---
title: "Balcony plants against the heat"
description: "Plant biologist Matthias Erb explains how a University of Bern project and the spin-off Boum are greening the Postgasse in Bern’s Old Town against urban heat."
url: https://unibefoundation.ch/en/blog/balcony-plants-against-heat-urban-greening-postgasse
updated: 2026-09-16
---

# Balcony plants against the heat

> Plant biologist Matthias Erb explains how a University of Bern project and the spin-off Boum are greening the Postgasse in Bern’s Old Town against urban heat.

Blog

10. January 2024

# Balcony plants against the heat — urban greening in the Postgasse

#### **In brief:**

In Bern, prolonged heatwaves and heavy rainfall are no longer exceptions. In recent years, we have been able to witness these effects of climate change in the city. But what solutions are there to address this issue? Plant biologist Matthias Erb gives us an insight into a project launched by the University of Bern that aims to counter heat in cities, and explains what each of us can do to contribute.

#### **Narrow cities — hot summers**

More and more people live in cities. Due to their high consumption of resources and their considerable production of waste and greenhouse gas emissions, cities have a major impact on environmental problems. But they are not only significant contributors; they are also affected by climate change as victims. This summer, too, the effects of climate change were noticeable in the city of Bern: although we enjoyed swimming in the Aare in October, it left a bitter aftertaste. Swimming in the Aare in October? Somehow that is not normal. While we queued at the Aarestägli in the hottest months, the lanes of Bern’s Old Town remained comparatively empty. Why? The dense buildings in cities store heat, which places an increased burden on city residents – including in the Postgasse.

A research project at the university is looking for solutions to keep summer in Bern’s Postgasse bearable for residents. Since May 2023, an interdisciplinary project group has been greening the Old Town lane together with its residents in order to counteract climate change. The University of Bern spin-off [Boum](https://boum.garden/), which has developed a pot system with fully automatic irrigation, is also involved. Matthias Erb initiated the project in the Postgasse and also plays a key role at Boum. The UniBE Foundation specifically supports research that puts sustainability and innovation at the forefront. That is why we met Matthias Erb today at Boum’s office in the Länggasse to find out what has happened in the Postgasse and what it looks like today.

## **Interview with Matthias Erb** [\#](#interview-with-matthias-erb "Direct link to Interview with Matthias Erb")

**UniBE Foundation: Professor Erb, you are closely involved in the greening project in the Postgasse. Why are cities of particular interest in view of climate change?**

55% of the world’s population already lives in cities. In the future, almost all of us will be urban. Cities are incredibly fascinating and efficient systems, but they also have huge sustainability problems. They heat up twice as fast as rural areas. They are also poor in nature, and the quality of life for city dwellers is often relatively low.

**What is the vision behind the project?**

By bringing plants into the city, we solve several problems at once. Plants have a cooling effect on the environment and provide habitats for pollinators, birds and insects. We humans also benefit from them. It is scientifically proven that plants reduce stress and make us healthier and happier. The vision is therefore that the cities of the future should be much closer to nature, which in turn directly increases the quality of life and the sustainability of these spaces and of nature.

**What role does Boum play in this project?**

Boum shares this vision. Boum is a spin-off of the University of Bern that we founded with the idea of creating a planting system that enables everyone to grow and enjoy plants successfully at home.

> *Cities are incredibly fascinating and efficient systems, but they also have huge sustainability problems.*
>
> Matthias Erb

If we manage to bring such a system to people with Boum, we will also make cities greener by enabling people in urban areas to green their balconies, terraces and entrances. This naturally makes collaboration with the research project an obvious choice. Boum serves as a vehicle for enabling this transformation.

**What attracted you to this challenge?**

Doing something for the green cities of the future appealed to me because it is an important challenge: it is very topical and will be much more important in the future than it is today. It is my attempt and my intention to make a positive difference in the world.

