Not many designers enter into their work by falling in love with a plant. And Japanese knotweed is not just any plant; it is one of the most charismatic villains of the vegetal world. Successfully colonising the continents by casting its roots from Japan to the US, other parts of Asia and Europe, it is known as one of the most invasive plants on Earth and a serious threat to biodiversity. Simultaneously, knotweed is gaining attention as an exceptional medicinal plant, a tasty substitute for rhubarb and a late-summer food source for foraging pollinators. So, why not also consider this omnipresent pest as a local resource to produce paper?

Harvesting knotweed to create an urban paper product line brought us closer to feral ecologies where invasive plants thrive. Such ecologies can be found on abandoned construction sites, railway routes and highways or neglected ruins; man-made spaces that have usually been disturbed by large-scale machines and extensive infrastructural projects. Containing unexpected assemblages of construction materials, native and exotic species, and feral lands trigger our curiosity and imagination.

A contractual agreement with the site manager – the Ministry of Justice – paved the way for reopening the neglected public land. The act of cutting through a construction fence to install the door not only reintegrated the space into the urban fabric but also brought the site back into the public’s collective imagination. However, as visitors entered this remarkable urban space, a crucial aspect came to light: public access cannot be assured at all times. Signs posted at the entrance remind visitors to respect the vulnerable urban fabric, emphasising its role as a place of multi-species care and repair. Krater is a sensitive site that hosts the flourishing and decomposition of many pioneering species, revitalising once abandoned grounds. It houses various multispecies interactions, such as providing nesting grounds for birds and food for pollinators, fostering soil formation, facilitating insect communication, and enabling winter hibernation. Despite, or perhaps because of, its inaccessibility, Krater is a feral typology of a public green space maintained by a collaborative effort involving creatives, ecologists, plants, soil, animals and other participants, rather than relying on city mowers and machines.

The Krater collective is a group of transdisciplinary enthusiasts who were courageous to reinvent their respective professions, studios and working conditions to act as guardians of a rewilded ecosystem at the pending construction site in Ljubljana. Since Krater’s ecosystem is constantly on the verge of extinction, they cultivate creative resilience in the face of urgency by inventing wild tactics, events and formats, treating administrative constraints and other restrictions as the subject of artistic interventions. This action calls for unexpected alliances and inventive economies to open up new fields of regenerative, relational and critical creative practice. Alongside site-specific work such as the cultivation of biodiversity, Krater hosts internationally acclaimed educational formats to introduce new typologies of work into human culture (The School of Feral Grounds), laboratories to experiment with biomaterials (“NotWeed” paper, invasive plants, mycelia and wild clay), advocacy strategies (banquets, mediation processes, public speeches), exhibitions (Forbidden Vernaculars BIO27, Feral Occupations GB35), conferences (The Feral Palace), and other public programmes (Krater Vibrascapes, harvesting Japanese knotweed, Feral Cartographies Cycling, Tea Ceremonies, Little School of Urban Ecologies, etc.). Krater was a finalist at the New European Bauhaus Prizes in 2021. In 2023, the project received a special mention at the 35th Biennial of Graphic Arts in Ljubljana and the highest Slovenian accolade bestowed on architecture for public spaces: the Plečnik Award.

In paper laboratories, we experimented with manual paper-making processes, creating samples from invasive plants such as thorny Robinia branches, Canadian goldenrod and Japanese knotweed stems to test them for industrial production. Paper attracted our attention as one of several materials that are becoming increasingly popular in various sustainability-driven applications. With the ban of many plastic-based products and the rise of online shopping, the demand for paper has increased drastically in Europe. According to the Food and Agriculture Organization, tree plantations have expanded by 50% in the last thirty years, greatly increasing the threat to terrestrial biodiversity. "Notweed” paper, which is locally sourced from invasive plants, was introduced to enable designers to contribute to material practices that reconnect people with the local landscapes. By harvesting the abundant Japanese knotweed, usually known as an unwanted pest that must be eradicated, we created a sustainable paper alternative. Replacing virgin wood cellulose from tree plantations with knotweed fibres has established an economy that not only yields a local product from ‘unwanted material’ but also challenges warlike strategies centred on invasive species and engages the local community in learning about damaged ecosystems. Importantly, producing “Notweed” paper diversifies the collective’s income by reducing its reliance on competitive public funding and supports economic resilience in our eco-social design activities.

Sustainability in design is not just about inventing new products from local materials and waste products, or curating ecological themes. To be truly sustainable, it also means recognising and critically examining the reproduction of inequalities at work, in nature and in our culture. To sustain its public presence, Krater frequently contributes to biennials, exhibitions, workshops and guided tours. However, these institution-led activities often fall short in providing the support needed for the collective to survive in the long term.

The Banquet of Feral Occupations, organised as part of the public programme of the 35th Biennial of Graphic Arts, was hosted to explore new paths of solidarity between public institutions and the independent scene. Delegates from institutions and NGOs, alongside the Krater collective and attendees of the 35th Biennial of Graphic Arts, gathered in the rewilded construction site to discuss what needs to change if we want to preserve Krater’s creative practices for the future. As a platform for bottom-up diplomacy, the banquet proposed funding tactics to ensure that urgent discourses continued, strengthened alliances and introduced novel legal entities for preserving wild urban sites. One prominent question that we addressed focused on the protection and creation of new public green spaces in the city amidst rapid urbanisation and the influence of capital-based interests.

While Krater continues to flourish as an urban commons, it is considered an unregulated area by Ljubljana’s city authorities, whose approach to environmental regeneration and community engagement is undergoing scrutiny. The general urban plan categorises the Krater ecosystem as suitable for development, while a golf course on a former waste dump, and the Roma community’s relocation in favour of a leisure park, are promoted as “green regeneration”.

The Krater case is not the only one of its kind: there is a recognisable practice of encouraging urban regeneration by cleaning up unsightly messes (whether invasive plants, urban nature, civil initiatives, squatting or homelessness, etc.). Seeing Krater not as a plot of land limited by its administrative boundaries, but as a node in a web – a connector enabling multiple species to transit Ljubljana – is crucial to stop the further fragmentation of the city’s green spaces. The main problem with the radical erasure of such sites is that this cuts off the routes used by wildlife. When we design urban green spaces that are not close enough, large enough and biodiverse enough, urbanisation contributes to large-scale species extinction.

You can find the Krater Collective on Instagram, Facebook and the Internet. You can learn more about the Notweed paper here.