In Plant-Thinking: A Philosophy of Vegetal Life, Michael Marder asks how we can encounter plants as other than human: can we find a way to understand that plants “are capable, in their own fashion, of accessing, influencing, and being influenced by a world that does not overlap the human Lebenswelt but that corresponds to the vegetal modes of dwelling on and in the earth?” He grapples with how plants might escape “the objectifying grasp of metaphysics and its political-economic avatars,” which deny them “the core values of autonomy, individualization, self-identity, originality, and essentiality.” That said, as Marder himself recognizes, limiting oneself to Western metaphysics (as he does) excludes alternative modes of conceiving vegetal life. In particular, Marder does not engage with concepts of plant power intrinsic to premodern natural history and herbal medicine, which attribute “virtues” to plants.

“Virtue” is a complex word, encompassing the more familiar meaning of positive moral qualities, but also the sense of efficacy, both “a power inherent in a thing” or “a capacity for producing a certain effect.” When it comes to connecting virtue to plants, the Oxford English Dictionary narrows the scope to “power to affect the body in a beneficial manner; strengthening, sustaining, or healing power.” However, the OED has missed those texts that tell us that plant “virtue” may be deadly as well as beneficial.