through indentured cane workers, particularly from southern India, who apparently carried vetiver with them to sugar tracts in Mauritius, southern Africa, the Caribbean and elsewhere. A third, undocumented, route was perhaps via the Moors to Iberia and on to the New World. The biogeography of vetiver, reinforced by DNA analysis, will prove a fascinating story when someone takes up the challenge. The old essential-oil types are grown in every tropic soil and clime, and have never been reported to invade or naturalize. They are exceptionally persistent however, sometimes growing in the same row for a hundred years or more. This is why they are legal as boundary markers in parts of Africa and Asia. It is also this quality which helps make them premier hedge plants: they will stay where they are put, but they do not wander.

South India vetiver is also genetically distinct from North India vetiver One study by Steve Kresovich of the US. Department of Agriculture has shown that three essential-oil genotypes from different countries are genetically almost identical, while all three are vastly different from wild North India vetiver. But elaborate tests are unnecessary to tell them apart in the field. They can be visually assigned b~ overall morphology to either the North India or South India "complex" In addition, leaf width and pigmentation, internode length, and several other measurable characteristics set them apart. Further, their oils vary chemically, they rotate polarized light in opposite directions, they smell differently, and are treated separately in commerce. Their taxonomy is tangled.

Incidentally, in the past few decades several countries - particularly India - have had breeding programs to improve the oil content of vetiver root. These efforts have naturally been based on fertile plants. These hybrids look like North India vetivers, but neither these nor the seedy North India types are widespread outside South Asia. It has almost always been the traditional essential-oil vetivers of the Indian Ocean region that show up in other countries. But these days, just because a plant is called an 'essential-oil vetiver" does not mean it is a "non-flowering" vetiver.

Past generations were admirably efficient at introducing high-quality vetiver to new environments, and today it is unlikely that one country has "better" vetiver than another.

Good-quality vetiver is found nearly everywhere, so people do not have to introduce new germplasm. Indeed, it is fortunate vetiver hedges have come into pantropical use without facing the hurdles of phytosanitary quarantine that slows introductions of new plant resources.

So far as I am aware, members of the Vetiver Network have been as well-behaved as their vetivers; people haven't been sticking plants. in their pockets and carrying them to other countries. Now is not the time to start smuggling germplasm! There is no practical need to exchange uncharacterized or uninspected planting material, the risks of introducing new pests or plagues are very high, and that is why unauthorized plant introductions are illegal in most if not all countries. For now, stick with the germplasm you or your neighbors have. Remember that vetiver's global reputation could still pay the consequence for one individual's negligence.

The few international exchanges that have occurred have been among official government programs, and strict quarantine and phytosanitary regulations have been followed. So far as I know, no introductions have entered into hedge use, for the local vetivers have always been as good if not better than the introduced material. If you are looking for vetiver, locate it in your own area or ask your national agricultural service. The Vetiver Network has identified suitable cultivars in almost every country and will be glad to help newcomers find starting material.

It is our duty as vetiver users to ensure we are using good-quality vetiver for hedges. Although seedy vetiver does not make good hedges and vetiver seed has rarely been used, to my knowledge, to establish them, seedy vetivers have been reported in a few countries outside South Asia, such as Colombia and Haiti. (Seed is always so much easier to introduce than vegetative material.) As I said, these are not reported pestiferous. The vetiver species endemic and widely used in Africa, Vetiveria nigritana, is also fertile, as is Vetiveria nemoralis in Southeast Asia. Do not exchange seed outside areas of origin. We must stay on guard that our vetivers are not becoming problems, and we must ensure that new users, as well as skeptics, are aware of the risks and, more importantly, that we know and they know what kind of vetiver we are using.

Knowing Our Vetiver
How can we know our vetivers? There are two complementary paths. The first is to record as much as we can about the history and characteristics of the clones we are using for erosion control. How far back can this plant be traced? Was it used for oil production? Has it flowered? Set seed? Invaded or naturalized? The more we can describe our individual genotypes the better. Name your cultivars and characterize your germplasm, keep records of what you've planted, where, when, in what types of soils and with what kinds of associations, document and publish your experiences, and, especially, report unusual observations to the Vetiver Network.

