22 February, 2024


On The “Virtuous Weeds”: What Weeds Taught Me

By Nimal Chandrasena

Dr. Nimal Chandrasena

“A weed is no more than a flower in disguise, which is seen through at once if love gives a man eyes” – James Lowell

More than four decades ago, I embarked on a botanical journey and started ‘mingling with weeds’. How it began is a story in itself, narrated briefly below. At the Colombo University’s Department of Botany, our Head of Department – Professor, RNDe Fonseka, one day, said at a meeting that funds for “pesticide science” had been increasing. He was well supported in this view by Professor BA Abeywickrama, one-time Vice-Chancellor of the former University of Ceylon, and later, a member of our Botany staff. 

In their view, perhaps, the newest recruit to the staff to strengthen “Ecology” (yours truly), should seek out a pathway (funding and scholarship) to study ecological science through the pesticide-funding theme. I remember this incident well as it was indeed a life-defining moment. The professor’s rather superficial advice was for me to seek scholarship opportunities via the theme ‘pesticides’, which included ‘herbicides’ (weed-killers). The serendipitous moment was when it led me to enter the wonderful ‘world of weeds’! 

I wrote to my future mentors, eminent weed scientists in the U.K., Geoff Sagar, at the University of North Wales, Bangor, and Ralph Kirkwood, at Strathclyde, Glasgow, both of whom delighted in accepting me as a future student. The two had been lifelong friends themselves. The University in Bangor beat the other in processing my application, and I ended up in North Wales. The School of Plant Biology was one of the most prestigious Ecology Schools at that time, under a giant in Ecology – John Harper, Oxfordian don, who established the School, along with his student – Geoff Sagar. Geoff was the Head of the Department when I arrived and John was the much-revered senior, who advised everyone. 

As a new Commonwealth Scholar, joining the Plant Biology Department on 01 October 1980, I prospered, along with many others, under the tutelage of Sagar and Harper. “Weeds were not villains”, they said, “but ‘model’ organisms to understand ecology and population biology”; these are well-known Harperian quotes. 

The three study years (1980-83) were memorable times, as I wallowed in weeds, even as Universities suffered under the ultra-conservative – Margaret Thatcher’s “Thatcherism”, in the U.K. and Ronald Reagan’s ‘Reaganism’ in the USA. The world rapidly became unstable during this period. The most unfortunate and despicable July 1983 riots also burned our motherland, as I hurried towards completing my thesis. Living abroad, at that time, I understood the damage that was done by our politicians to our motherland. I was back on the island one week short of my three-year scholarship towards the end of September 1983.

My doctoral studies may not have moved a mountain. But dealing with a model perennial grass (English couch – Elymus repens) and a brand new selective ‘grass-killer’ (PP006, “FUSILADE®) gave me a great opportunity to explore plant ecology, physiology, electron microscopy, radio-isotopes, and various other techniques. Within 3-years, I worked hard, published well, earned my doctorate, and returned home with a broad knowledge of weeds, ecology chemical control and weed management. 

Thus began a career in teaching ecology, plant taxonomy, environmental science and related botanical subjects, but I never forgot to look at the world through the ‘lens of weedy species’. The high point of my academic career was the launching of the first Master of Science in Weed Science Course, winning a prestigious USAID Research Award of US $ 150,000 and my own Merit Professorship. All of this was while the politics in the country, civilian life, and the Sri Lankan Universities were in utter turmoil, during the chaotic 1987-1990 era.  

However, the instability did not stop me from founding and launching the Weed Science Society of Sri Lanka, in 1990. I received a great deal of help from the industry and agriculturists, especially those in the plantation sectors. The Society established a platform for understanding weeds better and how to deal with them. 

Looking back, three decades later, as a country, we have failed to build on the science and collaborations that had already been established with neighbouring countries in the Asian-Pacific region. As we lurched from one disaster to another, many good opportunities to further this science have been lost, due to incompetence, lack of direction and leadership in science, and institutional apathy. Along with it, the capacity to be sustainably productive not just in agriculture, but also in other enterprises and good environmental management has been almost completely lost in the country. Sometimes, I read that weedy ‘invaders’, species like water hyacinth (Eichhornia crassipes), mesquite (Prosopsis spp.) and lantana (Lantana camara) are blamed for our follies!

The terrorist war in the country, which lasted three decades, should not be an excuse for our malaise and decay in our institutions and the public service, in particular. The country’s governance processes, and value systems unravelled over the past 30 or so years. Broadly, people of all kinds, including politicians, and even the expatriate community, including myself, must take responsibility. 

Some of the lessons from weeds, which I had learned very well and passed on to my students (for instance, adaptability to ecologically adverse conditions, frugal lifestyles, resilience and toughness in the face of human adversaries, attempting lethal solutions, i.e. killing with herbicides), now appear fanciful and irrelevant. 

