In this article, I argue that the French philosopher René Descartes was far more involved in the study of plants than has been generally recognized. We know that he did not include a botanical section in his natural philosophy, and sometimes he differentiated between plants and living bodies. His position was, moreover, characterized by a methodological rejection of the catalogues of plants. However, this paper reveals a significant trend in Descartes's naturalistic pursuits, starting from the end of 1637, whereby he became increasingly interested in plants. I explore this shift by examining both Descartes's correspondence and several notes contained in the Excerpta anatomica. Grounded in direct observations, Descartes's work on vegetation provides a modest, though not unimportant, contribution to a natural-philosophical approach to the vegetal realm. This had a direct bearing on his lifelong ambition to explain the nature of living bodies and also fuelled the emergence of botany as a modern science.