•Whole genome duplications are an important mode of plant evolution.•Plants evolve developmental novelties by retention of duplicated control genes.•Genes controlling transcriptional networks are correlated with morphological complexity.•Both ancient and recent paralogs play important roles in the evolution of plant development. Most duplicated genes (paralogs) are quickly erased during evolution, and only some are retained. Yet, gene and genome duplications are connected to the evolution of genetic and, in turn, morphological complexity. Plants are especially prone to experience polyploidizations and to enhance their gene repertoire after such events. Genes encoding proteins involved in transcriptional regulation are of especial interest since they are correlated with the occurrence of genome duplication events and with the rise of plant morphological complexity. Here, I review what we know about paralog retention as a driver for morphogenetic evolution of plants. The main focus is on the evolution of plant genes controlling development (morphogenetic transcription factors).