This chapter is about the aboveground plant communities and their associated microbial populations. These plant assemblages are the dominant visual components treatment marshes. The characterization of the wetland vegetative communities depends strongly upon the background discipline of the researcher. A taxonomist or phytosociologist is focused on the listing of the individual species that are present. An ecologist may well be concerned with the biological diversity and richness of the system, and the productivity and community dynamics. An aquatic botanist is likely to emphasize the functional details of plant physiology, and their adaptations to environmental conditions. An engineer may use only broad concepts of vegetation, to tie together data analyses and predictive modeling.