16 February, 2025

Blog

Of Weeds & Men

By Nimal Chandrasena

Dr. Nimal Chandrasena

In this short article, I wish to reiterate something I have been promoting for about 20 years, and that is – “Weed Literacy” and “Utilization of Weeds”. As our country has embarked on a “Clean Sri Lanka” new initiative, there is some danger of weedy species being targeted maliciously and unnecessarily for control, leading to disastrous consequences. Some people’s dislike for weeds is understandable. This comes from deeply entrenched perceptions of adverse effects that are attributed to weeds. But not all weeds are bad!

I believe that the GOSL has explained well to the public that “cleaning” Sri Lanka is a broad concept (I hope I am right here) and extends well beyond the literal meaning of ‘cleaning’ the urban, peri-urban and rural environments of rubbish and waste. If this hasn’t been adequately explained, there is a high probability that ‘weedy species’, so badly misunderstood and maligned by humans, will be targeted with untenable control methods.

Therefore, perhaps a brief look into weeds and their relationship with humans may be worthwhile. Just like many animal pest species (houseflies, cockroaches, and mosquitoes are the best invertebrate examples, and rats would be the best mammalian example), ‘weedy plant species’ are shadows of humans; they evolved and followed humans and their habitations. Man is the greatest evolutionary driving force behind the continual, highly successful life of weeds on earth and their future evolution.

My favourite disciplines – Weed Science, Ecology and Environmental Restoration- understand this connection well. We have also taught these concepts and ideas for more than 50 years. However, ‘weed literacy’ is like ‘environmental literacy. Only a few people really care and go that extra yard to understand the underlying historical and ecological causes (human and/or natural disturbances) and factors (such as land-clearing, deforestation and agriculture) that cause weeds to dominate landscapes. I don’t necessarily blame people for being ‘ecologically ill-literate’, but we can do a lot better.

As a former academic and, later, as an environmental science professional, I’ve promoted the utilization of weedy species for the last 30 years. My primary objective has been to explain further what weeds really are, share knowledge and promote a better ‘ecological’ understanding of weeds.

Maligning weeds further would be an unforgivable folly in a developing country like Sri Lanka, which is facing unprecedented challenges in managing food resources for both humans and animals, along with other environmental challenges.

As ecologists, we know that they are pioneers of ‘secondary succession’. That is, they will ‘colonize’ an area disturbed and laid bare by humans or natural forces like wind, water, landslides, earthquakes or cyclones. One thing is certain – these species are not evil colonizers, and as a highly successful group, they will survive any catastrophe that might befall us.

Moreover, many of the world’s crops are direct descendants of these species. Botanists and Plant Breeders know that without such ‘weedy’ germplasm (genes) being available in the ‘wild’, we will not have future crops.

The Sinhala Lexicon helps us understand Weeds better – only if we ‘Listen’

The word – “Colonizing Species” (Weeds) translates to “ආක්රමික ශාක විශේෂ” in Sinhala Dictionaries. But, I find that this literal translation is contextually incorrect in the way weedy species should be described.

A better term is “Pioneering Species” (පුරෝගාමී විශේෂ) – This Sinhala Term is fairly correct in both context and meaning and is titillating to use. The Term captures the ‘virtuous’ side of weedy colonizers, the values of which are what I have been promoting in the WEEDS journal, launched in 2019.

If we in Sri Lanka were to use the Term පුරෝගාමී ශාක විශේශ – it’ll be the very first time such a positive meaning is given to these species in the History of Weed Science! It is a good opportunity, especially for me, to promote their ‘utilization’ for societal benefits.

The term WEEDS – වල් පැළෑටි in Sinhalese, translates to “Wild Plants”. Arguably, it is ‘contextually correct’, but its broader meaning is incorrect (because the Term gives the impression that these ‘wild’ things are USELESS).

The terms ‘Wild Plants’ or ‘Wild Animals’ were constructed and historically used by numerous natural history writers in the past centuries, dating back to the Great Bard – Shakespeare, only to contrast species that were found in uninhabited places. The original ‘weeds’ were those that grew ‘wildly’, in the sense they were not domesticated, contrasted against human-domesticated plants. The ‘weedy’ species grew abundantly, without anyone’s help, adjacent to human habitations. Wherever humans went, inadvertently, they also took with them weedy species.

Another decidedly insightful Sinhala term might be මාර්ගෝපදේශක ශාක විශේෂ which means ‘Plants that show the way!’ If used by the Sinhala lexicon, this Term would again be a first in Sri Lanka! We all know that languages and terminologies evolve all the time. Given this, may I suggest that our Sinhala language experts consider expanding the usage of these terms to give them an appropriate and more meaningful flavour?

Relevance to Food Security, Indigenous Medicine and Biodiversity

It goes without saying that a large number of weedy, edible, herbaceous species are critical for food security in Sri Lanka. The examples of these fast-growing species, which require only little assistance to grow, are far too many to give. But the top four for Sri Lanka would be gotu kola (Centella asiatica), mukunuwenna (Alternanthera sessilis), kan kung (Ipomoea aquatica), thampala (Amaranthus viridis and other species).

The largely forgotten ‘poor man’s cereals’ – best-known as ‘millets’ (Meneri – ‘pearl millet’ – Panicum milliaceum and kurakkan – ‘finger millet’, Eleusine korakana are weedy grasses. They are being seriously revived in India, as I saw and heard about in a recent visit,  while the attention to millets in Sri Lanka has stultified.

Even the well-known ‘thala’ (‘Sesame’ – Sesamum indicum), ‘batala’ (Ipomoea batatas) and ‘maioc’ (cassava – Manihot esculenta) are weedy, fast-growing colonizing (non-grass) species, which grow by seed (sesame) or by vegetative means (batala and manioc). These are critically important world crops; without them, billions of people will starve.