To add further insults to the decaying country, the worst of the offences were recently committed against the agricultural and plantation sectors, which are so critical to people’s livelihoods and the broader economy. Ignorance and non-science, including the divine providence of “Natha Deviyo”, led to the irresponsible linking of the Chronic Kidney Disease incorrectly to general crop protection chemicals. The banning of herbicides, including glyphosate, and pesticides has devastated the farming communities and productive agriculture sectors. History will record the speed of decay in Sri Lanka’s agriculture and plantation sector as unparalleled.

The push for the whole country to go “organic”, a method that might suit farming on a limited scale but is largely untested on a large scale, is also related to not understanding how ecological systems work and how best to manage ‘man-modified’ systems (cropping fields) and influential factors. “Ignorance was bliss” as the proponents did not realize that “organic farming”, in the modern sense of farming, requires significant and often unsustainable inputs, including energy (machinery, equipment) and labour. Globally, organic farming is really only practised successfully by homestead, lifestyle enthusiasts. It may well be a topic for another day.

Scientific knowledge, including the ecology of natural as well as human-modified systems, so well established and applied, has been ignored. While some scientists left the country, those remaining have been heavily polarized and disempowered as the ugly and non-scientific discourses split them apart. Unqualified persons (including paediatricians and monks) overnight became agriculture ‘experts’. Weeds have much to instruct these people as well, such as ‘co-existence’ and ‘sharing of resources’. 

Paradoxically, some weeds display a “jacks-of-all-trades” behaviour (in Weed Science, some species have a ‘General Purpose Genotype’ that fits many ecological situations). However, I would not be saluting those who destroyed Sri Lanka’s productivity and the social fabric as “jacks-of-all-trades”. They fit more closely to the “Masters-of-None” category of weedy species! 


I embarked on promoting the virtuous side of weeds around 2008-09. It took many decades of experience to make the case for people to appreciate weeds. In 2019, I was instrumental in launching a journal – WEEDS (the official journal of the Asian-Pacific Weed Science Society) promoting a better understanding of the historical aspects of weedy species and our attitudes towards weeds.

As a group of plants, weeds are unloved by some people. However, this dislike is not universal. Weeds are colonizing, pioneering plants, with special botanical and ecological attributes. They are a critical component of Mother Earth’s rich biodiversity. They are also Nature’s Gifts from which humans can learn many lessons. Their special attributes relate to life cycles, growth habits, reproduction and dispersal that allow establishment in any disturbed area, from which they can then easily spread into new habitats. 

From agricultural beginnings, now dating back to well over 12,000 years of man’s history, weeds have been our constant companions. They have followed us wherever humans went as shadows of men. Weeds also spotlight the mistakes man has made in managing our environmental assets.

 Around 2015, I conceptualized a book that would provide compelling evidence of the virtuous side of weeds and their utilization potential, especially for livelihoods and sustainable future societies. The book is now published. 

Some of my reviewers have stated that “It is not just a “garden of weeds”, it is an “orchard”,; rather, it is a “storehouse” of information that would enlighten readers on the history of weeds and how to relate to them more effectively with understanding and empathy. 

As highly successful plants, weeds earned mankind’s wrath, almost as if humans are not able to psychologically cope with other highly successful and ‘pest-like’ species, such as the house fly, European rabbit, European fox, Indian mynah, and a host of others. 

Stories about weeds that are mostly written by non-science writers in popular media, including the internet. They are mostly half-truths, which invoke fear and loathing, instead of a proper understanding. Many species have long been invaluable herbal medicines and food. The archaeological evidence on the utilization of weed species by humans goes back well back to our hunter-gatherer and nomadic ancestors.

Colonizing species are also the ‘ecological ‘Red Cross’, as I explain in the book, that rush to help stabilize and restore lands cleared of vegetation by the human hand or natural disasters. They can also be effectively used in the ecological restoration of damaged ecosystems, such as national parks 

Powerful and emotive phrases like “War-With-Weeds” are commonplace in weed discourses, especially in developed countries, such as the USA, Canada, Western Europe, Australia and New Zealand. This ‘war’ has led to various groups, such as “weed busters” and “weed warriors”, whose efforts at controlling weeds are by and large of limited local success, and essentially, unsustainable in the long term.

More importantly, such viewpoints of antipathy towards weed are not universal. Many African, South American and Asian-Pacific developing Nations and emerging economies are now questioning why weeds are blamed for always being an agricultural production constraint, or why we cannot manage our ecosystems better. Agro-ecology concepts, explained by the author, show that for many thousands of years, humans and other animals have tolerated and ‘co-existed’ with weedy species. 

In the book, there are innumerable examples of weeds that have been crucial to human survival.

Traditional cultures in such societies greatly value species, such as Centella asiatica (Gotu-kola), Alternanthera sessilis (mukunuwenna), Ipomoea aquatica (Kang-kung), Aerva lanata (Polpala), Portulaca oleracea (Genda), Trianthema portulacastrum (Sarana), Basella alba (Nivithi) and a large number of other ‘edible weeds’.

