An example of a floating wetland in a residential stormwater pond
Clare Escamilla, ©2024, Clemson Extension
Floating wetlands are buoyant platforms that allow plants to grow in water that is typically too deep for them. Plants can grow above the water level on the mat while their roots extend directly down into the water column. They can be installed in lakes, ponds, and other slow-moving waterbodies. Floating wetlands can help reduce nutrient concentrations in the waterbody where they are installed, while also providing other potential benefits. To learn more about floating wetlands and their potential water quality benefits in stormwater ponds, see An Introduction to Floating Wetlands for Stormwater Ponds.
Floating wetlands are typically considered low-maintenance and are often left to naturalize on the waterbody where they are planted. However, if the waterbody is highly visible in a public space, then periodic maintenance may help ensure the visual appeal of the wetland. In addition, some maintenance throughout the year can help to permanently remove nutrients from the waterbody and can make harvesting your wetland more manageable.
General Maintenance
Since the roots of floating wetland plants are constantly submerged in water and can take up nutrients from the water directly, a floating wetland does not need any supplemental irrigation or fertilizer application. While these aspects make maintenance of a floating wetland easier, there are some aspects of floating wetland maintenance that are more cumbersome. To remove weeds, debris, or dead plant material, someone must either paddleboard/canoe/kayak/boat to the wetland or set up a system to pull the wetland to the bank to perform maintenance along the bank. Since a mature floating wetland can be very heavy and bulky, it is recommended that at least two people are present to perform maintenance – if not more.
Recommended maintenance for floating wetlands includes cutting the shoots of plants to just above the crown at least once a year, preferably in late fall, to prevent dead and decaying plant material from falling into the water and re-introducing nutrients1. While a naturalized floating wetland can look great and provide habitat for surrounding wildlife, depending on local aesthetic preferences, communities may want to cut and trim plant species a few times a year to provide a less natural (more manicured) appearance. After several years of growth, selected plants can also be removed to create space on the mat to encourage new plant growth1.
Maintaining a floating wetland by canoe
Clare Escamilla, ©2024, Clemson Extension
Maintaining a floating wetland by pulling the wetland to the side to perform maintenance from the bank.
Sarah White, ©2024, Clemson Extension
Weed Management
As a reminder, herbicides and fertilizers should not be applied to floating wetlands. If applied, these chemicals have the potential to enter waterbodies and negatively impact water quality. Volunteer plant species (generally considered weeds) may colonize the floating wetland due to seeds dispersed from surrounding vegetation or carried in by wildlife that visit the wetland. While volunteer species may not be part of the original floating wetland design, they can still contribute to nutrient removal efficiency and are typically well adapted to the chemical and climatic conditions of the pond and community. If the species becomes a nuisance and begins to dominate the wetland or a non-native species appears, then weeds can be pulled by hand. Weeds can quickly get out of control; therefore, it is good to visually monitor the floating wetland on a regular basis to catch these species early so it is easier to hand weed.
Photo of floating wetland.
Clare Escamilla, ©2024, Clemson Extension
Photo of the same floating wetland 3 months apart shows how quickly volunteers can colonize if not frequently monitored and maintained.
Clare Escamilla, ©2024, Clemson Extension
Replanting harvested floating wetland plants along the bank of the pond.
Amy Scaroni, ©2024, Clemson Extension
Floating Wetland Harvest
Harvesting a floating wetland involves either removing the whole plant and mat from the waterbody or simply removing the above mat plant tissues. Some floating wetland maintenance professionals have equipment that enables trimming of roots and shoots, leaving plant crowns and root systems to regrow. Harvesting a floating wetland can help prevent nutrients that have been taken up by plants from being cycled back into the water system when plants senesce. It also helps remove old and dead plant material that could fall into the water and potentially fill the bottom of the pond or release nutrients2. Pruning and removing the above mat plant material can allow plants to reallocate nutrients to above-ground shoot growth and, therefore, increase nutrient uptake by the floating wetland2.
Harvest of plant material is typically performed in early fall before winter die-off. If whole plants are harvested from the wetland, they can be replanted along stormwater pond banks as a vegetated buffer or replanted in other landscapes. Plant materials can also be used as feed for cattle or used in some craftwork3. Floating wetlands can be harvested annually or after several years; however, without periodic maintenance, floating wetlands can become overgrown, which makes harvesting and salvaging plant material for reuse very difficult.
References
- Powell B. Floating wetlands: container gardens for your pond factsheet. Clemson (SC): Clemson Cooperative Extension; 2012 Sep. HGIC 1857. https://hgic.clemson.edu/factsheet/floating-wetlands-container-gardens-for-your-pond/.
- Colares GS, Dell’Osbel N, Wiesel PG, Oliveira GA, Lemos PHZ, da Silva FP, Lutterbeck CA, Kist LT, Machado EL. Floating treatment wetlands: a review and bibliometric analysis. Science of the Total Environment. 2020 Apr;714:136776. doi:10.1016/j.scitotenv.2020.136776.
- Olguin EJ, Sanchez-Galvan G, Melo FJ, Hernandez VJ, Gonzalez-Portela RE. Long-term assessment at field scale of floating treatment wetlands for improvement of water quality and provision of ecosystem services in a eutrophic urban pond. Science of the Total Environment. 2017;584(585):561–571.
Originally published 11/24
