The too-common reed? Invasive phragmites can cause serious environmental problems
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EmailNative phragmites is also common across the Great Lakes, but it can help the environment. It’s important to know the difference between the two species.
Two types of common reed can be found across the Great Lakes basin. One is invasive and one is native - but both are called phragmites. Both are common across all eight Great Lake states. This abundance has gained a lot of attention about the negative impacts this invasive species (Phragmites australis subsp. australis) are having on ecosystems across the basin. However, the native phragmites (subsp. americanus) can be beneficial. This native species filters water and provides habitat for other plants and animals. The invasive one, on the other hand, can have serious negative environmental impacts. This is especially true if the species is left unmanaged.
How do we tell the difference?
The native and invasive subspecies are similar in many ways. However, they do have some key differences that can help us tell them apart. When distinguishing between them, it is important to use multiple factors due to the high number of shared characteristics as can be seen in the photo.
Table 1. Key characteristics for distinguishing between native and invasive Phragmites australis.
|
Characteristic |
Invasive |
Native |
|
Stem |
Rougher textured stems with dull tan color |
Smoother stems with red color |
|
Leaves |
Darker bluish gray-green leaves |
Lighter yellow-green leaves |
|
Leaf sheath |
Leaf sheath adhere tightly to culm (reed-like stem) and does not peel off |
Leaf sheath adheres less tightly and peel back and falls of culm (reed-like stem) |
|
Rhizomes |
Rhizomes rarely exceed 15 mm in diameter and are darker yellow |
Rhizomes are lighter color |
|
Stands |
Denser stands |
Less dense stands |
|
Biodiversity |
Monocultures |
Polycultures |
Invasive phragmites found in 49 states
The invasive phragmites is estimated to have been introduced in the eastern United States in the late 1700s to early 1800s.It can now be found in all 49 mainland states. It was first reported in the Great Lakes basin in Pennsylvania in 1828.Since then it has since been found in all eight Great Lakes states and Ontario. It can range from 7-20 feet in height with a long hollow reed-like stem. The blue green leaves are flat and drooping. They range in sizes of 8-24 inches long and 3-13 inches wide.
Under the earth, invasive phragmites has a dense root/rhizome network that can be up to 7 feet deep. The plant is able to spread through both underground soil rhizomes and above ground runners reaching up to 10 feet. The flower heads are oblong and purplish in color when young. They become a straw color once the plant reaches maturity. Flower heads can range from 6-20 inches long and 2-8 inches wide. Seeds are very small and develop small hairs when they mature making them“fluffy” with a gray sheen.
What’s wrong with too much phragmites?
Invasive phragmites impacts the Great Lakes by causing negative environmental, social, and economic problems. It can take over an ecosystem through its dense plant stands, which can prevent other species from being able to grow in the same area. It also negatively impacts wetland wildlife habitats. Additionally, the invasive plant outcompetes native plants by releasing chemicals in the soil that can keep other plants from growing.
The tall dense plant stands can block access to coastal shorelines and reduce the amount of native fish and wildlife. This can decrease the recreational value of land for birders, fishers, and other recreational users. The tall stands can also block coastal views, decreasing property values and creating a safety hazard for drivers. However, it is not all bad: Phragmites can also filter the water to remove excess nutrients, create habitats for organisms, and stabilize the soil to prevent erosion. But overall, the bad outweighs the good for the invasive subspecies, making it an important plant to monitor and manage.
Above- and below-ground methods
There are some ways to help prevent the spread of this invasive plant and promote native populations. Managers can use a combination of biological, physical, and chemical tools to manage invasive phragmites. It’s important that any methods are used at the right time and focus on the plant above the ground and the root systems below. Biological controls, including 164 insects, 7 mites, and 30 fungi, are currently being used outside of North America but are not approved for use in the United States.
Research at Cornell University is focusing on rhizome-feeding insects, which may destroy the underground rhizomes. Insects can reduce underground energy stores instead of just removing the plant which could increase long-term effectiveness. Grazing animals are another biological control that focuses on the plants above ground, they do not kill the plant but only reduce its density. If done at the wrong time, this practice can actually increase growth instead of depleting it.
Physical management options include
- Controlled burns and repeated cuttings. However, both of these methods only address aboveground biomass and do not remove the rhizome/roots. This can result in continued germination and if done at the wrong time can even stimulate growth.
- Physical measures are best paired with chemical ones that focus on killing the root/rhizome. Glyphosate and imazapyr are two current broad spectrum herbicides that, when properly applied together, can reduce biomass by more than 90%. As is true with all of the methods, chemical treatments are non-selective and may harm other species. It is essential that they are used correctly to ensure other species are not harmed.
Stop the spread
Property owners and residents can help stop the spread of invasive phragmites by reporting sightings to the Midwest Invasive Species Information Network (MISIN), through their website or their mobile app. You can also report any sightings to the Nonindigenous Aquatic Species (NAS) program through their Sighting Report Form. Through combined efforts between researchers, natural resource managers, and community members we can slow down the spread of this invasive species and conserve the Great Lakes ecosystems across the basin.
Learn more about this species through its online profile at the Great Lakes Aquatic Nonindigenous Species Information System.
Michigan Sea Grant helps to foster economic growth and protect Michigan’s coastal, Great Lakes resources through education, research and outreach. A collaborative effort of the University of Michigan and Michigan State University and its MSU Extension, Michigan Sea Grant is part of the NOAA-National Sea Grant network of 34 university-based programs.
This article was prepared by Michigan Sea Grant under award NA180AR4170102 from the National Oceanic and Atmospheric Administration, U.S. Department of Commerce through the Regents of the University of Michigan. The statement, findings, conclusions, and recommendations are those of the author(s) and do not necessarily reflect the views of the National Oceanic and Atmospheric Administration, the Department of Commerce, or the Regents of the University of Michigan.