**Why the Postgasse of all places?**

As a street, the Postgasse is highly interesting, but also challenging. It is almost completely sealed, which makes it incredibly hot. It is also a listed heritage site and densely populated. New buildings can be equipped with green flat roofs or green façades, but very little has been tested so far on how historic city centres, which cannot be altered, can be greened. Greening the Postgasse was therefore an exciting challenge.

**How did the people in the Postgasse react to this project?**

They were very enthusiastic. The city was also positive about the project. The planting day at the start of the project, in which various business partners took part, was a special experience that gave us a lot of energy. It was a great day, and many people came.

**The project was launched a year ago. What does the Postgasse look like today?**

The lane is noticeably greener. The people who took part have also contributed to this change. You can see that when you walk along the Postgasse today.

**What successes can you look back on?**

The greening has brought some remarkable results. A survey of residents revealed that 80% of them perceived their quality of life to have improved significantly. There were also many observations of nature. A large proportion of residents would like the project to continue and have expressed their willingness to remain actively involved. We were also able to observe that certain areas of the lane became cooler. To cool the entire lane, however, considerably more greenery would be needed. In any case, it had a positive effect on the overall atmosphere in the lane.

**What obstacles are there?**

One thing to bear in mind was certainly that a lane is both a private and a public space, which is why many different interests come together that have to be taken into account. We had to clarify the project with the event managers and the civil engineering office and look at our scope for action. But since everyone agreed that the project was a good thing, that went relatively smoothly. Plants are a good thing – everyone probably agrees on that.

**What are the next steps for the project?**

The project will continue for at least another year. During this time, we want to take a closer look at the development
of the greenery and at long-term effects.

**What concrete impact has the Postgasse project had on Boum?**

The project has certainly helped to increase our visibility. The press is interested in projects like this. The nice thing is that the project links university research with partners from business and the public. In this way, we work together with the residents on a shared vision.

**The project aims to green urban spaces. What can each of us do to create greener spaces and make a contribution?**

The simplest thing is to green your own space: everyone has at least one windowsill. Nothing stops us from greening it. In doing so, we do something for ourselves, but also for sustainability. There are also other options, such as getting involved in a neighbourhood association or at a political level. Supporting research at the university and similar institutions is also very important. That is probably where you have the greatest leverage, because that is where solutions with global potential are developed.

> *Supporting university research is very important. That is where solutions with global potential are developed.*
>
> Matthias Erb

#### **Hopeful about the future**

An hour later, we say goodbye to Matthias Erb and his team, who are preparing for the spring season at the office. On site, he shows us how the Boum system also works indoors.
The automatic irrigation allows houseplants to grow optimally with minimal effort. Despite the climatic challenges ahead, our visit to Matthias Erb leaves us looking optimistically towards a greener urban future.

### About the researcher [\#](#about-the-researcher "Direct link to About the researcher")

**Prof. Dr Matthias Erb** is Professor of Biotic Interactions, Director of the interfaculty research cooperation One Health and Co-Director of the Institute of Plant Sciences at the University of Bern. He has received several awards for his research on interactions between plants and their environment. He is also a co-founder of the spin-off company Boum, which was launched in 2021.

### About Boum [\#](#about-boum "Direct link to About Boum")

[Boum](http://www.boum.garden/) is a University of Bern spin-off founded in 2021. Using an interdisciplinary, scientific approach, it has developed a user-friendly pot system based on ecological and technological knowledge. The pots contain a substrate made from by-products of Swiss forestry and agriculture that was developed specifically for irrigation. The irrigation is fully automatic and solar-powered.

### About the project [\#](#about-the-project "Direct link to About the project")

The interdisciplinary research project in the Postgasse in Bern’s Old Town started on 6 May 2023. The aim of the project is to find out to what extent sustainability problems in urban areas can be tackled through participatory greening. Together with various scientific, business and cultural partners and the residents, the lane was planted for the first time in the summer. The effects of the plants on the urban climate and on the neighbourhood’s residents were also observed and measured.

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