The common reed, Phragmites australis, has been a native component of North American wetlands for thousands of years.  However, the introduction of a non-native haplotype of P. australis over a century ago has resulted in its well documented expansion into a variety of North American wetlands.  To determine if the invasive nature of the non-native haplotype could be attributed to physiological differences, we investigated if photosynthetic differences exist between native and non-native P. australis haplotypes.  Photosynthetic parameters were measured on native (type F) and non-native (type M) P. australis haplotypes on both greenhouse-grown plants and in-situ on plants in a tidal marsh near Easton, MD using infrared gas analysis (IRGA) and pulse amplitude modified (PAM) fluorometry.  Field measurements were conducted monthly for two years from June through August.  Photosynthetic pigments were also quantified on greenhouse-grown and field plants using standard spectrophotometric techniques and HPLC.  Significant differences were observed between native and non-native P. australis haplotypes in both field and greenhouse grown plants.  Non-native P. australis contained significantly greater concentrations of chlorophyll a, chlorophyll, b, and total carotenoids than native P. australis plants.  Additionally, non-native P. australis plants demonstrated superior photosynthetic potential with significantly greater values of A_max and ETR_max.  These results demonstrate that native P. australis plants are physiologically different from the non-native invader, and suggest that the expansion of non-native P. australis into previously unoccupied habitats may be facilitated by its greater photosynthetic potential.