Learning from Japanese Knotweed in Brussels’s Feral Wetlands

This essay on Brussels’s “feral” wetlands and Japanese knotweed is the fourteenth installment of the Botanical Imaginations series, which complicates, diversifies, and proliferates the stories we tell about plants. Series editors: Laleh Ahmad, Tessa Archambault, Dylan Couch, Ellie Kincaid, Rebecca Laurent, Kayleigh Lobdell, Clare Michaud, Nicolás Felipe Rueda Rey

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Japanese knotweed (Fallopia japonica) took me on an unexpected journey. I was doing graduate fieldwork in the post-industrial part of Brussels, where factories closed doors following deindustrialization. Within a few of these remaining abandoned spaces, unique, feral wetlands were born. In 2007, one year before the financial crisis shook the world, such a waterbody emerged on the grounds of the former Wielemans Ceuppens Brewery.

I wanted to conduct a multispecies ethnography of these wetlands, but as my research progressed, nothing seemed to stand out. Only gradually, as I went through interviews and photographs, one plant caught my attention: Japanese knotweed. I had been photographing it from far and close, and the people I met had repeatedly shared stories about the plant. Yet, I had remained unaware of its significance.

I had fallen prey to what botanists call plant blindness: the tendency to miss plants because we perceive them as a passive backdrop rather than as actors in the world. Scholars of the plant turn suggest that plants are world-making beings whose specific plantiness shapes the world we inhabit. Gradually, Japanese Knotweed appeared to me as a protagonist, shaping her own part of the story.

Walking Brussel’s Feral Wetlands

Many of those I had the chance to walk with by the city’s feral wetlands shared that the wetlands became a source of strong attachment. They taught me to see these not as “empty” or “unproductive,” but as living, relational spaces. Their uselessness, as perceived from the perspective of urban developers, might be what allowed them to become sites of refuge, where unexpected forms of coexistence have arisen. Matthew Gandy also unsettled the idea that brownfields simply await redevelopment, believing that attuning to the independent agency of nature would nurture a new understanding of the city.

Residents caring for these wetlands described these landscapes differently than city planners as well as the regional environmental authority. Their relation to Fallopia Japonica was no exception.

In these urban spaces with an ambiguous ontological status—neither park, nor natural reserve, and mostly invisible on official maps, environmental narratives become blurred. I found myself inhabiting what Donna Haraway calls the “pleasure in the confusion of boundaries,” where binary-based thinking begins to unravel.

I talk of these waterbodies as feral, in the same way as residents do, to acknowledge how their water escaped domestication and reverted to a state freed from human control, even if only temporarily.

These emerging ecosystems evolve on a terrain shaped by successive attempts to govern water and order life along the river. Long before the nineteenth-century covering of the Senne, the river and its tributaries had been channeled and harnessed through an extensive network of mills, fishponds, and waterways. These interventions never fully mastered the watershed. Flooding and silting continue to unsettle human ambitions in a city that always negotiated water’s presence.

Remembering the Watershed

Watershed, noun
[ C ]   a high area of land where rain collects, flowing down to supply rivers, lakes, etc., at lower levels.
[ S ] an event or period that is important because it represents a big change in how people do or think about something

Residents shared with me their longing for the marshy landscapes that predated the industrial suburbs in the Senne River Valley. They expressed grief for their disappearance and anger towards the violent speculation and gentrification which continues unbridled. Activists work tirelessly to safeguard Brussels’s urban nature, which is able to return to the city’s interstices when they fall into disuse.

Valeria Cirillo and Allan Wu Wei invite us to think-with the return of water to the ruins of capitalism.  For them, urban, feral wetlands constitute an urban resurgence. 

After the Wielemans Ceuppens Brewery closed its doors, new foundations were laid to redevelop the site. The groundwater table was accidentally broken, and, as a result, water resurfaced. With the financial crisis, construction came to a halt and a spontaneous process of rewilding began. 

Over the last ten years, this “urban wasteland” and hide-out became habitat for migratory birds and a home to many species, from amphibians to insects and macro-invertebrates to micro-organisms. Its continuous transformation over the seasons also nurtures a collective imagination, inspiring cultural and science initiatives as well as artistic and creative endeavors. Today, this unlikely place is known as the Marais Wiels (the Wiels Marsh).

In Search of Lost Names

Over the years, what seemed like the result of a flooding—and no more than a large puddle to most—became a source of attachment for a few. One such group, the Fairies of the Marsh, formed to resist redevelopment projects. 

