‘This is a testing ground and a living laboratory’

‘We grow vegetables, research, educate and inform people.’ LAgum is a test site on the roof of Colruyt in Etterbeek, where researchers from ULB gather knowledge about urban agriculture under real conditions. “We nourish bodies and minds.”

The border between the Brussels municipalities of Etterbeek and Ixelles runs over the roof of an apartment block on the Impasse des Moineaux. When the neighboring supermarket, a Colruyt, unveiled plans to expand and demolish the corner building to rebuild almost ten years ago, two local authorities had to give their approval. One, the one from Etterbeek, saw few defects in the demolition and extension project; the other, that of Ixelles, noted a few matters in the margin. They became the seed of a fascinating agricultural project in a densely built-up and busy urban area.

“A minute.” At the top of the stairs to the roof, Guillaume Culot lifts a finger with his free hand. Together with two employees, they fold a metal grid into a dome in the scorching afternoon sun. The pumpkins that are now growing in containers against the eaves, they will lead across, creating a tunnel of green. Culot wipes the sweat from his forehead, pats the rust from his hands and introduces himself as maraicher, which would translate into Dutch as gardener.

He grows vegetables – about fifty different varieties, herbs – about thirty varieties and small fruits like strawberries, raspberries and currants, here in containers on the roof. Part of the profit is processed for hot meals in Refresh’s social restaurant, another part is for members of the roof garden. As with a CSA, community supported agriculture, neighbors and local residents can pay a fixed amount in advance so they can harvest to their heart’s content in the rooftop garden. What is not picked or processed goes to OCMW.

© Lara Laprte
Occupancy compensation

LAgum is the name of the entire project, which has been producing food for the neighborhood here since 2020. ‘That was the most important question from the municipality of Ixelles when Colruyt presented the expansion plans. How do you compensate for the extra hardening? And how do you compensate for the disappearance of a part of the community garden that has been there for ten years anyway?’, says Culot, as he shows me around the curved gardens, where the broad beans hang heavily from the bushes and the heads of lettuce are ready for harvest. I’m surprised how green everything is here after all those weeks without rain.

‘A life had developed around the garden, with people growing vegetables and others finding company. Ixelles wanted to retain this one way or another and made it a condition of the license that Colruyt should equip the roof for exploitation. Not just as a green roof with plants that are good for pollinating insects or that let the rainwater seep slowly down, but a roof where agriculture is practiced’. Culot pulls a carrot out of the ground, wipes the soil on his shorts and cuts off a piece. If carrots could melt on your tongue, they would taste like this, plump and sweet.

Especially in a stone desert like the city, people have lost touch with their food. Finding it here is easy and accessible.

“After a whole series of negotiations, the municipality and Colruyt reached a cooperation agreement. Colruyt would bear the additional cost of the construction of the roof garden, around 300,000 euros, the municipality was given the right of use. And so’, smiles Culot. ‘It’s just become really interesting. In addition to a social project about sustainable and fair food and where people get the chance to train as urban farmers, they also wanted to make it a research project to gather useful, scientific information about rooftop farming. Especially about growing vegetables in containers, so not in open ground, hors-sol, as we say in French. Because if you believe that there should be more space for food in the city, it is important to know what you are doing, what the pitfalls, barriers and limitations are.’

living laboratory

And so the municipality of Ixelles sought cooperation both with the social economic company Refresh, for which Culot was responsible for the gardening courses, and with the agroecology laboratory at the Université Libre de Bruxelles. Together they submitted a file to the European Fund for the Regions, which released an operating budget to link agricultural production and research into this production until 2023.

‘This was a unique opportunity for us to deepen our knowledge of urban agriculture,’ says researcher and biologist Francisco Davila. ‘What is the effect on biodiversity? What about soil life in the substrate, soil that has been worked by humans that humans grow on in containers? Which cultivation method has which result? What about the dividend? The questionnaire we prepared filled itself every day. Yet this roof is a living laboratory. Guillaume discovers a certain moss, a mushroom, an unplanted species, and together we test theories about how and why.’

In the conservatory, where we seek refuge from the increasing wind, Culot points to the withered and curled leaves of the cucumber plant. ‘Influenced by a fungus’, he explains. ‘This year we have more problems with diseases than last year, when we first produced. We’re not sure how that happened yet. Although we know that we have watered more this year. The roof slope ensures that every drop of rain and also the excess irrigation water is collected in a large cistern and pumped up from there when we water further. On paper, it is an economical and efficient system, completely circular. But what if it also makes it easier for us to spread cultures that develop in the warming rainwater over the roof?’

