This week, let’s take a closer look at the most visible part of wetland ecosystems, which grows from hydric soils: wetland plants! Wetland plants can be called hydrophytes, aquatic plants, or macrophytes. They are species that can live in wet places, such as saturated soils, flooded soils, submerged in water, or on the water’s surface. Wetland plant species have the ability to thrive in wet and anaerobic (lacking oxygen) soil conditions due to physical or morphological adaptations, tolerances, and life history strategies.

Where a particular wetland plant lives is based on the amount of water that is present. Marshes usually have a gradient that moves from open water to saturated soils to drier upland soils. As the water levels change, so does the plant community composition.

Wetland plants play several important roles in a wetland ecosystem. Here are some of them:

1. Wetland plants are the base of the food web, providing both food and habitat for microbes, algae, insects, fish, birds, waterfowl, and mammals. The types of wetland plant species and the quantity of those species influence the overall diversity of a wetland community.

2. The plants impact the movement of both water (hydrology) and sediments. The plants can slow the water flow, reducing the effects of erosion and flooding, lessening the impact of waves, and stabilizing shorelines.

3. Wetland plants strongly influence water chemistry. They can uptake nutrients from the water and move compounds from the sediment into the water column. They can improve water quality by absorbing nutrients, metals, and other contaminants.

In our Smart Wetlands, the plants play a critical role in nutrient removal. It is not necessarily through nutrient uptake, as nitrogen removal by plants may account for only 12–14% of the total amount; however, they provide the substrate and food source for the microbes that are transforming nitrate into dinitrogen gas (N2). The plants also provide the carbon that serves as the food or energy source for the microbes. Finally, vegetation helps with slowing down the inflowing tile water, settling out any soil particles, and distributing the water as it flows from the inlet to the outlet.

The plants that thrive in a Smart Wetland are those species that can tolerate the high nitrogen loading from the tile water, establish quickly, reproduce at the designed water depths, and survive the changing water levels (0-36”) throughout the year. The Wetlands Initiative seeds or plants several different native species in our Smart Wetlands, as we want to establish resiliency in the wetland to the varying conditions as well as bring back the wildlife habitat benefits that come with a diverse plant community.

The Illinois native wetland plants that are appropriate for a Smart Wetland include arrowhead (Sagittaria latifolia), common threesquare (Schoenoplectus pungens), prairie cordgrass (Spartina pectinata), common or soft rush (Juncus effusus), hardstem bulrush (Schoenoplectus acutus), softstem bulrush (Schoenoplectus Tabernaemontani), dark green rush (Scirpus atrovirens), giant bur-reed (Sparganium eurycarpum), common water plantain (Alisma subcordatum), tussock sedge (Carex stricta), and blue-flag iris (Iris virginica var. shrevei). The names in bold are those that are recommended in the NRCS Conservation Practice Standard for Constructed Wetlands for Cropland Drainage Water Treatment (CPS 656). The practice standard also recommends broad-leaved cattail (Typha latifola), which we don’t recommend as this species can quickly overtake the entire wetland, essentially forming a monoculture, which requires much more management to control its spread. You learn more about these plants and other wetland plNts found in Illinoi at: https://www.illinoiswildflowers.info/wetland/wetland_index.htm 

Here are some images of beautiful and hard-working wetland plants from our Smart Wetlands.

Jill Kostel leads the project team as TWI's Senior Environmental Engineer and primary designer of Smart Wetlands. She also works to develop new partnerships to help spread constructed wetlands widely in Illinois.

Support for developing this blog was provided by the Mississippi River Network. Consider becoming a River Citizen to help “clean up and protect our country's greatest River.”