Species delimitation is challenging in New Zealand Plantago because of a complex polyploid evolutionary history, few taxonomically useful characters due to reduced habit and wind-pollinated flowers, and phenotypic plasticity. To clarify species limits and revise the taxonomy of this group, analyses of novel morphological data were undertaken and evaluated alongside previously published studies of chromosome number, amplified fragment length polymorphisms, molecular phylogenetics, molecular cytogenetics, and morphology. All 11 native species of Plantago recognized here are endemic to New Zealand, except Plantago Orianthi which is also native to Tasmania, Australia. In contrast to previous treatments, Plantago picta is recognized here at the species rank, Plantago masonite is treated as a synonym of Plantago triandra, and one new 16-diploid species, Plantago udicola Meudt & Garn.-Jones, is formally described. Seed number and shape, scape, bract and sepal vestiture, and a number of flowers and spikes are particularly important characters for species delimitation.
