This ethnographic study of North American herbalists’ teaching practices is informed by nearly two years of in-depth fieldwork grounded in participant observation at “The Center,” a school of clinical herbalism in Vermont. At The Center, teachers understand human health as reliant on human relationships with what they call “obligate ecologies”—that is, the ecological others and places to which humans must practice accountability in order for all to thrive. They frame the work of accountability through language of “connection,” “communication,” and “friendship” across species, especially between plants and people. This dissertation argues that by teaching how to be a “friend to the plants,” herbalists enable students to imagine the entanglements of plants, people and environments, and then to act with reference to those relationships. Using ethnographic and historical methods to understand their direct sensory engagement with plants, I analyze their efforts to cultivate attentive relations across species as part of herbalists’ practices of care. Although the tools for critical analysis of what both “health” and “care” mean are available, provided by social and historical studies of technology and medicine, few studies to date have offered an in-depth analysis of health practitioners whose frame for teaching health care for humans also necessarily involves teaching care for relations with other-than-humans and environments. I offer a sustained engagement with the production of contemporary western herbalism as an “alternative” knowledge-practice to biomedicine. I position both the historical production of western herbalism, and the contemporary practices of teaching and learning it, in the context of the United States’ enduring the legacies, and ongoing practices, of settler colonialism and its entailments. And I unearth the ways that herbalists learn to care for human bodies because they learn to attend to, and care for, plants as friends and kin. I suggest that their pedagogies and practices lay bare American modes of knowing, encountering, and producing personal and environmental health today.