Medicinal weeds also need no emphasis in our island’s cultural history. From our Vedic cultural heritage comes ‘Ayurveda’, dating back 3500 years before now. Abundant Buddhist literature, complemented by Sri Lanka’s own history and culture, is replete with examples that link our societies with medicinal weeds. The salient point is most medicinal weeds in the world are found in disturbed habitats, either inside pristine forests or in the broader vicinity of human habitations.

The reasons are well known and include the short-duration life cycles of the greatest majority of medicinal species. These species, for their own survival, need to produce potent, anti-herbivorous chemicals, many of which are of medicinal value to both animals and humans. If such chemicals are not able to deter foraging herbivores, grazing animals will graze the weedy species to oblivion.

Many weedy colonizers are essential and indeed critical bioresources for animals, such as the flowers they produce for bees and birds and forage for large animals, like our elephant population. ‘Gandapana’ (Lantana – Lantana camara) was introduced by the British rulers accidentally to Ceylon in the mid-19th century. It is a globally important weed that produces incredible amounts of nectar. Without large amounts of sugary nectar, many insects – bees, moths, butterflies, etc. and bird species will suffer.

Another good example is ‘Guinea grass’ (Panicum maximum). Recognized even by the Romans as a crucial animal fodder, the updated and revised botanical name is Megathyrsus maximus. Widespread on our island, it is one of the primary food resources for elephants in all of our nature reserves. I have personally observed how elephants feed on Guinea grass, hours on end, at Wasgomuwa, Udawalawe and other reserves. Just imagine the plight of our noblest of animals – if we start taking Guinea grass out under the “Clean Sri Lanka” program?

Massive amounts of Guinea grass also protect our Central Highlands from the severe erosion they face (due to excessive land-clearing for plantations). It is one of the most useful species that the British rulers introduced to Ceylon in the latter part of the 19th century, from Guinea in West Africa, by the British as fodder for their horses.

Water hyacinth, the infamous ‘Japan Jabara’ (Eichhornia crassipes), is another brilliant example. The vernacular name – ‘Japan-Jabara’ is a misnomer. The French botanists, sponsored by Empress Josephine (Napoleon’s wife), made extensive introductions of water hyacinth to Africa after Alexander Humboldt, the German explorer, found water hyacinth in Brazil. The idea was to beautify water gardens in Africa.

The British, then, introduced this extremely fast-growing species at the beginning of the 20th century to cover Colombo’s lakes (Beira) and other waterways as a deterrent to Japanese aircraft from attempting a landing. That’s house ‘Japan Jabara’ came about. By 1906, it had completely covered the lake and surrounds to such an extent that the rulers brought in legislation prohibiting its import. Since then, it is a prohibited species, but nothing could stop the spread of water hyacinth away from Colombo into other water bodies.

Much maligned water hyacinth, which dominates the large and small lakes in Africa and a vast amount of waterways in India, Thailand, Malaysia, Vietnam, Philippines and Indonesia, is now undergoing a global revival as a species that can alleviate poverty, provide income for rural women and children. It is a vital part of reviving rural economies, livelihoods, eco-tourism, and cottage industries, and its biomass can also be converted easily into biogas (renewable energy) and fertilizer.

Not so long ago, someone in the Environmental Authority asked me about using water hyacinth as a bioresource in Sri Lanka. My cautious answer was that ‘we do not have sufficient amounts’ for a sustainable industry base’.

Suppose we started harvesting water hyacinth in Sri Lankan water bodies and convert it to a useful bioresource, in whichever form is appropriate. In that case, I do not think there will be much left after a few years. Presently, water hyacinth’s magnificent, purple-coloured flowers are the most common flowers offered to temples at Anuradhapura. In recent visits, I’ve seen many people plucking the flowers from the ancient waterbodies and providing a continuous supply. I’ve also seen some coarse paper that has been made with biomass.

There are many other beneficial effects of weedy species, including the pollination benefits of the ‘wildflowers’ and their utilization in stabilizing and improving wetlands and waterways, as well as damaged landscapes. As many species produce large biomasses fast, they are part of the sustainable ‘energy mix’ solutions we require. The Indian Railways has been investing millions of rupees each year for farmers to cultivate ‘Endaru’ – Castor Oil plant (Ricinus communis) on marginal lands, otherwise unsuitable for cropping. Castor Oil is an important component of biodiesel used by the Indian railways, and ensuring a continuous supply from a weedy species is the right decision.

Sri Lanka’s relatively small landmass does not allow us to ‘grow’ most weedy species as bioresources. If anyone thinks so, they’d be wrong. However, weedy species do perform admirable functions in the island’s varied ecosystems. A better understanding of weeds can be obtained using the Sinhala terminology, as I’ve suggested. It might irritate some people, but it would be enlightening as we embark on ‘cleaning’ our living environments and also look for sustainable and practical solutions to improve the lives of our people. It is time for the country to open our minds, ‘re-think’ how we can ‘live with weeds’ and most importantly, have this discourse.

*Dr. Nimal Chandrasena – was a former Associate Professor of Botany (Weed Science), University of Colombo, Sri Lanka. He lives and works in Perth, Australia and is also the Editor-in-Chief of the international Journal – Weeds. Nimal is also the author of “The Virtuous Weed”, published in 2023.

Latest comment

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    In reality, every plant can be a weed or a good herb; it just depends on where it is and how it is used. So, there is intrinsically no such thing as a weed.
    Even காதல் புல், a “weed” if there is one, can be a medicinal herb in some circumstances.

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