Adaptive radiation is fundamental to the study of evolutionary biology, often producing stunning diversity and extreme phenotypes in a variety of environmental niches. Sometimes referred to as the “Darwin’s finches of the botanical world”, the plant genus Scalesia (Asteraceae) is a textbook example of adaptive radiation. With 15 extant species, Scalesia is the largest endemic plant genus of the Galápagos, and the larger species of these woody “daisy trees” play fundamental ecological roles and even form highland forests on the larger islands of the Galapagos archipelago. Species within the genus display a large variation in life habit and morphology. Most remarkable is their variation in leaf morphology, especially the lobed leaf phenotype that evolved several times in the genus. Lobed leaves are believed to be an adaptation to a hot and dry climate. Here we investigate the evolutionary dynamics of this group of charismatic plants using population-level data from 400 entire genomes of all 15 extant Scalesia species. To elucidate the adaptive radiation of Scalesia, we combine genomic data with leaf morphometric and transcriptomic data to investigate natural selection on the lobed leaf phenotype. We conclude that the leaf lobing phenotype in Scalesia evolved as independent parallel adaptations of key regulators in the KNOX I developmental pathway.