Podostemum ceratophyllum (Podostemaceae), “Hornleaf riverweed,” is a native aquatic flowering plant that occurs only attached to rocks in fast flowing water. The species occurs in much of eastern United States and Canada. Over the last several decades the species has notably declined in numbers, largely as a result of human induced factors. The ecological importance of P. ceratophyllum in rivers is well documented. This research is the first attempt to transplant the species into a river where it was not known to occur, with the goal of helping to mitigate the loss of populations. The plant was taken from two “donor” rivers where the species grows naturally, and moved into the Norwalk River (Wilton, CT), as well as between the two donor rivers. Relative growth rate was significantly impacted by the location the plants were moved to, but not by the source (donor river) plants were moved from. Transplanted P. ceratophyllum grew in each of the three rivers, although growth rate was significantly lower in the Norwalk River. Within the Norwalk River, plants from neither source had a significantly different growth rate, suggesting that the location plants grow in is more important than the river they are moved from. Results from one field season show that the methodology used to transplant P. ceratophyllum was successful, as the plants survived and grew during the 4-5 month period. Future studies will investigate causes of lesser growth in the Norwalk River, and improve upon the methodology used.