Tabebuia karsoana is a shrub or small tree species from the northern karst of Puerto Rico, where it is confined to ridges and hilltops. Its habit and general flower appearance are similar to those of T. haemantha (Bertero ex Spreng.) A. DC. However, T. karsoana is distinguished by leaflets densely covered with white peltate scales on both sides, the corolla fuchsia with a white microscopically papillose throat, the stamens with arcuate filaments, and the anthers divaricate and connivent, among other features. In addition, the two species' distributions do not overlap and their habitats are contrasting. According to IUCN criteria, the new species can be defined as "endangered" and consequently needs legal protection. © The Board of Trustees of the Royal Botanic Gardens, Kew, 2009.