The second path is to join with others in uniting our knowledge of vetiver This task has been performed honestly and admirably by Richard Grimshaw and the Vetiver Network. Through this same Vetiver Network, I now hope to establish what Noel Vietmeyer calls a "Basic Science Initiative", in this case a Vetiver Identification Program. Using classical and modern techniques of plant morphology and genetics, scientists should be able to unravel the taxonomic, systematic, ecological, molecular, and reproductive biology of vetiver. Because the profile of vetiver is rising in tropical agriculture, several researchers (with access to facilities and funding) have volunteered to assist in understanding the floristic, numerical, and cladistic taxonomy of vetiver, to test and document its ecology and physiology, and to perform DNA fingerprinting using RAPDs, RFLP, and FISH analyses. This is all for the good.

Here at the conference I am handing out accession, descriptor, and DNA forms to help accomplish these goals; these are also available on the internet at, by email at [email protected], and by mail. We hope to soon be able to relate any unknown vetiver to all other vetivers, and to clarify' genetic relationships among wild, cultivated, and hedge vetivers. The next steps will include physically linking genetic sequences with morphological characteristics such as rooting, tillering, flowering, and drought, cold, and chemical tolerances, and perhaps to unravel the many travels of vetiver Perhaps most important, we may discover that some vetivers lack altogether the genetic ability to reproduce.

This is not as unlikely as it seems, and could be accounted for by one of two explanations. The first is that some vetivers may be naturally sterile. Low fertility and low seed-set are considered an evolutionarily advanced characteristic in andropogons, as shown by sugarcane and many of the grasses of my native Kansas prairie. However, if this is the case, there is always the possibility of genetic reversion to more primitive (fertile) states, or that introgression from fertile vetivers or other related grasses would create a reproductively active hybrid, as happens with Johnson grass.

The second explanation is that the essential-oil vetivers are domesticated plants, and having been selected for something other than seed (in this case oil in the roots) they have lost the ability to sexually reproduce, much like potatoes and sugarcane. In preparing this talk, I spoke with Jack Harlan, the USDA plant explorer (he collected vetiver in the 1950s) and geneticist who was elected a Member of the National Academy of Sciences for his contributions to understanding the origins and evolution of cultivated plants. He told me:

The wild vetiver is weedy; it's a seedy plant that has fertile pollen and norma/ meiosis, and it gets around on its own. I think the [traditional] oil-type vetiver is domesticated; it is not fit for surwval in the wild. Because of pollen sterility and irregular meiosis in the South Jndia type, I see no objection to calling it a domesticate. How does this sterile plant get by? Humans have made the sterility persistent by intervention. One could make the claim that is a cultigen. (1/22/96)

If this is the case, and I believe it is, then it is possible that the best oil vetivers are also the most completely infertile: indeed, some essential gene necessary in the reproductive cycle may have been lost forever. A genetically certified sterile vetiver would be the best answer to the weediness question, and such clones may be found to be common through DNA analysis. On the other hand, if domestication is the cause of sterility it is likely that a gradient of fertile-to-sterile vetivers exists, and this too does seem to be true, so we must not forget the example of other domesticated root-crops. Radish and carrot come to mind. A few seedy plants among thousands of sterile plants have allowed persistent and pernicious "allied weeds" to become established and evolve wherever the cultigens are grown. Do not let this happen with vetiver

Remember the King's Rule to destroy any plants with seed (see below). Remember, our ancestors were cautious and only introduced the best. It seems likely - and we will soon know for surethat Jack Harlan is right: most of us are working with domesticated germplasm.

Hedge Vetiver
No matter the origin of the vetivers we use in erosion control, we must always adhere to King Bhumibol's Rules of Vetiver

1. Use only high quality planting material, and destroy any plants with seed
2. Plant vetiver as close together as possible.
3. Maintain your hedges.

