In order to meet the definition of hydrophytic or wetland vegetation, the majority (>50%) of the dominant vegetation species on site must be classified as an obligate wetland plant, facultative wetland plant, or a facultative plant (excluding facultative minus). This requires the ability to identify plants down to species. This can be a difficult task especially when you try to identify sedges (there are 4,000-5,000 species of sedge in the world!). There are separate lists developed for each region of the United States. Click here to view a regional list.

In some circumstances instead of relying strictly on plant species, some secondary rules can be employed. Some example secondary rules include the following:

-Two or more dominant plant species exhibit morphological adaptations or have known physiological adaptations for survival in wetlands. (The former must be observed in most individuals of the dominant species). -Visual observations of plants growing in flooded or saturated soils for at least 10% of the growing season.