Gieß den Kiez, an open-source project run by CityLAB Berlin, maps more than 900,000 Berlin trees in real time and flags those in critical need of watering. The interactive map calculates each tree’s water needs from age, species and local rainfall, shows the last time a tree was watered, lets volunteers log waterings and uses colour-coding to prioritise saplings and other at-risk trees. Amanda Gläser-Bligh adopted an eight-year-old linden in Charlottenburg through the platform and waters it weekly during heatwaves. The project launched in 2020 and now has about 12,000 registered volunteers whose efforts supplement district street and green space authorities that cannot always keep up. Gieß den Kiez provides practical guidance on correct watering technique, collecting rainwater and the locations of Berlin’s water pumps. Usage spikes in hot weather; nearly half a million litres were poured soon after the platform launched and on 27 June, when Berlin hit a record 39.9C, volunteers delivered about 8,000 litres across the city. The code and approach can be adopted by other heat-stressed cities seeking coordinated, community-led tree care.
