Speciation research bridges the realms of macro- and microevolution. Evolutionary developmental biology (evo-devo) has classically dealt with macroevolutionary questions through a comparative approach to distantly related organisms, but the field later broadened in focus to address recent speciation and microevolution. Here we review available evidence of the power of evo-devo approaches to understand speciation in plants at multiple scales. At a macroevolutionary scale, evidence is accumulating for evolutionary developmental mechanisms giving rise to key innovations promoting speciation. At the macro microevolution transition, we review instances of evo-devo change underlying both the origin of reproductive barriers and phenotypic changes distinguishing closely related species. At the microevolutionary scale, the study of developmental variation within species provides insight into the processes that generate the raw material for evolution and speciation. We conclude by advocating a strong interaction between developmental biology and evolutionary biology at multiple scales to gain a deeper understanding of plant speciation.