The effect of four levels of ammonia concentration on the biomass production of Sagittaria latifolia (arrowhead), Phragmites australis (common reed), Scirpus acutus (bullrush), Typha latifolia (cattail), and Juncus roemerianus (common rush) was studied using field scale constructed wetland ponds of 3.05 x 0.6 m. These species of plants are common in constructed wetlands treating animal waste lagoon effluent. Twenty ponds were constructed to accommodate the five species and four ammonia levels. The experiment had three repetitions in time. Effluent from the second cell of a two cell anaerobic lagoon system treating flushed swine waste was utilized at four dilution levels, providing mean ammonia concentrations of 20.5, 41.1, 61.6 and 82.4 mg NH3-N/L for the study. Biomass production was determined by harvesting the plants at specified time intervals and measuring dry weight production. The ponds were operated as standard constructed wetlands with a water depth of 10-15 cm. After the 3 month field study was completed, statistical analysis of the data was performed. This analysis showed that the only species affected by ammonia concentration was Scirpus acutus. The remaining four species were statistically unaffected. Darn from the study also shows a significant difference in the biomass production between species.