Taxonomic uncertainty exists regarding the circumscription of the following seven phenotypically similar Australian species: Poa crassicaudex Vickery, P. hookeri Vickery, P. labillardierei Steud., P. phillipsiana Vickery, P. poiformis (Labill.) Druce, P. porphyroclados Nees (including P. serpentum Nees) and P. sieberiana Spreng. Multivariate ordination and clustering analyses of morphological data were conducted and the distribution of morphological diversity among taxa was assessed for congruence with current taxonomic boundaries. One-way analyses of variance and Tukey’s honest significant difference tests were applied to identify continuous characters that differentiate taxa. Utility of morphological characters was assessed in light of the distribution of variation among and within taxa. Revisions of P. labillardierei, P. porphyroclados and P. sieberiana circumscriptions are proposed. Accounting for nomenclatural priority, proposed revisions include recognition of P. porphyroclados vars. acris, labillardierei, porphyroclados, and. serpentum, P. sieberiana var. cyanophylla Vickery at species rank, and P. phillipsiana at varietal rank within P. sieberiana. Species boundaries are supported by leaf, culm, panicle, spikelet and floret dimensions. The present study enables increased accuracy in taxonomic identifications for Poa species that are keystones in a range of grassland vegetation types, including critically endangered natural temperate grassland and eucalypt woody grassland ecosystems, therefore contributing to the effective biodiversity monitoring and management of these ecosystems.