Follow the King's Rules: the vetiver system will thrive and skeptics will continue to join us. How can we make it clear to others that we are adhering to the first rule? I recommend we adopt the term "hedge vetiver" for planting material in which we have documented confidence. This phrase would be reserved for plants we would be proud to publically present to national leaders as examples of well-behaved vetiver. It is too early to establish firm practical standards for hedge vetivers, but here are some things to look for: the ideal is robust, dense and erect, with deep roots, wide adaptability, and nonseeding (though perhaps occasionally flowering.

It seems likely that most 'hedge vetivers" will prove to be elite essential-oil types, but that is not clear as yet. Also unclear is whether we are talking about genotypes (vetivers sharing genetic characteristics) or phenotypes (sharing physical characteristics). We know that most vetivers out there are "good", but there are few records of the types of vetiver each of thousands of users are planting. By analyzing the characteristics of many different vetivers, we should be able to establish acceptable standards and unambiguous terminology to clearly and easily identify hedge vetivers. Comments and suggestions are welcome to help establish a grading system to ensure the phrase Hedge Vetiver is synonymous with top-quality planting material. If we promote the use of hedge vetivers, weediness will not be a concern. Establish the concept and practice the use of hedge vetiver

The Hedge Vetiver Challenge
As you can see, I believe the best way to handle skepticism of the vetiver system is to act responsibly and to understand and share the persistent and irresolvable concerns of the "generalists". We must work with them, for they have useful and important perspectives. We as individuals must be especially familiar and confident with the particular cultivar of vetiver were using in our own work ... nothing can be more important both to success in the field and to success in the public's mind. Today, because of workers like you, the vetiver concept is infinitely more secure and robust in the thinking of scientists and bureaucrats than it was ten years ago, but we have only begun to awaken the awareness of the public. And for every inch of vetiver hedge now in existence I envision a mile (I'm sometimes not too metric). Imagine a grass hedge on every two-meter interval in every field in the tropics. This, colleagues, is a major ecological intervention. We must know our vetivers.

At about sunrise the day before the conference, I sat and talked about vetiver with my colleague and friend Jim Smyle of the World Bank's Vetiver Network. We did some quick calculations and conservatively estimated that more than a billion vetiver slips have been planted these past ten years ... it's probably closer to five billion. If vetiver becomes the standard conservation method throughout the tropics, being used in cotton and banana and maize and sorghum and cassava and the other crops, and to protect roads and waterways and civil engineering and watersheds, Jim and I speculated that within our lifetimes vetiver could become one of the most common plants on earth. Perhaps we were carried away by the intensity of this conference, but it demonstrates how serious is the challenge.

We must be prepared to meet that challenge. Although I believe we have the requisite skeleton of information, much remains to flesh out understanding. This exercise could be one of the great untapped adventures for vetiver champions: it gives each of you the golden opportunity to add new wisdom to the world body of scientific knowledge. Many of you are working with this plant every day, and many of you have specialized training to evaluate it. Take up this challenge. There are abundant opportunities for publications and theses on vetiver botany, physiology, pathology, entomology, agronomy, ecology, anthropology ... the list of-ologies goes on. If you tie your findings into these broader disciplines you'll contribute both to the advancement of vetiver and of science. It might even get you a promotion.

Vetiver is becoming a global resource. 'Outside" scientists are increasingly willing to donate their time and resources to work with us and understand this new innovation. Vetiver' 5 rising prominence in erosion control is not the only lure: its central but unresolved taxonomic position in the midst of the andropogons among maize and sugarcane and next to sorghum only reinforces the desire of scientists to unravel its nature. At the same time, more and more people are hearing of vetiver, and that means, always, more and more skeptics. The same objections will be raised again and again, the same poorly informed objections which occurred to Noel Vietmeyer and me back when we first heard of the vetiver system in I 989. We must maintain our patience in honestly explaining the vetiver system, and we must maintain our commitment to improving our knowledge of it.

