While DNA barcoding has been largely successful in differentiating animal species for over 15 years, the search for the most effective loci and evaluative methods for plants continues. DNA barcoding could be useful to conservationists in Hawaii, and elsewhere, where overlapping geographic ranges and morphologies of endangered and non-endangered plant species occur, preventing rapid and reliable identification for anyone other than taxonomic experts. Floras of young, oceanic islands are a particularly severe test of the utility of DNA barcoding, because rapid speciation often results in short time periods for diagnostic mutations to occur. Recently, however, methods using molecular characters and geographic range data, rather than genetic distance and monophyly, have shown some success in differentiating plant species in the Canary Islands. Utilizing this approach, in addition to distance and monophyly methods, we used four common DNA barcodes to test 21 lineages of Hawaiian plants at the nuclear ITS2 locus, nine lineages at each of the plastid loci trnH-psbA and rbcL, and eight lineages at the plastid locus matK using newly generated DNA sequences and sequences downloaded from Genbank. Results show low discrimination success within the same lineage with all methods of analysis. These results highlight the continued importance of taxonomy based on morphology, and point to the need for additional genomic resources if DNA barcodes are to be used to accurately differentiate plant species derived from recent speciation events.