A model is presented describing above-ground biomass production for a monospecific community of common reed (Phragmites communis Trin.), a perennial which is characteristically found in wetlands. The approach used follows the classic method applied to crop plants, namely the determination of stand phenology, and the establishment of the relationships governing leaf area production, light energy absorption by the leaves, and conversion efficiency of absorbed energy into biomass. The model also needed to take into account remobilisation of reserves accumulated in the rhizomes, which ultimately form a significant proportion of accumulated above-ground biomass. The final model was rested over two consecutive years, and produced promising results with regard to both the levels of production attained and the kinetics of the processes involved. The model can be used to determine production potential under given climatic conditions in its current form, and could even be applied to plant canopies with analogous biological characteristics, although scope remains for additional refinements.