This paper chronicles and reflects on the processes and the meanings of a project of speculative design that creates a narrative based on the scientific notion of phytomining, the activity of extracting metals from the soil using plants. The paper reflects on the ability of the project of bringing together people from different expertise, as a successful case study of Speculative Design and Research through Practice. Besides the scientific and technical challenges posed by GeoMerce, the authors of this paper reflect on the critical framework that set the basis for such a complex project.