Common aquatic weeds in Louisiana

Christopher Mudge, Ribbeck, Anna

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Louisiana has a warm environment that allows many plants to thrive, including aquatic weeds. Aquatic weeds can cause environmental and ecological harm to Louisiana’s waterways, which include rivers, streams, lakes, swamps and ponds. Below are common aquatic weeds found in Louisiana and information on how to identify and manage them.



Giant Salvinia MicrosoftTeams-image 2png

(Salvinia molesta)

This floating invasive aquatic fern is native to South America and was introduced into the Toledo Bend Reservoir in the late 1990s. It has spread throughout most of the inland and coastal waterways of Louisiana. Giant salvinia is often confused with its close relative common salvinia (Salvinia minima). As this plant forms a thick mat, it blocks or limits light and oxygen into the water column; alters or lowers water pH; displaces native plants, fish and wildlife; and hinders water use for recreation, irrigation and navigation purposes. View this video for identification and management information: https://bit.ly/SalviniaControl.





Common SalviniaCommon Salviniapng

(Salvinia minima)

The nonnative common salvinia is a floating aquatic fern that has been in Louisiana for a number of years and is less aggressive than its close relative giant salvinia (Salvinia molesta). The plant remains as a single layer on the water surface, whereas giant salvinia forms a mat several plant layers thick. View this video for identification and management information: https://bit.ly/SalviniaControl.





Water HyacinthWater Hyacinthpng

(Eichhornia crassipes)

The perennial free-floating aquatic plant was introduced into Louisiana in the late 1800s and was the most problematic species until the introduction of hydrilla and giant salvinia. Water hyacinth spreads rapidly by producing daughter plants, and the mats of plants can double in size in as few as six days. Similar to giant salvinia and water lettuce, water hyacinth forms impenetrable mats that hinder recreation, navigation, and other water uses and reduces biodiversity by crowding out native plants. Established populations of water hyacinth degrade water quality for fish and other species. View this video for identification and management information: https://bit.ly/WaterHyacinthControl.





HydrillaHydrillapng

(Hydrilla verticillata)

This invasive submersed aquatic plant was introduced into Louisiana in the 1970s. The aggressive weed rapidly forms a surface mat, which limits or blocks light to the lower water column; alters water oxygen and pH; displaces native plants, fish and wildlife; and hinders water use for recreation, irrigation and navigation purposes. View this video for identification and management information: https://bit.ly/HydrillaControl.





DuckweedDuckweedpng

Common duckweed (Lemna minor), dotted duckweed (Landoltia punctata) and giant duckweed (Spirodela polyrhiza) are found throughout Louisiana. Although the impact of duckweed species can be less negative than other noxious or invasive species, these plants can grow into dense surface mats that block light penetration into the water column and ultimately create stagnant aquatic systems, especially in ponds, ditches and slow-moving bayous and small lakes. View this video for identification and management information: https://bit.ly/DuckweedControl.





Water LettuceMicrosoftTeams-image 4png

(Pistia stratiotes)

This free-floating aquatic plant resembles a floating open head of lettuce. Similar to other floating species, water lettuce clogs waterways, thus limiting recreational water use, interfering with oxygen exchange and light penetration, and altering habitat for plants, fish and wildlife species. View this video for identification and management information: https://bit.ly/WaterLttuceControls.





Cuban BulrushCubanBulrushpng

(Cyperus blepharoleptos)

The emergent, epiphytic sedge plant was introduced into Louisiana around 2011 and has become more problematic each year. During the initial growth stages, Cuban bulrush requires another floating species, such as giant salvinia or water hyacinth, to provide support for establishment and mat formation. However, as the plant matures and forms an extensive network of runners and roots/rhizomes, it becomes buoyant. At this stage, the host is no longer needed, and Cuban bulrush survives as its own free-floating mat. View this video for identification and management information: https://bit.ly/CubanBulrushControl.





Crested Floating HeartCrestedFloatingHeartpng

(Nymphoides cristata)

Crested floating heart was introduced into Louisiana in the late 2000s and is quickly spreading. It is one of seven Nymphoides species present in the U.S. that has escaped from the ornamental plant trade over the years. The plant can be found rooted into the sediment growing in water several feet deep or as free-floating plant. View this video for identification and management information: https://bit.ly/CrestedFloatingHeartControl.





Southern NaiadSouthernNaiadpng

(Najas guadalupensis)

In general, this plant is a desirable native species in the U.S. However, the submersed species can become a nuisance to homeowners and end-users in smaller systems once the plant is established and has no competition from other plant species or consumed by wildlife. View this video for identification and management information: https://bit.ly/SouthernNaiadControl.




LSU AgCenter illustrations by Matt Faust

8/11/2021 4:36:14 PM
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