Abstract: Can a difference in the heights at which plants place their leaves, a pattern we call canopy partitioning, make it possible for two competing plant species to coexist? To find out, we examine a model that relates the dynamical behavior and competitive abilities of plant populations to the structural and functional features of the plants that form them. We begin by formulating a single species version of this model from biological first principles and show how all plant properties work together to determine population persistence and equilibrium abundance. Then we present this formulation's straightforward extension to two competing species that interact only by their shared use of sunlight. This two-species model is described by a Kolmogorov system of integro-differential equations in which the specific growth rate function of each species is a functional of the vertical leaf profiles of both species. This model allows us to consider the role of canopy partitioning in determining the outcome of competition between two plant species that compete only for sunlight. We use implicit methods to show that, under certain conditions, the species' nullclines can intersect at most once, and that when they do intersect, coexistence is always stable. We also construct surfaces that divide parameter space into regions in which each of the various outcomes of competition occurs, and then study parameter dependence in the locations of these surfaces. We then determine the outcome of competition between two plant species that differ only in their vertical leaf profiles. This analysis shows that canopy partitioning is both necessary and sufficient for the stable coexistence of two hypothetical plant species that are described by our model.