The terms “cosmopolitan” and “invasive” name ideas that have long figured prominently in the practices, the methods, and the unexamined assumptions of Victorian studies. These categories also shape the study of plants, both now and in the nineteenth century, along with related terms like “native,” “exotic,” and “hybrid.” “Invasion biology,” for example, currently describes the study of how nonnative species spread around the world, and the phrase “nativism-cosmopolitanism dichotomy” has been used to describe the impasse between different approaches to global plant distribution and migration. This paper will put these variable disciplinary conceptions of “cosmopolitan” and “invasive” into conversation with each other, offering a methodological reflection with the goal of clarifying their meanings and applications in and for current scholarship of the Victorian period. If ecological uses of these ideas, like aesthetic and political uses, are rooted in the nineteenth century, their disparate strands have not yet been sufficiently disentangled. What difference does it make to speak of invasive plants as compared to human invaders? How does our sense of cosmopolitanism, empire, and invasion change when pressure is exerted from other fields? Perhaps most importantly, what are the ethical dimensions of these concepts, especially when nonhuman entities are included?