In tidal marshes of the northeast US, replacement of native cattail (Typha angustifolia) by the common reed (Phragmites australis) is widespread, and reed is often the target of removal efforts. Reed sequesters nearly twice the amount of nitrogen per unit marsh area in living aboveground tissue compared to cattail. Microbial decay processes immobilize additional nitrogen or return this organic nitrogen to the pool of inorganic nitrogen. We compared microbial growth during decay of standing and fallen litter of cattail and reed. Shoots of both plants were collected at the time of peak live biomass and then periodically throughout litter decomposition. Litter was analyzed for mass loss, nitrogen content, and biomass and production of fungi and bacteria. There were statistically significant but small differences in litter-associated microbial biomass and production between these two plants. Microbial production on both litter types was dominated by fungi, accounting for > 99% of the total. Living fungal biomass (estimated from ergosterol) associated with reed and cattail litter averaged 6.1 and 8.2 mg fungal C/g litter dry mass, respectively, and fungal nitrogen accounted for roughly 25% of the total nitrogen associated with litter. Detrital nitrogen standing stocks/m² were greater for reed than cattail throughout the first 2.5 years of decay. Therefore, the ability of reed litter to support decomposer growth is only somewhat lower and nitrogen retention is greater than for one of the plants it replaces. These differences are probably insufficient to argue for aggressive control of reed in tidal wetlands.