The city of Erlangen has been using digital sensors for a year to protect its urban trees from drought. The moisture sensors measure the soil moisture and transmit the data to a digital twin of the tree. This allows the actual watering requirements of each tree to be determined precisely, saving water and driving distances. The system thus helps to minimize drought stress for trees. Due to the positive results, this project was extended and also used in other cities such as Bamberg and Berlin to promote sustainable care of urban trees.