To protect the wetland, they gave it a name. The name Marais Wiels intentionally evokes Brussels’ origins, recalling its etymology as “a settlement by the marsh.”

The act of naming was in itself a radical gesture of imagination and of advocacy, which recognized these water bodies have a personality, an identity.

In an age when the names of so many species and natural sites are vanishing from our vocabulary and memory, this act reveals the power, creativity, and intimacy of naming what surrounds us. Still partly threatened by re-development, the wetland’s future remains uncertain. But still, signs near the water read: “The marsh exists.”

Tracing Japanese Knotweed’s Journey

If naming the city’s threatened wetlands contributed to acknowledging their existence, the names I encountered for Japanese knotweed reveal a different politics.

Known scientifically as Fallopia japonica and often called Polygonum cuspidatum or Reynoutria japonica, Japanese knotweed, known as Itadori (虎杖) in Japan, is a rhizomatous perennial native to East Asia. On the slopes of Mount Fuji and Taiwan, it is a pioneer species which grows on barren, disturbed terrain: volcanic ash and recent lava flows.

The name Itadori can be translated as “take away pain,” an expression of its long history as a traditional medicine in Japan, China, and Korea.

Itadori has been one of the most familiar wild plants to Japanese people for centuries. For thousands of years she has co-evolved with the beings inhabiting her home range, including plants, fungi, animals, and people.

The plant traveled to Europe with Philipp Franz von Siebold, a German physicist and botanical collector. As a military physicist, Siebold traveled extensively. Charmed by her aesthetic qualities, he collected fragments of knotweed and shipped them back to the Netherlands from Dejima, Japan, an artificial island and Dutch trading post near the city of Nagasaki. The island was the only point of contact with the outside world during the isolationist Edo period.

As a newly introduced plant, Itadori circulated amongst collectors and botanical gardens, who celebrated her ornamental and horticultural appeal. 

The plant’s journey reflects how interwoven botany and imperialism are. Modern botanical science resulted from colonial expansion, during which techniques of classification, extraction, and transplantation were developed to control and profit from territories and their inhabitants.

Among the thousands of species transported across the globe through the expanding networks of empire, trade, and scientific exchange, Japanese knotweed has become one of the most difficult to control. Forming dense monocultures through clonal growth and occluding sunlight, she outcompetes native plant species. She reduces plant diversity and alters soil chemistry and microbial communities, even affecting invertebrates. She also decreases soil fertility for surrounding plants by using up the soil’s nutrients.

Beyond her impact on biodiversity, her rapid spread concerns landowners as she complicates redevelopment projects and, in some circumstances, has even lowered private property values.

The Politics of Weeds

The way we name plants reveals our stories. Japanese knotweed is often described using militarized language. She is said to invade, colonize, spread aggressively, or threaten native ecosystems. We often paint her as “out of place,” creating a botanical “other.” This othering, however, may occlude possibilities to see beyond essentialist labels, alienating the plant from her deep history and local ecology. 

Knotweed’s weediness, then, is an invitation for us to listen to the stories which plants on the move might have to tell, entangled as they are with our own histories. As others have argued, “invasiveness,” is not a property of specific species. Environments become more “invadable” due to colonial and capitalist histories of extraction, degradation, and disturbance. In this sense, to be a weed is a relational, political phenomenon. 

The management of invasive species occurs within the broader context of biodiversity collapse, where ecosystems are profoundly shaped by urbanization and further destabilized by climate change. In this context, Japanese knotweed and other well-known “weeds” are auto-rewilders—species that flourish in human-disturbed environments, particularly well adapted to the fragmented landscapes we have left behind.

Encounters with Itadori in Brussel’s Wetlands

Learning the names of plants and animals is a powerful act of support for them. When we learn their names and their gifts, it opens the door to reciprocity.
—Robin Wall Kimmerer

As an uprooted pioneer species, Itadori can be found along waterways, railways, and in areas where soils are polluted with heavy metals. Her heart-shaped leaves and tall reddish stems are familiar to those who wander such liminal places. The plant, however, arrived to me first through the sound of its name.

It was a warm summer afternoon. An artist with long, silver hair braided down her back guided me along the water at the Marais Wiels. Pointing to a plant at our feet, she said: “This is Japanese knotweed. It’s a plant I really like, but it’s invasive.”

