How densely is the vegetation planted?
Many of the wetland plants used for constructed wetlands are aggressive colonizers and given plenty of nutrients, such as sewage wastewater, a constructed wetland will probably be filled with plants within two operating seasons. Constructed wetlands used for mitigation purposes or heavy metal removal may take longer to fully colonize if fertilization is not used. For constructed wetlands in the subarctic, I generally use a 30 cm by 46 cm planting grid when quicker colonization is desired.
