Approaching from an analysis of the work of Robert Brown (1773-1858) and Friedrich Welwitsch (1806–1872) on Rafflesia and Welwitschia, this article explores how the “natural method” became a tool for understanding extra-European flora in the nineteenth century. As botanists worked to detect “hidden affinities” between plants that would enable them to identify the so-called natural families to which even anomalous species belonged, they relied on comparison as their basic methodological procedure, making it essential for them to have access to collections. In their scientific writings, professional botanists tended to steer clear of any emphasis on plant exoticism. While botany engaged in dialogue with various types of approaches, the field essentially normalized the exotic. The article’s exploration of the hermetic style of scientific texts and the way botanists incorporated illustrators’ work sheds light on the complexity of the spaces where natural history was done, in a context where plants were circulating from around the globe.