Mark Dafforn, Office of International Affairs, National Academy of Sciences,
Washington, DC 20418, USA
Abstract
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.
Introduction
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.
Weediness
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.
Germplasm
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 www.vetiver.com, 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.
* * *
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.