I did not think of Japanese knotweed again until I returned to the wetland later that summer. A young photographer drew my attention to the plant again and told me: “It completely fucked up native species. And at the same time, it grows like chamomile on our polluted soils.” She mentioned its edible shoots and their tart, sour taste, and another, gentler name emerged: “wild rhubarb.”

In a nearby wetland threatened by redevelopment, the Marais Biestebroeck, Japanese knotweed had recently become a legal obstacle to real estate development, and therefore an “ally” to those opposing it. Today, 75 percent of the wetland is planned to be built upon by private real estate investors—in an area that concentrates social and ecological injustices. 

Here, in the old Broekbeek valley, where the Atlas Brewery still stands, water emerged on a brownfield too. Located on the former warehouse site of Shell, the water emerged during decontamination works.

A naturalist who advocates for the natural spaces of Brussels agreed to have a conversation. Walking through the wetland with them was like traveling through time. Once known as the “Shell Island,” the waterbody was renamed by those who carry the memory of the water. The Marais Biestebroeck (the Biestebroeck Marsh) is seen by residents as another example of resurgence, and its name recalls the old Broekbeek stream, which according to the naturalist, might have been flowing near where we stood. To name, then, is to participate in a collective act of faith in restoring not only the ecological functions of landscapes and ecosystems, but also our own memory of them. 

While butterflies flew around summer blooms, we took refuge in the shade of young trees. The naturalist turned to me and said: “The paradox is that the marsh was temporarily saved by the most worrying plant of all: Japanese knotweed.” She had become an unlikely ally because controlling the plant’s spread can only be done at great expense to developers.

In Brussel’s abandoned interstices, new assemblages, relationships, and ways of seeing emerge. As a result, contested wetlands have become epistemic laboratories where new attachments flourish. When dominant environmental regimes of control are temporarily halted, encounters between people and non-humans and traveling concepts such as “alliances” open the possibility of co-becoming: of being changed, however slightly, by other beings and the places we inhabit.

Lessons from Itadori

And the point is, to live everything. Live the questions now. Perhaps you will then gradually, without noticing it, live along some distant day into the answer.
—Rainer Maria Rilke

The ways people see the future of these feral wetlands are diverse, ranging from a new type of natural reserve nested in the city, to institutionalized and standardized recreational areas. In my conversations, many spoke of a future in which invasive species would be removed. The aspiration to recreate pristine, wild landscapes stems from a Western neoromantic vision of Nature, which has underpinned the environmentalist movement since its very beginning. 

I rejoice in having met these contested wetlands and a plant such as Itadori.  It is when we do not know, when we are not grasping towards conclusions, that we can discover something new. As we grapple with the recognition that new ecological communities are becoming a feature of this rapidly changing world, my journey with Itadori was a gift.  She showed me the importance of paying attention, so that we can be deeply present and find doorways to new imaginaries. Itadori led me to reconsider the city as an adaptive environment, one that could be founded not on extractivism, but on principles of coexistence, repair, and reciprocity.

Osaka-based photographer Koichi Watanabe followed Japanese knotweed over the world for an entire decade. His work resulted in an exhibition and book entitled Moving Plants. I had just finished my fieldwork when I came across it.  His book briefly refers to the Yi Jing (Book of Changes), one of the oldest Chinese texts, originally a manual of divination. Thousands of years old, the Yi Jing continues to stand as a reminder to see the world as interconnected, alive and constantly changing. Watanabe’s work is a reminder to notice, remember and feel the life force which runs through our world. 

Ultimately, my encounter with Itadori in Brussels’ feral wetlands offers no easy answers or conclusions. It offers instead an invitation: to allow ourselves and our language to be transformed by the aliveness of the landscapes we inhabit.

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Featured image: “Dusk.” Marais Wiels, Brussels. Image by the author, 2026.

Louise Bazelaire is a Master’s student in Nature Conservation at Wageningen University, currently working as a Nature Restoration Intern at IUCN in Bonn, Germany. She completed a B.A. in Anthropology and Sociology at the Université libre de Bruxelles. Louise’s work draws on sensory ethnographic research, photography, and digitized archival materials to listen to and trace the memory, stories, and relationships that shape landscapes and those who inhabit them. Nourished by artful research practices, she explores the possibilities of co-existence between plants, water and people, cultivating forms of attention that unsettle inherited ways of seeing. Instagram. Contact.