My commitment, as a scientist working only with paper in Washington, is to initiate the Vetiver Identification Program, and to coordinate accession and genetic records until a qualified team of scientists assumes long-term responsibility. I ask each of you who are using vetiver to document your clones, send copies of your records to the Vetiver Network, and to submit samples for DNA analysis. By participating in this effort you lose nothing while you help us all understand the environmental adaptations of vetiver genotypes, their vulnerability to pests and plagues, their origins, and much more. Hopefully, such results will allow us to quickly understand important agronomic and genetic information about clones, will shorten the time needed to evaluate new vetivers, and prevent much of the germplasm duplication which currently exists.

Using modern analytical DNA techniques, we will also be able to measure the "genetic vulnerability" which exists in hedge vetivers. In any given place most or all vetiver is genetically identical. If a pest or plague can harm one plant, it can harm them all, so it is useful to know how much genetic variety exists, and where. Steve Kresovich has already shown that three 'different" hedge vetivers are genetically almost identical. This is one illustration of what a hundred analyses will uncover. It should be possible to group vetivers into a small number of types whose qualities are well-understood. Such an understanding is essential for efficient research, for confidence in planting hedge-grade materials, for insuring adequate genetic diversity in the future, and for answering questions from those unfamiliar with vetiver

I pointed out earlier that we can never prove vetiver will never be a pest. All is not lost, however; other null hypotheses are that the sun will not rise tomorrow, that we will live forever, and that the government will eliminate taxes. All are possible, but don't count on any of them. Nor do I anticipate that vetiver, properly selected and installed, will ever create an environmental difficulty. I still stand four-square behind the conclusions of our National Academy of Sciences' panel: that vetiver is a cheap, safe, and effective way to slow erosion and increase soil moisture.

The Vetiver Network, lead by Richard Grimshaw, has performed admirably in bringing together and distributing this knowledge. What has been achieved in ten years is epic. The research presented at this conference, sponsored by the King of Thailand and bringing together 200 researchers from more than 40 countries, has provided hard evidence that vetiver hedges are indeed a robust innovation. So is the fact that just last week, after only six years of independent research, technical specifications for grass hedges were published by USDA researchers. It seems likely grass hedges will be approved in the "Farm Bill" currently before the US. Congress as the first legal alternative to engineered terraces for conservation compliance [Ed.-This has since been approved.]. You see, grass hedges are now considered by some authorities to be "accepted practice"; our goal is to make them "standard practice" around the world.

We here today have the good fortune to know vetiver and to know what it can accomplish for agriculture, civil engineering, and the environment. It is our responsibility to spread that knowledge conscientiously, honestly, and thoroughly. I believe we have an historic opportunity to show what a dedicated group can achieve when given the right tool, the right organization, and the right goals. We are building a knowledge base, and in time the concerns will fade. We will stay ahead of the "law of unintended consequences". In the meantime, with Hedge Vetiver, we will change the face of the tropics.

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I would like to thank the following people for advising me in preparation for this talk: Robert Adams, Mary Barkworth, Joy Boyer, Charles Bryson, Mike Dallwitz, Chet Dewald, James Eagan, John Greenfield, Richard Grimshaw, Jack Harlan, Mark Hussey, Hugh Iltis, Elizabeth Kellogg, Doral Kemper, Steve Kresovicll, U.C. Lavania, Gil Lovell, James "Bud" Petit De Mange, Weerachai Nanakorn, Hugh Popenoc, Matiur Rahrman, Rusty Russell, Henry Shands, B.K. Simon, Jim Smyle, Allan Stoner, Tony Tanturn, Je.F. VeIdkamp, John Wiersema, Noel Vietmeyer, and Dale Wol, as well as the scores of scientists I've questioned about this topic over the past seven years. All errors and misstatements are my own. Please contact [email protected] with questions and comments.

The original version of this talk was presented at the International Conference on Vetiver Grass held in Chiang Rai, Thailand, February 4-8,1996.