Acacia verniciflua A.Cunn. and A. leprosa Sieber ex DC. are believed to be closely related, although strict interpretation of the current sectional classification of subgenus Phyllodineae places them in separate sections based on main nerve number. Six populations, comprised of the common and the southern variants of A. verniciflua and the large phyllode variant of A. leprosa, were sampled to test the value of nerve number as a taxonomic character and the current delimitation of these geographically variable species. Morphometrics, microscopy and the AFLP technique were used to compare and contrast populations. Phyllode nerve development was investigated and the abaxial nerve was found to be homologous with the mid-rib of a simple leaf. Three taxa were differentiated, two that are consistently two-nerved and one taxon that is variably one-nerved, two-nerved or both within a single plant. The first two-nerved taxon, characterised by smaller phyllodes, matches the type specimen of A. verniciflua. The second two-nerved taxon, characterised by large phyllodes, is apparently endemic to Mt William. The third taxon, with variable main nerve number, also has large phyllodes, and combines large phyllode variant A. leprosa (Wilhelmina Falls) and southern variant A. verniciflua (Kinglake) individuals. The number of main nerves per face in phyllodes is not a useful taxonomic character for sectional classification of Acacia. Although it has clearly proved functional in some instances, the character appears too variable to reliably define natural monophyletic groups. Anatomical features such as cell number of resinous glands and staining patterns proved to be informative.