We articulate and reflect on the use of nature as a physical sketching material. We have closely documented explorations of various organic and non-organic materials found during excursions in a local forest and how we used them as resources in sketching. This serves as an exemplar case of how sketching in interaction design can be grounded in empirical explorations of nature. We discuss three examples of sketching based on explorations and experiences with elements and objects from a forest. Processes and characteristics of phenomena in nature such falling leaves, melting and freezing of snow, and perennial growth allowed us to expand our design repertoire and sketching skills, especially as new forms of representations and interactions. Based on this we outline three aspects of how nature can be included in sketching processes: being in nature, bringing nature to the lab, and bridging nature and interaction design.