Many authors assert that plants exhibit complex behaviours which are analogous to animal behaviour. However, plant ecologists rarely root these studies in a conceptual foundation as fertile as that used by animal behaviourists. Here we adapt the optimality principles that facilitated numerous advances in the study of animal foraging behaviour to create one possible framework for plant foraging behaviour. Following the traditions of animal foraging ecology, we discuss issues of search and handling in relation to plant root foraging. We also develop a basic plant-centered model that incorporates modular growth and foraging currencies relevant to plant growth. We conclude by demonstrating how this new foundation could be adapted to address five fundamental questions in plant foraging ecology.