Urban trees often have problems in technogenic soils. Modern construction technology means that there is little root space, trees stand in the middle of engineering structures such as roads and cable routes and the subsoil is becoming increasingly compacted due to vibrations and shocks. Urban and street trees in Zurich have to withstand these and many other challenges on a daily basis. Tree substrates are the basis for the healthy growth and long life of trees in urban areas. From a vegetation point of view, they should provide urban and street trees with sufficient nutrients and at the same time allow access to water, air and pores. According to the FLL (Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau e.V.), the design of the plant pit can be divided into a buildable and non-buildable form. Depending on the planting location, single or multi-layered substrates are required. With the appropriate tree substrates, the roots should be ‘directed’ into the depths or under neighbouring traffic areas. On the one hand, this improves the stability of the tree and on the other hand, the roots have more access to water, which is essential with the future development of the urban climate. In addition to new installation techniques, new structure-rich substrates are also required for these new requirements. Grün Stadt Zürich commissioned the Zurich University of Applied Sciences (ZHAW) to revise the current formulation of the GSZ tree substrate. The result should contain an improvement or upgrading of the current recipe, including supplier details (origin) and prices (including delivery). One component of the results should be a revised recipe with grading curve and ideal soil-physical properties in accordance with the specifications (FLL guidelines (grading curves) and Vegtra Mü). The aim of the project is to adapt the current GSZ standard tree substrate, which can be built on, in order to reduce the floating of the expanded clay and the silting up of fine particles. As part of the project, different substrate components were therefore compared and developed into a new tree formulation for Zurich.