Faced with the environmental challenges posed by climate change, architects are creating nature-based solutions for urban areas, such as transforming living trees into artificial architectural structures. In this study, we have analyzed stem pairs of five tree species conjoined for more than eight years by measuring the stem diameters below and above the resulting inosculation and by calculating the respective diameter ratio. Our statistical analyses reveal that Platanus × hispanica and Salix alba stems do not differ significantly in diameter below inosculation. However, in contrast to P. × hispanica, the diameters of the conjoined stems above inosculation differ significantly in S. alba. We provide a binary decision tree based on diameter comparisons above and below inosculation as a straightforward tool for identifying the likelihood of full inosculation with water exchange. Moreover, we have compared branch junctions and inosculations by means of anatomical analyses, micro-computed tomography, and 3D reconstructions showing similarities in the formation of common annual rings that increase the capacity for water exchange. Due to the highly irregular cell arrangement in the center of the inosculations, cells cannot be assigned clearly to either of the stems. In contrast, cells in the center of branch junctions can always be attributed to one of the branches.

Urban spaces are often dominated by paved surfaces and ongoing processes of densification; consequently, intensifying the urban heat island effect. In order to strengthen the liveability of urban spaces, an adequate amount of green spaces is needed. Trees in planters are an alternative greening solution; however, the lack of root space due to underground infrastructure poses a challenge. Furthermore, temporal aspects such as tree growth, tree death, and growth responses to environmental factors are frequently overlooked in projects that use trees in planters. In multiple case studies that employ the method “Research through Drawing” we analyse five selected projects, which deal in sharply contrasting ways with the temporal aspects of trees in planters. Our results show that promising approaches exist, albeit they are not described explicitly in either written or graphical form. Consequently, temporal aspects are only vaguely considered in the projects’ design concept. This results in the neglect of the further use of trees in planters in temporary projects, or in the disregard for tree death in the design and responses to it in permanent projects. Therefore, the potential of trees in planters as an alternative and complementary greening solution remain unexploited. To overcome this, a coherent temporal approach that considers growth, death of plant parts or whole plants, and that is developed as an integral part of the design concept and communicated graphically, would ensure that the involved actors and their respective tasks are well coordinated throughout the lifetime of a project.