© Lara Laporte

As long as aphids, slugs or fungi do not interfere, Culot will continue to grow. It is important, he believes, that plants themselves build up a resistance or give natural enemies time to settle on the roof garden. Although people sometimes lend a hand here too. “Pigeons were the biggest pest in the first year,” says Culot. ‘This was a food paradise for them. Until we hang Gaston’, he points through the windows of the conservatory to the post between the planters. A paper wake flutters on it, already a bit exhausted from the many swirling in the wind. ‘The pigeons were gone for three days, then they realized that Gaston is harmless.’ A laugh. ‘Don’t underestimate pigeons. Now we put as many nets as possible over vulnerable crops.’

The exciting thing for us as researchers is that this test field is in real time. Drought, hot, frosty days at odd times of the year. It really provides a wealth of information

Green approach routes

The roof garden is surrounded by a gallery of apartment blocks, from which bathrooms, living rooms and kitchens have a view of the activities on the roof. One of the first research questions the ULB team addressed was whether and how pollinators such as bumble bees and bees would find their way to this green spot on a rocky plain. Counting and counting graduate students, both on the roof and in parks, gardens and public vegetable gardens within a radius of one kilometer around LAgum. “We found twenty different bee species on the roof compared to forty elsewhere,” explains Davila.

‘Why less here? We have a few hypotheses. Perhaps because the roof is new, it has not yet been discovered by bees. For some species, it is probably not easy to get there. Green approach routes are missing or they fail to convey the information. The choice of cultivation can also play a role.’

‘Now, for example, we are experimenting with Guillaume with the type of flowers we grow on the overhang. The exciting thing for us as researchers is that this test field is in real time. It is participatory research. In a laboratory and under controlled conditions, the variables are reduced as much as possible. Here you have to make do with the data from the real world. Drought, hot, frosty days at odd times of the year. It really provides a wealth of information.’

Fertile land

His colleague, bioengineer Léna De Brabandere, takes this up. “Another important issue is soil fertility. What is good soil for a roof? But also: how do you work agroecologically in man-made soil? The soil in the bins was there before we got involved in the project. It is a classic mixture of volcanic rock, compost, peat. The latter, for example, are not a sustainable component, they are ancient plant residues that are not renewable on the human time scale. Can we bring such inert soil to life without fertilizer but with compost? The first microorganisms and bacteria are developing. We hardly find mushroom threads for the time being’.

“I saw the first earthworms.” As Culot says it, he bends back and plucks a leaf from a beautiful, meter-tall plant with a purple, plume-like flower. “One of my favorites,” he says. ‘The amaranth. It is a survivor. You can eat the leaves, the flowers, the stem, the seeds.’

This is also a role for the roof garden. Sharing stories about food, introducing other flavors, taking people into what’s blooming and growing and what’s edible.

I bite into the leaf and taste a sharp, refreshing taste. “It’s not a native crop, but when the fields in Canada or the United States are sprayed with round-up, the only one that can survive is amaranth. He’s called a problem. I see it differently. If you can beat Monsanto, you’re a super plant.’ He smiles. This is also a role for the rooftop garden. Sharing stories about food, introducing other flavors, taking people into what’s blooming and growing and what’s edible. ‘Education is essential. Especially in a stone desert like the city, people have lost touch with their food. It’s easy and accessible to find here.’

Innovative processes

But can a roof garden like this with 800 square meters of production area mean more? Can you feed a city of 1.2 million inhabitants and an additional 300,000 commuters a day with your own cultivation? And can the farmer make a living from it? ‘Last year we had a yield of 2.5 tonnes of vegetables. It is important to know that the roof is designed for the experience rather than the return. If they had involved a farmer in the design phase, you would have an area of ​​2 hectares. But even at that scale, in the current economy, where the farmer is a market player but not a price setter, it is not possible to make a living. That is also innovative about this project. I am a salaried farmer. I don’t have to worry about my income or my sales. I can concentrate on innovative processes.’

A roof like this won’t feed the city, but it will feed people in a different way. It provides oxygen, breathing space and it brings people back in touch with the essence of life.

“Of course, you can’t develop these kinds of gardens on all the rooftops in Brussels or any other city. It requires excessive investment, which is not necessarily worth it,” adds Davila. “A roof like this will not feed the city, but it will feed people in another way. It provides oxygen, breathing space and it brings people back in touch with the essence of life. These are functions we fulfill and which are at least as important. Furthermore, we are sitting here on a mountain of information that we can feed to any similar project in any urban area.’

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