Berlin Mapped 900,000 Street Trees and 12,000 Volunteers Showed Up to Water Them

Berlin has around 900,000 street trees, and now there’s an app that knows every single one. Gieß den Kiez, built as an open-source project, maps trees by species, age, and thirst level so residents can see exactly which ones need water and when. The result? 12,000 volunteers signed up to help city maintenance crews keep them alive.

One of those volunteers is Amanda Gläser-Bligh, who waters a linden tree on her street with 20 liters a week through the hot months. She named it Linda. Her devotion isn’t unusual in Berlin, where tree care has quietly turned into a neighborhood habit.

Project lead Anna Mehrländer said she was surprised by how deeply people care about trees, adding that the app gave willing helpers the permission and structure they needed to act. That’s the takeaway for other cities: the concern already exists, people just need a clear way to channel it. What’s one tree on your street you’d commit to this summer?