A vast range of ‘healing weeds’ have been known from the times of ancient Egyptians, and include Papaver species (poppies, opium), Cannabis sativus (ganja), Catharanthus roseus (Mini-mal), Datura stramonium (Aththana-Eta), Bacopa monnieri (Lunuwila), Asparagus racemosus (hathawariya), Cardiospermum halicacabum (Wel-penela), Polpala and Gotu-kola. Many species are the only sources of critical, life-saving western medicines, which are used in cancer treatments (such as the vincistrine alkaloids – from Mini-mal), pain relief (morphine, codeine, etc.) or herbal drugs used in the treatment of Central Nervous System (CNS), bladder and kidney disorders.

Colonizing species, such as common reed (Phragmites australis), cattails (Typha species) and even water hyacinth (Eichhornia crassipes) play critical roles in purifying and remediating waterways by absorbing and retaining urban pollutants. Many are important in stabilizing food webs in disturbed environments. 

A vast array of fast-growing species are critical biofuels for rural people (as firewood) and are also biomass for biogas and power generation. The utilization of many species as sources of essential oils, plant dyes and plant fibres goes back more than 5000 years of history.

Powerful and emotive phrases like “War-With-Weeds” are commonplace in weed discourses. In joining unwinnable ‘wars’ against weeds, the public is largely misinformed about weeds with only one side of the story. Some weed scientists and ecologists are also, unfortunately, in this camp. Blaming weeds for human follies of mismanaging our fragile earth is common. Weeds are also called ‘the second greatest threat to biodiversity’ on the earth, a highly contentious viewpoint, within the well-established Weed Science discipline.

Research and teaching, as well as on-ground weed management, over decades, taught me not to deride plant species by calling them ‘The World’s Worst Weeds as some are commonly referred to. Some of these species are, arguably, the best-of-the-best with ecological attributes that can heal the planet and help humans and other animals survive looming uncertain times. To call some species “Invasive Aliens” is a complete myth, pandering to the gallery and not worthy of any deep-thinking scientist. 

The book will surely open a critical dialogue on weeds, across borders that separate divergent views. Can weeds be appreciated for their critical ecological roles? Can they be managed in situations where they may become problematic? 

Human psychology is involved in our responses to weeds. In promoting the ‘virtuous’ side of weedy taxa, I would argue for a better understanding of weeds as part of Nature and ending unsustainable approaches, such as a ‘war-with-weeds’. 

I propose a paradigm shift to tolerate the extraordinarily resourceful weedy taxa (‘living with weeds’) as a strategy to learn and live prudently with all plants and animals. Human cultures and societies would be poorer if we keep treating colonizing taxa as our enemies. 

I am thankful to Robert L. Zimdahl, Professor Emeritus, Colorado State University, USA, for the following testimonials after reviewing the book’s contents:

Nimal Chandrasena recognizes the wisdom of the last lines of the neglected words of Gerard M. Hopkins’ 1918 poem – Inversnaid.

            What would the world be, once bereft,
            Of wet and wildness?
            O let them be left; wildness and wet;
            Long live the weeds and the wilderness yet.

Hopkins and Nimal Chandrasena recognize the error of the mindset of many agricultural people, including many weed scientists – that weeds have no redeeming qualities and must be controlled at all costs.

Nimal says – Wait a minute. Consider whether your weed control views and over-reliance on herbicides may have harmed your science’s reputation. Does your scientific view conflict with the societal view of weedy plants?  Has it harmed your science’s reputation and its public image? 

Read Chandrasena’s book. It may convince you there are other ways to manage vegetation. It may not change your mind, but it will make you think.

The book can be purchased through the Publisher’s Book webpage:


It is priced at Aus $ 32.95 + postage within Australia $ 9.95.

In Sri Lanka, the book will be available from March 2023, priced at Rs. 8250.

The proceeds of this book, written out of love and admiration for weedy species, will only be used for charitable purposes in which the author and others are involved (i.e. Arunodaya Foundation, which is helping Sri Lanka’s disadvantaged). Anyone can contact the author on: nimal.chandrasena@gmail.com

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  • 3

    This article about his book on “Virtuous weeds” is an eye-opener for all of us. It clearly identifies the lack of knowledge of our politicians and bureaucrats including the government officials responsible for agriculture by banning essential chemicals and going organic overnight. Food security has been jeopardised and nobody of authority held responsible and accountable. Experts locally and overseas have been ignored and the system heavily politicised.
    As Dr. Nimal Chandrasena has “conceptualised a book that would provide compelling evidence of the virtuous side of weeds and their utilisation potential, especially for livelihoods and sustainable future societies.” It is suggested that those involved, interested and even laymen read his book.
    As Robert L. Zimdahl, Professor Emeritus, Colorado State University, USA, states,
    “Read Chandrasena’s book. It may convince you there are other ways to manage vegetation. It may not change your mind, but it will make you think.”

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